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Publication of this paper has been assisted by a grant from the Victoria University of Wellington Publications Fund. Material described here was in part assembled with the aid of a grant, enabling travel to Australia, from the Victoria University of Wellington.
Fifteen species, referred to ten genera, are present in a large collection of congrid leptocephali taken from around New Caledonia, Australia and New Zealand. These species are Leptocephalus Ariosoma Scheelei (Strömman), L. A. Mauritianum (Pappenheim), L. A. anago (Temm. and Schleg.), L. ?Alloconger anagoides (Bleeker), L. Conger wilsoni (Bl. and Schn.), L. C. verreauxi Kaup, L. C. cinereus cinereus Rüppell and L. Scalanago lateralis Whitley; the remaining seven, six of which are described as new species of Leptocephalus, cannot here be finally referred to known adult species but their larval pigmentation suggests that they belong to a further six genera. The adult of L. Ariosoma mauritianum spawns off both west and east Australia, that of L. Scalanago lateralis off west Australia only, while the majority of the other congrids represented in this collection probably spawn north of New Caledonia.
Conger wilsoni is a slender eel with 141–149 vertebrae, eye 1.9–3.9 per cent of total length and a dorsal origin well behind pectoral tip; C. verreauxi is more robust with 157–165 vertebrae, eye 1.2–1.9 per cent of total length and a dorsal origin over the pectoral tip.
Keys to the adult congrid genera and species in New Zealand waters and to the larvae in the southwest Pacific and Western Australia are given.
An earlier account (Castle, Gnathophis (Congridae) in Australasian waters from a large collection of over 1,000 specimens of various eel larvae assembled from west and east Australia, New Caledonia and New Zealand. The gnathophid leptocephali in this collection number some 250 while another 250 are larvae of other genera of congrid eels. These congrid leptocephali therefore make up almost half of the total collection. This paper describes the balance of the congrid larvae which are referred to ten genera and 15 species. Six of these species cannot with finality be assigned to any particular adult species or to any known species of Leptocephalus and are described as distinctive congrid larvae. In this study it quickly became obvious that there is an inadequate knowledge of the Indo-Pacific congrid fauna. The absence of information on vertebral counts for most adult species often prevented final identification of larvae. The adults of the two species of Conger in New Zealand waters are relatively common but are in need of definitive descriptions to complete the knowledge of the systematics of the New Zealand Congridae which has already been initiated (Castle,
I am greatly indebted to the following institutions for the loan of material:—the Centre d'Océanographie do l'Institut Français d'Océanie, Nouméa, New Caledonia; the C.S.I.R.O. Division of Fisheries and Oceanography, Cronulla, N.S.W., Australia; the Australian Museum, Sydney; the Western Australian Museum,
Asano (Anago Jordan and Hubbs, Ariosoma Swainson, Alloconger Jordan and Hubbs, Chiloconger Myers and Wade, Rhynchocymba Jordan and Hubbs, Gnathophis Kaup, Rhynchoconger Jordan and Hubbs, Japonoconger Asano, Bathycongrus Ogilby,
Included in this group of larvae in the collection are five species, three of which are referred to Ariosoma Swainson, Alloconger Jordan and Hubbs, Chiloconger or Anago (if indeed the latter is distinct from Ariosoma). There is therefore the possibility of a further genus in this subfamily, that this last species may belong to Anago, or that there is a further unknown species of Chiloconger. Leptocephali of the three genera are quite distinct in the distribution of chromatophores, but within Ariosoma with its three species described here only differences in numerical characters serve as specific characters. The same is true of other groups of leptocephali, not only of the Congridae. There are clear divisions in respect of pigment distribution enabling identification usually at the generic level and specific identification rests on numerical characters.
Although there has been difficulty in establishing conclusively whether Muraena balearica De Laroche, Muraena mystax De Laroche, Ariosoma, as I have already noted (A. balearica. Larvae of this species are well known from the central Atlantic and have been adequately described allowing me to recognise that closely similar larvae, differing only in the number of myomeres, occur in the present collection from the Australasian region. On the basis of the similarities, especially in the arrangement of pigment, these leptocephali are referred to Ariosoma.
The Ariosoma larvae fall readily into three clearly-defined groups with 110–119, 134–153, and 157–172 myomeres respectively. Ancona (Ariosoma larvae with about 115 myomeres to Temminck and Schlegel's Conger anago. Ancona confirmed this on the basis of a transitional specimen which had 119 myomeres. As Asano has shown ("Conger" anago has 149–159 vertebrae so that both Ancona and Gopinath were in error and their specimens clearly belong with the first group of larvae with 110–119 myomeres listed above from the present collection. Temminck and Schlegel's species, referred at present to Anago Jordan and Hubbs, Anago bears a striking resemblance to Ariosoma (Asano, Ariosoma. It is unknown at present whether Ariosoma possesses these structures. The single specimen referable to Ariosoma which I have in hand from Lord Howe Island is in such poor condition that I am unable to check for the presence of myorhabdoi.
Species of Ariosoma occur widely in the Atlantic from the Mediterranean to the Caribbean, in the Indian Ocean from the Red Sea to Natal and Malaya and in the Pacific from Lord Howe Island in the south to the west coast of Central America with the addition of China and Japan should Anago be proved a synonym of this genus. A number of species have been assigned, over the years, to Ariosoma but some of these will undoubtedly be placed finally in species of genera of the Congrinae, the adults of which bear at least a superficial resemblance to Ariosoma. A few of the known valid species have the following vertebral counts: A. balearica with 123–137, from the Central Atlantic and Mediterranean; A. gilberti (Ogilby, A. howensis (McCulloch and Waite, A. (=?Anago) Anago with 149–159 from the coasts of Japan and China.
Material Examined: Centre d'Océanographie de l'Institut Franç ais d'Océanie Collection (64 Specimens): 15.1mm total length, IFO Station 7–5, 22° 35′ S, 166° 16′ E, Alepisaurus ferox; 154.8, St S.11, 21° 31′ S, 164° 48′ E,
Australian Museum Collection (2 Specimens): 119.2, Aust. Mus. regd. no. IB.3999, Collaroy, New South Wales,
Western Australian Museum Collection (1 Specimen): 85.8, Accession No. P5172, 49 miles west of West End, Rottnest Island, Western Australia,
Description: 67 specimens: total lengths 15.1mm-154.8mm, myomeres 110–119, dorsal and anal fin-rays greatest in number in the longest specimen, 102 and 106 respectively. Description made from a full-grown specimen, IFO St 7–2 (measurements in mm): total length 105.0, head 3.3, snout 1.2, eye 0.8, cleft of mouth 1.5, postorbital 1.5, pectoral 0.9, snout-vent 100.0, predorsal ca. 98.5, depth just before eye 1.7, at pectoral origin 2.7, at midpoint between pectoral and vent 12.3, at vent 4.3. Branchiostegal and pectoral rays not developed, dorsal rays 77, anal rays 67, caudal rays 3 + 3 + 1. Teeth Myomeres 105 + 10 = 115. a–d = ca. 2. 1st vertical blood vessel at myomere 18, last at 58. Anterior margin of gall bladder at myomere 22.
Body moderately elongate, much compressed except along head, its depth about eight times in total length, tapering equally in front of, and behind, the midpoint of the body. Head very short, about 30 in total length, with the throat indented so that the head is clearly differentiated from the trunk; snout conical, about 3.0 in head, its dorsal profile slightly convex; nasal organ large, close in front of eye, with the nostrils not yet developed; eye small, 4.2 in head, round; cleft of mouth oblique, extending to below middle of pupil: teeth in both jaws acute but rather broad-based; an anterior grasping tooth in each jaw followed by a single series of teeth which gradually diminish in size posteriorly. Pectoral fin short, about 2.0 in postorbital, delicate, rounded; dorsal and anal fins with poorly developed rays, dorsal originating only a little in advance of level of vent, caudal with well developed hypurals and fin-rays.
Pigmentation in preservative as follows:—below the midlateral level on each myoseptum from the third to the last an oblique line of minute, compact, oval somatic chromatophores few in number anteriorly but increasing to about 16–20 in the middle of the body, decreasing in number along the caudal region; from the fifth segment to the origin of the dorsal fin a series of relatively large somatic chromatophores, 1–2 on each segment, along the dorsal midline; from the pectoral region to the posterior margin of the gall bladder on the body wall of the ventral midline, a regular series of small, compact chromatophores, 6–8 to each segment; posterior to this series, continuing to the vent, a paired, regular row of very small, dense, splanchnic chromatophores on the dorsal aspect of the intestine, about 12–14 for each segment; scattered small spots on the basal portions of many of the dorsal and anal fin-rays; a few spots over the base of the caudal fin; chorioid pigment present.
Remarks: The group of specimens described above agrees well with Strömman's 140mm specimen of L. scheelei from the Timor Sea, redescribed by Bertin (
Weber's specimen of L. indicus (L. Ariosoma scheelei), spots on the bases of the dorsal, anal and caudal rays and 115 segments of which 73 are preanal. There are no larval teeth but a few definitive teeth are present. These characters suggest that the specimen is a metamorphosing specimen of L. Ariosoma scheelei. The present collection contains three specimens which are at metamorphosis, 119.2mm, 126.3mm and 131.0mm total lengths, all of which have about 80 preanal myomeres and are probably at a slightly earlier stage than Weber's specimen.
The same author describes as L. taenia Lesson, 34 specimens of L. Ariosoma scheelei from the Banda Sea and neighbouring areas. These larvae, 56mm–124mm in length, have about 115 segments, the vent is essentially subterminal and the pigmentation is similar to that found in Strömman's L. scheelei although Weber makes no mention of pigment on the dorsal midline. I am satisfied, nevertheless that these leptocephali are L. Ariosoma scheelei. On the other hand, a small specimen, 19.5mm total length, which Weber also refers to L. taenia lacks the characters which are possessed by L. Ariosoma scheelei of equal size. There are 106 myomeres, there is no pigment except in the chorioid but the vent is very close to the end of the body. Although in such a small specimen errors may be made in counting the posterior segments, specimens of L. Ariosoma scheelei
Gopinath (Congrellus anago. These specimens were 110mm–158mm total lengths with about 115 myomeres and they have pigment as in L. Ariosoma scheelei. So far as I can determine from his account all of them have about 78 myomeres before the vent, and this seems to have been the only reason for Gopinath regarding them as distinct from L. scheelei. However, they are all relatively large leptocephali and in this respect agree with Weber's specimen. They are probably undergoing metamorphosis. The single specimen, 90mm in length, described and figured by Deraniyagala (L. Ariosoma scheelei I regard Deraniyagala's larva as belonging to this species.
Ancona (L. Ariosoma anago, from the Red Sea, which I regard as L. Ariosoma scheelei. Ancona's specimens have 112–117 myomeres (compared with the 149–159 of A. anago), the pigmentation is typical of L. Ariosoma scheelei in all stages of development and the vent is essentiallv subterminal.
Ancona examined a small (195mm) juvenile of "A. anago", but the radiograph showed only 119 vertebrae. Norman (Ariosoma nigrimanus as so far the only known species of the genus from the Gulf of Aden. Norman does not give a vertebral count but in view of its area of capture A. nigrimanus is a possible adult of Ancona's leptocephali and juvenile.
Leptocephalus dentatus (Garman, L. obtusus (Garman, Ariosoma gilberti (Ogilby, Thyreoconger hemiaspidus Wade, A. gilberti. This gives a range of vertebrae for the latter as ca. 116–121, close to the range shown above for L. Ariosoma scheelei. Comparison of Norman's description and figure for A. nigrimanus and Wade's for Thyreoconger hemiaspidus (A. nigrimanus is the adult of Ancona's leptocephali and juvenile, the latter provide a vertebral count which would suggest that A. gilberti may be a synonym of A. scheelei.
Growth and Metamorphosis: The 67 specimens of L. Ariosoma scheelei range in length from 15.1mm to 154.8mm of which the majority are larvae at various stages of growth short of metamorphosis but three (96.7mm, 106.0mm and 119.4mm) are undergoing metamorphosis.
Number of Preanal Myomeres.—During active growth from 15mm to about 40mm the vent moves from about myomere 60 to myomere 105 in the total of about 115. The position of the vent then remains constant during further increase in total length. At 120mm to 130mm metamorphosis begins.
Number of Dorsal and Anal Fin-rays.—These can first be counted when the larva is only 40mm in length at which time they number about 50 in the anal and 60 in the dorsal. The origin of the dorsal fin is never appreciably in advance of the level of the vent in larvae prior to metamorphosis (even in individuals of 130mm), usually only about two myomeres in front of it, so that extremely rapid movement of the dorsal origin to its final position over the pectoral, must occur during metamorphosis.
Teeth.—Although some specimens of L. Ariosoma scheelei (including the one described above) show little differentiation in size and grouping of teeth, most have teeth which are very similar to those of Gnathophis (see Castle, Gnathophis, as growth proceeds the bases of the larval teeth become overgrown by the fleshy snout and they appear to be relatively shorter in late leptocephali.
Pigmentation.—At 15mm the loptocephalus of Ariosoma scheelei has two minute, compact spots on each myoseptum below the midlateral line along the whole of the body except on the tip of the caudal region; dorsal pigment is restricted to about four large stellate spots along the dorsal midline; about four similar spots equally spaced along the midventral bodywall; a few compact spots on the dorsal aspect of the tip of the spinal cord. At about 30mm total length there are about 4–5 spots on. each myoseptum, about 18–20 dorsal spots, about 12 ventral spots and pigment on the tip of the caudal region. At the time when the posterior movement of the vent ceases (40mm) the dorsal spots become more compact, the caudal pigment is lost and the ventral stellate chromatophores are replaced by the small, somatic spots in a row on the ventral midline before the gall bladder and the two rows of minute, compact spots on the dorsal aspect of the intestine. Spots on the bases of the dorsal and anal rays begin to form at about 50mm total length.
Geographical Range and Location of Spawning Areas (Text-fig. 2, A)
Except for the two metamorphosing specimens of L. Ariosoma scheelei beachcast at Sydney and a single, nearly full-grown larva collected off Rottnest Island, Western Australia, all of the present material, that is, 64 specimens, came from the area included by the Solomons, New Hebrides and New Caledonia. The leptocephali are rare and the adult, if present, may be very rare in the Australian region. Small specimens of from 15mm to 35mm were collected in the area immediately surrounding New Caledonia and New Hebrides in 20–120 metres. Larger specimens are more widely distributed. It is therefore probable that spawning of Ariosoma scheelei in the southwest Pacific occurs in the waters around New Caledonia. In consideration of the size of specimens previously recorded from the Banda and Sulu Seas and neighbouring areas by previous authors it is likely that larvae move from the New Caledonia region westwards through the Malayan Archipelago as well as occasionally to Western and Eastern Australia. Ancona's studies of this species shows that it must also spawn in the Red Sea since his smallest specimen was 15.5mm total length; Gopinath's 216 larvae from southern India are all very large and it is unlikely that the species spawns in this area; these larvae are probably derived from the Red Sea.
Should A. gilberti from the Pacific central America finally prove to be a synonym of A. scheelei, the geographical range of the latter will extend across the whole of the Indo-Pacific. Briggs (Albula vulpes and Chanos chanos, have an extended pelagic larval life.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (19 specimens): 43.7mm total length, IFO Station D15b, 9° 50′ S, 159° 20′ E, Alepisaurus ferox; 145.1, St LL 57–6–3, 22° 50′ S, 165° 36′ E, Alepisaurus ferox; 151.2, St Ep7b, 18° 23′ S, 159° 47′ E, Alepisaurus ferox.
C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection (14 specimens): 11.8, 16.0, 16.8, Warreen Station 32/38, 24° 29.5′ S, 153° 26.5′ E, Warreen St 30/48, 32° 03′ S, 113° 30′ E,
Australian Museum Collection (1 specimen): 102.1, Aust. Mus. regd. No. IA.3815, Dana Station 3663, haul 9, Tasman Sea, 33° 33′ S, 154° 04′ E,
Western Australian Museum Collection (47 specimens): 11.1, Accession No. P5229, Lancelin, 16 miles west of West End, Rottnest Island, Western Australia, Umitaka Maru, 13° 45′ N, 115° 12′ E, Lancelin, 43mls,
Description: 81 specimens: total lengths 11.1mm–278.0mm, myomeres 134–153, maximum number of dorsal fin-rays observed 120, anal 111. Description made from a half-grown specimen, Western Australian Museum Ace. No. P5553 (measurements in mm): total length 87.3, head 3.6, snout 1.5, eye 0.8, cleft of mouth 1.9, postorbital 1.5, pectoral 0.8,
Body conspicuously elongate, much compressed except along head, maximum depth contained about 10 times in total length, tapering equally in front of, and behind, the midpoint of body. Head very short, about 24 in total, with the throat indented; snout conical, about 2.5 in head, its dorsal profile slightly concave; nasal organ large, close in front of eye, its dorsal margin with a ventral extension midway along its length indicating approaching separation of the nares; eye small, 4.5 in head, round; cleft of mouth oblique, reaching to below middle of pupil; teeth rather broad-based, acute; anterior grasping tooth on the extreme tip of snout followed by a series of four large teeth and then by another series of seven smaller teeth; those on lower jaw similar. Pectoral fin short, about 2.0 in postorbital, delicate, rounded; dorsal and anal fin very short, restricted to posterior tip of body, dorsal origin close to level of vent, caudal with well-developed hypurals and fin-rays.
Pigmentation in preservative as follows:—below the midlateral level on each myoseptum from the seventh to the last an oblique line of minute, compact, elongate, somatic chromatophores, each arranged anteroposteriorly; these pigment spots are few in number anteriorly and are more numerous (usually about 12 in specimens of about 100mm total length but up to 20 in larvae of about 180mm) in the middle of the body length but decrease again in number until posterior to the level of the vent they number about four on each myoseptum; from about segment 20 to level of vent an unpaired series of small, diffuse, somatic chromatophores, 1–2 to each segment, on the dorsal midline; from the pectoral region to about halfway along the body length an unpaired series of small, diffuse, somatic chromatophores, about 5–6 to each segment, on the ventral midline, this series becoming less regular and fading out beyond the midpoint; posterior to the gall bladder a paired series of small, compact, splanchnic chromatophores above the intestine, about 6–9 per segment, through to the vent, although these are much less regular along the posterior part of the intestine; a few scattered chromatophores on the dorsal and anal bases; chorioid pigment present.
Remarks: The specimens described above have the larval pigmentation, round eye, short dorsal and anal fins and subterminal vent established for leptocephali of the genus Ariosoma. They agree well with Leptocephalus mauritianus Pappenheim, Ariosoma howensis (McCulloch and Waite, L. Ariosoma Mauritianum.
Geographical Range and Location of the Spawning Areas (Text-fig. 3, A).
The present leptocephalus is now known from the Solomons, through New Caledonia and as far south as Sydney, but also occurs abundantly on the west Australian coast; a few specimens have been recorded from Mauritius and the Red Sea. Smallest specimens were taken off Sydney and Rottnest Island, Western Australia and suggest that spawning takes place in these areas. The leptocephali of this species collected in the neighbourhood of the western spawning area during Ariosoma mauritianum is therefore at least one year but is probably not much more than this, especially since most of the larger larvae appear to be close to metamorphosis.
The species is not so abundant as L. Ariosoma scheelei in the New Caledonia area and the smallest specimen from this region is 43.7mm in total length suggesting that spawning probably does not occur here. Ancona (L. Ariosoma mauritianum from the Red Sea, and together with the Mauritius examples, a third spawning area, off east Africa, is suggested.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (32 specimens): 60.7mm total length, IFO Station D5, 18° 32′ S, 159° 50′ E, Katswonus pelamis; 279.1, 289.5, St LL 57–3–8, 22° 35′ S, 166° 08′ E, Alepisaurus ferox; 314.0, St G 23, 22° 07′ S, 165° 04′ E, Makaira audax; two specimens in poor condition, St G LL 10, 20° 55′ S, 163° 18′ E, Alepisaurus ferox.
Western Australian Museum Collection (1 specimen): 167.9, Accession No. P5241, Lancelin, 45 miles west of West End, Rottnest Island, Western Australia,
Description: 33 specimens, total lengths 60.7mm–314rnm, myomeres 157–172, maximum dorsal rays 108, anal rays 91. Description made from an almost full-grown specimen, IFO Station S.11 (measurements in mm): total length 188.5, head 5.0, snout 1.8, eye 1.2, cleft of mouth 2.3, postorbital 2.3, pectoral 0.8, snout-vent 184.3, predorsal 185.0, depth just before eye 2.3, at pectoral origin 4.3, at midpoint between pectoral and vent 12.4, at vent 2.9. Dorsal rays 64, anal rays 53, caudal rays 3 + 3. Teeth Myomeres 150 + 10 = 160. 1st vertical blood vessel at myomere 11, last at 81. Anterior margin of gall bladder at myomere 27.
Body extremely elongate but not filamentous, much compressed, except along head, maximum depth about 16 times in total, tapering equally in front of, and behind midpoint of body. Head extremely short, about 38 in total length, indented at the throat; snout conical, 2.8 in head, its dorsal profile straight; nasal organ large, close in front of eye, nares distinct; eye small, about four times in head, round; cleft of mouth oblique, extending to below middle of pupil; teeth broad-based, relatively powerful; an anterior grasping tooth on the anterior tip of snout followed by four large teeth and six much smaller teeth; those on lower jaw similar in size and distribution. Pectoral fin short, about 2.5 in postorbital or equal to horizontal diameter of eye; dorsal and anal fins very short, restricted to posterior tip of body, dorsal origin very close to level of vent, caudal with well-developed hypurals and fin-rays.
Pigmentation in preservative as follows:—below midlateral line on each myoseptum from about the tenth segment to the tail tip an oblique line of minute, compact, elongate, somatic chromatophores, each arranged anteroposteriorly; these pigment spots are few in number anteriorly but increase to about 15–20 (in full-grown specimens of 250mm) in the middle of the body length and finally decrease to about four or five on each myoseptum posterior to the level of the vent; a series of small, diffuse, somatic chromatophores on the dorsal midline from the 15th segment to the level of the vent, 1–2 per segment but more widely spaced posteriorly; a series of small, diffuse, somatic chromatophores along the ventral midline from the pectoral region to about the midpoint of the body length, about six per segment, the series fading out gradually towards the midpoint; posterior to the gall bladder a paired series of small, compact, splanchnic chromatophores along the dorsal aspect of the intestine to the vent, about 9–10 per segment but much less frequent posteriorly; a spot on the bases of most dorsal and anal rays; chorioid pigment present.
Remarks: In the 45 specimens of Ariosoma anago examined by Asano (Ariosoma in the Indo-Pacific I hesitate to separate these leptocephali from A. anago on the basis of this difference.
Only one relatively small specimen, measuring 60.7mm total length, is present in the above collection while the others are all over 90mm and reach 300mm, a very large size for congrid leptocephali. In all specimens the vent is very close to the tip of the caudal region indicating that there are no metamorphosing larvae in the collection. However, some show well-developed fin-rays and ossification of the skull, etc., indicating that they are probably full-grown.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (2 specimens): ca. 58mm total length (damaged), IFO Station G LL 13, 23° 31′ S, 165° 53′ E, Alepisaurus ferox; 76.3, St S.7, 10° 48′ S, 159° 00′ E,
Description: Made from the undamaged specimen (measurements in mm): standard length 75.3, head 4.1, snout 1.6, eye 1.1, cleft of mouth 2.4, postorbital 1.8, pectoral 1.2, snout-vent 73.0, predorsal 74.9, depth just before eye 1.8, at pectoral origin 3.1, at midpoint between pectoral and vent 8.6, at vent 2.5. Pectoral rays undeveloped, only a few dorsal and anal rays present at tip of caudal region, caudal rays 5 + 3. Teeth Myomeres 127 + 11 = 138. Last vertical blood vessel at myomere 68. Anterior margin of gall bladder at myomere 21.
Body moderately elongate, much compressed except along head, deep, the maximum depth about 8.0 in total, reducing very rapidly at the head but more gradually along the posterior third of the body. Head short, about 18 in total, distinct from trunk; snout acute, about 2.5 in head, its dorsal profile concave; nasal organ poorly developed, placed close in front of eye; eye circular, 2.0 in snout or 5.5 in head; cleft of mouth slightly oblique, extending to below middle of pupil; teeth relatively acute and distributed as follows: a minute tooth on the anterodorsal tip of snout followed by a large grasping tooth, a series of four large teeth and eight much smaller teeth, those of lower jaw similar. Pectoral fin short, less than length of snout, delicate, subcircular in shape; dorsal and anal fins very short with only their basal structures developed, the dorsal origin slightly behind level of vent.
Pigmentation in formalin as follows:—a short, oblique line of minute, compact, somatic chromatophores on each myoseptum below the lateral line, the maximum number of spots in these lines being about six in the middle of the body; a paired row of regular, essentially segmental, somatic chromatophores on the ventral surface from the level of the pectoral to the gall bladder; a paired row of compact, splanchnic chromatophores in the order of eight per segment arranged along the kidney ducts above the intestine to the vent; numerous small, somatic spots scattered over the whole of the lateral surface, more numerous below the lateral line; scattered spots on the dorsal and anal bases and over the base of the caudal fin; pigment in the chorioid.
Vertical blood vessels to the viscera numerous, beginning at the tenth myomere and occurring every three or four segments to the 68th.
Remarks: The leptocephali described here show similarities to Ariosoma leptocephali in the round eye, the posterior position of the vent, the short dorsal and anal fins and the presence of the rows of small chromatophores on the myosepta below the lateral line. The scattered lateral chromatophores, however, suggest that this leptocephalus does not belong in Ariosoma, but nevertheless, it clearly belongs in the Anagoinae-group of congrid leptocephali. Only one other genus. of this group is present in the Indo-West-Pacific and this is Alloconger Jordan and Hubbs, with its two species Alloconger anagoides (Bleeker, A. shiranago Asano, A. shiranago, A. s. shiranago Asano, A. s. major Asano, A. anagoides, known from Indo-Malaya to Japan, has about 143. In view of the geographical distribution of the latter species I am satisfied that if the leptocephalus described-above is an Alloconger then it is probably referable to A. anagoides. The relatively large size of the two larvae (ca. 58mm and 76.3mm) suggest that the spawning area for the species may be distant from the area of capture.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (2 specimens): type, 108.8mm total length, IFO Station S.6, 1.1° 51′ S, 159° 13′ E,
Description: Made from the type specimen, IFO St S.6 (measurements in mm): standard length 107.7, head 5.0, snout 2.2, eye 1.2, cleft of mouth 3.1, postorbital 2.0, pectoral 0.9, snout-vent 102.5, predorsal 103.1, depth just before eye 2.4, at pectoral origin 5.4, at midpoint between pectoral and vent 15.0, at vent 3.8. Pectoral rays undeveloped, only a few dorsal and anal rays present at tip of caudal region, caudal rays 4 + 3. Teeth Myomeres 130 + 17 = 147 (133 + 18 = 151 in the paratype). Last vertical blood vessel at myomere 92. Anterior margin of gall bladder at myomere 20.
Body moderately elongate, much compressed except along head, deep, the depth about 6.5 in total length, reducing very rapidly at the head but more gradually along the posterior half of the body to tip of caudal region. Head short, about 21 in total, not conspicuously distinct from trunk; snout acute, 2.3 in head, its dorsal profile slightly concave; nasal organ close in front of eye, with distinct nares; eye circular, contained twice in snout or four times in head; cleft of mouth slightly oblique, extending to below middle of pupil; teeth robust, not excessively acute, the smaller ones curved forward a little at their tips, distributed as follows:—one large anterior grasping tooth followed by six large teeth and 10 much smaller ones, the pattern similar in the lower jaw. Pectoral fin short, about half the length of snout, rounded, delicate; dorsal fin originating about 20 segments in advance of level of vent, anal fin very short.
Pigmentation in formalin as follows:—an oblique line of minute, compact, somatic elongate chromatophores on each myoseptum below the lateral line, reaching 20–24 in number at the midpoint of the body, briefly separated from a row of similar spots above the angle of each myoseptum below the lateral line (see text-fig 5, H) reaching a maximum of about 12 spots; a row of up to 12 similar spots above the angle of each myoseptum above the lateral line (text-fig. 5, G); irregularly scattered ventral, somatic chromatophores in the order of four per segment before the level of the gall bladder; a row of minute, compact, splanchnic chromatophores on each kidney duct above the intestine; a few diffuse chromatophores along the dorsal midline; scattered pigment on the bases of the terminal dorsal and anal rays and over the base of the caudal fin; halfway along the midlateral line an oval patch of numerous, minute, somatic chromatophores but this only occurs in the larger specimen and its presence may be abnormal; chorioid pigment present.
Vertical blood vessels to the viscera very numerous, beginning at the 5th myomere and occurring every two or three myomeres to the 92nd myomere. Gall bladder spherical. End of intestine with about 10mm trailing free from the body wall. (L. scalarum = ladder, in reference to the ladder-like pattern of the rows of pigment spots).
Remarks: The present species conforms well in possessing a round eye, short dorsal and anal fins, a posterior vent and rows of chromatophores on the myosepta below the lateral line with Anagoinae-type leptocephali. It has no scattered lateral chromatophores as in the larva previously referred to Alloconger anagoides and has the last vertical blood vessel at the level of myomere 92, compared with myomere 68 in L. ?Alloconger anagoides. In addition, the new species has additional lines of minute chromatophores in two places on each myoseptum. As far as I am able to determine from the literature there is no known species of Leptocephalus which has this remarkable pattern of lateral pigment. L. scalaris is therefore unique amongst congrid leptocephali. Ancona (L. macrenteron which has the posterior part of the intestine free from the body (as in the present species) but without the additional pigment on the myosepta. I believe this pigment to be abnormal in both species and that L. macrenteron is referable to L. Ariosoma mauritianum.
This group of larvae in the present collection includes seven genera and ten species. Three of these species belong to Conger, one other possibly to Scalanago Whitley, Conger found in New Zealand waters are described together with a brief account of their leptocephali.
Two earlier accounts (Castle, Gnathophis Kaup and two which I have referred to Pseudoxenomystax Breder. There are in this region two further congrids which are much more common, referable to Conger Oken, C. wilsoni (Bloch and Schneider, C. verreauxi Kaup, Conger. Although Kanazawa (C. wilsoni and C. verreauxi but among the congrid leptocephali in the present collection there are a number of larvae of C. wilsoni and C. verreauxi and these are also described here.
C. wilsoni is a relatively slender eel, seldom reaching more than C. oceanicus (Mitchell, C. philippinus Kanazawa, C. wilsoni is also similar to C. verreauxi, the second species known from New Zealand, but the latter is a much more robust eel, reaching 2,000mm in length, having 157–165 vertebrae, 40–44 lateral line pores before the level of the vent, dorsal fin-rays 331–347, branchiostegal rays 10–11, a small eye 1.2–1.9 per cent of total length, the dorsal fin originating about level with the pectoral tip and teeth on each jaw 35–67; it has an essentially southern distribution in New Zealand from Cook Strait southwards but is taken northwards to the Bay of Islands and along the southeast coast of Australia.
Material Examined: 25 specimens, 69.6mm–627.5mm total lengths; Urupukapuka Island, Bay of Islands; rotenone; Leptocephalus monganius Phillipps,
Description: Proportional measurements (in per cent of total length) and counts from 30 specimens: total lengths 69.6mm–815mm, standard 97.4–99.1, head 12.5–16.3, snout 3.2–4.5, eye 1.9–3.9, interorbital 2.1–3.6, upper jaw 4.5–6.4, postorbital 7.7–9.8, branchial aperture 1.1–2.3, branchial interspace 2.1–4.2, pectoral 3.4–5.5, preanal 35.2–40.8, predorsal 19.1–21.9, depth before eye 2.9–5.0, at pectoral origin 4.2–6.9, at vent 4.0–6.0, at midpoint of caudal region 3.1–5.2. Branchiostegal rays 8–9, pectoral rays 16–18, dorsal rays before level of vent 57–65, dorsal rays 294–330, anal rays 229–261, caudal rays 4–5 + 4–5, lateral line pores before level of vent 36–41, vertebrae 141–149.
A slender eel which seldom grows to more than 1,000mm, rounded to oval in section, with the vent always well in front of the midpoint of the body. The head is markedly depressed, especially in smaller specimens, the lips are thick and the eye is large. The dorsal begins distinctly behind the level of the pectoral tip. Olive blue-black above, white, tinged with yellow below, the dorsal and anal fins white with a conspicuous but narrow black margin and the eye with a brilliant silver-green patch above the pupil.
Head sharply conical, conspicuously depressed, in most specimens the jaw muscles bulging upwards so that the head is clearly differentiated from the trunk, short, about 7.5 in total length; snout rather blunt but flattened or depressed dorsally, about 4.0 in head,
Teeth relatively small, but a little larger anteriorly than posteriorly, most bluntly conical and villiform in smaller specimens, a few sharp and slightly recurved, those on the maxilla and dentary flattened anteroposteriorly with their bases much wider than their tips. Maxillary teeth about 45 in a specimen of 630mm total length, uniserial, forming a sharp cutting edge; a few minute teeth in a second longitudinal row medial to the main row about one-third of the way along the outer row. Premaxillary-ethmoid teeth about as large as those on the anterior extremity of the maxilla, about a dozen in number, forming a narrow, curved patch, about twice as broad as long, which barely shows in advance of the tip of the lower jaw when the mouth is closed. Vomerine teeth in an oval patch, about one-third the length of the maxillary row, much larger anteriorly than those more posteriorly placed and about 30 in number. Teeth on the dentary similar to those on the maxilla but with a few extra teeth in a short row in front as well as a short subsidiary row of about eight teeth medial to the main row.
Anterior nostril terminal, tubular, with the tube directed forwards. Posterior nostril small, oval, placed close to the anterior margin of eye and above the horizontal diameter, usually widely open. Eye subcircular, relatively large, contained more than four times in the postorbital. Fleshy interorbital about equal to eye. Branchial aperture lateral, about equal to eye, having a concave free edge, oblique, with the upper extremity above middle of pectoral base and well in advance of level of lower extremity. Vent not protruding conspicuously into the lateral profile.
Dorsal and anal fins delicate, not high and about equally developed. Dorsal originating about half to two-thirds of the pectoral behind level of pectoral tip. Anal fin not as high as dorsal. Caudal fin continuous with dorsal and anal tips, not abbreviated, pointed. Pectoral elongate-oval in shape, with a rounded posterior margin, originating at about the midlateral level, its base oblique and the fin directed slightly posterodorsally, about equal to cleft of mouth in length.
Lateral line moderately conspicuous but barely raised above lateral surface, arising high on head and reaching midlateral level just posterior to level of vent. Pores simple, minute and visible almost to tail tip. Cephalic sensory pores consisting of one occipital pore; one pore on the upper lip at the level of the anterior margin of eye; a large pore immediately behind and level with corner of mouth; two pores set closely together in a short groove on the anterodorsal tip of snout; one pore in front of, and one behind, base of anterior nostril tube; a minute pore on ventral surface of snout; eight mandibular pores in a curved line from the operculum to the tip of lower jaw. Surface sensory organs on the head indicated in most specimens by a transverse row of minute papillae across nape and a semicircular row in front of pectoral base. Most lateral line pores with minute papillae anterodorsal to them.
Colour in life olive blue-black over the dorsal surface and to a point halfway between lateral line and ventral midline, mostly creamish-white below, sometimes tinged with yellow. Head often with a patch of silver posterior to eye. Iris blue-purple anteriorly and posteriorly with a brilliant crescentic patch of silver green above but this fades rapidly on death. Dorsal and anal fins white with a complete, narrow black margin.
Remarks: The most recent account of Conger wilsoni is that of Kanazawa (C. wilsoni does not deepen in the body greatly during growth as does C. verreauxi and remains a slender eel with a cylindrical body very little compressed along the caudal region. C. wilsoni has much more numerous teeth on the maxilla and dentary than does C. verreauxi. At 257mm total length, C. wilsoni has teeth 45/46 on each half of the upper and lower jaw respectively, while at 815mm it has 66/69. This increase with growth is shown graphically in text-fig. 7. Other differences between C. wilsoni and C. verreauxi have already been indicated.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (14 specimens): 25.2mm total length, IFO Station D10b, 14° 13′ S, 157° 55′ E,
Western Australian Museum Collection (1 specimen): 90.3, Accession No. P5167, 47 miles west of West End, Rottnest Island, Western Australia,
New Zealand Collections (2 specimens): 85.0, Dom. Mus. No. 2942, Bay of Islands, from flank of isolated reef rising from 50 metres on a sandy bottom, March, Chrysophrys auratus(Forster).
Description: 17 specimens: total lengths 25.2mm–l00.0mm, myomeres 141–151, dorsal rays 286–317, anal rays 190–261, last vertical blood vessel at myomere 52–56. Description made from a specimen which has almost reached metamorphosis, IFO St S.4 (measurements in mm): total length 74.0, head 4.8, snout 1.4, eye 1.2, cleft of mouth 2.3, postorbital 2.5, pectoral 1.1, snout-vent 64.9, predorsal 45.9, depth before eye 1.4, at pectoral origin 3.0, at midpoint between pectoral and vent 7.0, at vent 4.5. Branchiostegal rays 8, pectoral rays not yet formed, dorsal rays before level of vent 244, dorsal rays 317, anal rays 227, caudal rays 5 + 4. Teeth Myomeres 116 + 26 = 142. a–d = 46. Last vertical blood vessel at myomere 54.
Body moderately elongate, much compressed except along head, not deep, the maximum depth about nine times in total length, reducing more gradually in front of the midpoint. Head short, about 14 in total, relatively distinct from trunk; snout blunt, about 3.5 in head, its dorsal profile convex; anterior nostril tube directed forwards, posterior nostril with a simple raised rim and placed above horizontal diameter of eye; eye oval, the greatest diameter vertical, but the horizontal diameter 1.3 in snout; cleft of mouth slightly oblique, extending to below posterior margin of pupil; teeth very acute, barely curved; branchial aperture curved, its ventral margin not yet attached to the lateral surface. Pectoral fin short, about equal to length of snout, almost circular in shape with the fin-rays not developed; dorsal fin low, originating at myomere 70, fin-rays very numerous and closely packed; anal fin similar; caudal pointed.
Pigmentation in formalin consisting of a conspicuous brown to black crescentic patch below the posteroventral margin of the iris; a rounded chromatophore deep in the throat; a paired, ventral, somatic series of about 70 rounded chromatophores following the course of the intestine from the 10th myomere, thence on each segment to the vent; this series continues as scattered chromatophores on the bodywall above the anal fin; a series of minute, irregularly shaped chromatophores on the bases of most of the anal rays; a few on the bases of the dorsal terminal rays; a scattering of minute pigment spots over the base of the caudal fin; chorioid pigment present.
Vertical blood vessels to the viscera numerous, occurring irregularly every four or five segments from about myomere 12 to myomere 54 although this last vessel is the only one that is conspicuous. Gall bladder usually difficult to distinguish.
Remarks: Leptocephali of C. wilsoni are strikingly similar to those of Gnathophis incognitus Castle (C. wilsoni, however, as in other species of Conger, this ventral series continues above the anal fin almost to the tip of the caudal region. This is a characteristic feature which distinguishes Conger leptocephali although very small specimens of about 20mm do not usually have this series developed and consequently may be confused with those of Gnathophis.
It may be suggested that the above collection of C. wilsoni leptocephali contains a number of larvae which could be referred to Conger cinereus cinereus(Rüppell, C. cinereus cinereus have chromatophores along the midlateral line (Ancona, C. cinereus cinereus, that is, two cephalic pores behind the eye and the sixth suborbital pore above the level of the corner of the mouth (see text-fig. 9, D). Relevant data for this specimen are as follows:—C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection: 85.7mm total length, Fairwind collection, Kieta, Bougainville Island, Solomon Islands,
Growth and Metamorphosis
Growth of the leptocephalus of C. wilsoni proceeds much as in Gnathophis, the main difference being the gradual development of a very blunt snout, thick, fleshy lips which are characteristic of the adult, the tube of the anterior nostril becomes directed forwards and not downwards and the anal fin lengthens so that the pigment spots above it increase in number; in Gnathophis there are none of these spots behind the vent.
Geographical Distribution and Location of the Spawning Areas
There are insufficient larvae in the present collection to indicate a precise spawning area but the larvae are clearly smallest north of New Caledonia. One specimen collected in Western Australia at 90.3mm has reached metamorphosis, while a single glass-eel and the largest larva in the collection were taken off northern New Zealand. The absence of very small larvae in collections from these areas suggests that C. wilsoni spawns well to the north of its area of adult distribution.
Material Examined: One specimen, 261.0mm total length; Bay of Plenty; stomach of groper, Polyprion oxygeneios (Bl. and Schn.), caught in 180 fathoms; Dom. Mus. No. 2032. One specimen, 329.1mm; Pegasus Bay, trawl; Ikatere;
Description: Proportional measurements (in per cent of total length) and counts from the above 14 specimens: total lengths 261.0mm–1597mm, standard length 98.6–99.6, head 13.1–16.1, snout 3.0–4.5, eye 1.2–1.9, interorbital 1.5–3.5, upper jaw 4.2–5.8, postorbital 7.6–10.3, branchial aperture 1.2–2.5, branchial interspace 2.1–6.4, pectoral 4.6–6.3, preanal 36.4–43.5, predorsal 17.2–21.8, depth before eye 2.7–4.9, at pectoral origin 3.8–8.1, at vent 3.6–8.6, at midpoint of caudal region 2.7–5.5. Branchiostegal rays 10–11, pectoral rays 17–18, dorsal rays before level of vent 56–70, dorsal rays 331–347, anal rays 238–265, caudal rays 5 + 4, lateral line pores before level of vent 40–44, vertibrae 157–165.
Body massive in most specimens but distinctly slender in small examples of less than about 600mm; usually growing to about 1500mm but occasionally reaching 2000mm. In
Head bluntly conical, depressed, not conspicuously differentiated from trunk, short, about 7.0 in total length; snout blunt, flattened dorsally, about 4.0 in head, not projecting in advance of tip of lower jaw; the latter rounded in ventral view, strong, shovel-like; mouth terminal, slightly oblique with cleft extending to below posterior margin of pupil and contained 3.0 times in head; upper lip very well developed, especially along its anterior half, beginning a little behind tip of snout and weaker posteriorly; lower lip thicker, overlapping lower jaw, beginning a little behind tip of lower jaw; tongue strong, pointed, extending to a point halfway between levels of anterior and posterior nostrils.
Teeth relatively small but robust, generally larger anteriorly than those more posteriorly placed; most of them bluntly conical and villiform in small specimens, but a few on premaxillary-ethmoid and anterior part of vomer sharp and recurved, the main teeth on the maxilla and dentary flattened anteroposteriorly with wide bases. Maxillary teeth about 48 in a specimen of 1150mm total length, uniserial, forming a sharp, powerful cutting edge; a row of about 24 minute teeth forming a second longitudinal row medial to this main row; a small triangular patch of about 18 teeth outside the most anterior part of the maxillary row. Premaxillary-ethmoid teeth mostly large, about 20, forming a curved patch, twice as broad as long, which barely shows in advance of lower jaw when mouth is closed; the most anterior teeth of this patch minute. Vomerine teeth large anteriorly but much smaller posteriorly, about 30 in number, forming a tear-shaped patch, less than one-third the length of the maxillary patch with the broad end anterior. Teeth on the dentary essentially in two longitudinal rows of which the lateral row contains about 50 teeth, similar to those on the maxilla; those of the medial row are minute but about the same in number; a few teeth are placed outside the main row in a short row of about five teeth at the anterior tip of the dentary.
Anterior nostril terminal, tubular, with the tube directed forwards and equal in length to about half the pupil. Posterior nostril small, placed close to anterior margin of eye and above the horizontal diameter, usually widely open, oval. Eye oval, small, about 5.5 in postorbital. Fleshy interorbital broad, about twice diameter of eye. Branchial aperture lateral, 1.5 times eye, widely open, with a concave free edge and slightly oblique, its upper extremity near middle of pectoral base. Vent protruding a little into the lateral profile.
Dorsal and anal fins delicate in small specimens but thick and fleshy in large individuals, the dorsal somewhat higher than the anal. Dorsal originating less than the diameter of the pupil behind the level of the pectoral tip, reaching its greatest height in the last quarter of the caudal region where it equals the depth of the body at that point. Anal similar to the dorsal. Caudal fin continuous with the tips of the dorsal and anal fins and pointed. Pectoral fan-like, thick, fleshy and deep in larger specimens, about equal to length of cleft of mouth, its base oblique.
Lateral line ridge inconspicuous, arising high on the head and curving down to meet the midlateral level well behind level of vent. The pores are simple, minute and visible almost to caudal tip. Cephalic sensory pores as in C. wilsoni, that is, an occipital pore, five pores on tip of snout and around base of anterior nostril, two pores on maxilla, one behind corner of mouth, three on opercular region and six on lower jaw. Specimens of about 600mm or less may show a pattern of minute surface sensory papillae across the dorsal surface of the head, in front of the pectoral base and around the nostrils.
Colour in life generally dark grey or brown to blue-black above, light grey to white below on the abdomen but specimens may sometimes be mottled grey and white. Small specimens have a narrow black margin to the dorsal and anal fins. Iris dull silver.
Remarks: The specimens of C. verreauxi examined above conform well with Kanazawa's redescription (Conger ?labiata from Sydney. There was possibly some confusion
Conger. The "belly and fins of a bright yellow" would be an unusual colouration for either C. verreauxi or C. wilsoni, both of which are known from south-east Australia; the type of C. labiata therefore may well belong to some other genus of eels, perhaps Ophichthus.
Proportional Changes During Growth: In C. verreauxi, after reaching about 500mm, there is a marked increase in the depth of the body along the trunk so that specimens of about 1500mm may be extremely large in girth. There is at the same time a very great increase in weight and large C. verreauxi may be 351b–401b. Related to this, the branchial interspace increases much more rapidly than any other proportion of the body. The branchial aperture also lengthens very rapidly. The largest specimen of C. verreauxi examined (1597mm) is about six times the length of the smallest specimen (261mm) and comparing the two specimens, the increases in the various proportions are as follows:—head 6.8, snout 7.7, eye 4.6, interorbital 8.5, upper jaw 8.1, postorbital 7.3, branchial aperture 11.3, branchial interspace 11.2, pectoral 7.0, preanal 6.8, predorsal 7.3. The eye therefore decreases in size relative to the length of the body as growth proceeds while the head and preanal length increase at about the same rate relative to the length of the body.
A conspicuous change during growth in both C. verreauxi and C. wilsoni is an increase in number of the compressed teeth along the maxilla and dentary (for comparative data see Kanazawa, C. verreauxi has 35/36 teeth on the maxilla and dentary respectively. The numbers increase regularly with growth and reach a maximum of about 63/65 at 1200mm total length. This increase is illustrated in text-fig. 7. and compared with the numbers of compressed teeth in C. wilsoni. The difference in number of teeth on the maxilla or dentary provides a valuable character for the separation of the two species although at lengths up to 200mm there is insufficient difference in the numbers to distinguish examples of the two species on this character alone.
Food: C. verreauxi feeds on a great variety of marine animals including fish, Crustacea and cephalopods. The stomach of a specimen taken at Big Bay, South Westland, contained two scarlet parrot-fish, Pseudolabrus miles (B1. and Schn.), a part of a blue-cod, Parapercis colias (Forster), part of a crayfish, Jasus lalandii and two octopus tentacles. On the west coast of the South Island and around Wellington C. verreauxi is known to enter crayfish pots to feed on captured crayfish, as well as to attack crayfish in rocky crevices.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (5 specimens): 24.1mm total length, IFO Station S.5, 13° 30′ S, 162° 00′ E,
C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection (1 specimen): 107.5, Warreen Station 105/39, 41° 17′ S, 148° 26′ E,
Description: Six specimens: total lengths 24.1mm–139.Cmm, myomeres 160–165, dorsal rays 286–317, anal rays 190–261, last vertical blood vessl at myomere 52–56. anterior margin of gall bladder at about myomere 55. Description made from the Warreen Station 105/39 specimen (measurements in mm): total length 107.5, head 6.6, snout 2.0, eye 1.4, cleft of mouth 3.0, postorbital 3.6, pectoral 2.0, snout-vent 85.5, predorsal 58.3, depth just before eye 3.0, at pectoral origin 4.0, at midpoint between pectoial and vent 8.0,
Body moderately elongate, much compressed except along head, shallow, its maximum depth near level of vent about 13 in total length, reducing much more rapidly behind vent. Head short, about 16 in total, relatively distinct from trunk; snout very blunt, short, 3.3 in head, its dorsal profile convex; nostrils separated, the anterior one a short tube directed forwards and with a complete rim, the posterior one with a simple raised rim and placed just in front of eye; eye oval, its greatest diameter vertical, but the horizontal diameter 1.4 in snout; cleft of mouth slightly oblique, extending to below posterior margin of pupil; teeth very acute, in three series in the upper jaw and in the lower. Pectoral short, equal to snout in length; dorsal fin relatively well-developed with clearly observable fin-rays; anal similar; caudal with well-developed hypurals and rays.
Pigmentation in formalin as follows:—a small crescentic patch of brownish pigment above the iris and a larger, more conspicuous crescentic patch below the pupil; two small, somatic chromatophores behind the branchial aperture; a paired, ventral, somatic series of rounded chromatophores following the course of the intestine from the 8th segment to the vent, at intervals of one or two segments; this series continues above the base of the anal fin as a rather widely spaced series along the caudal region; a stellate chromatophore on the base of every third or fourth anal ray; a scattering of chromatophores over the base of the caudal fin; chorioid pigment present.
Vertical blood vessels to the viscera numerous, beginning at about the 5th myomere with a barely visible vessel, then continuing irregularly to the 54th myomere.
Remarks: The leptocephali described above are typical of Conger larvae in having a paired, ventral, somatic series of chromatophores along the level of the intestine to the vent, a crescentic patch of pigment on the oval eye and a series of chromatophores above the anal fin. They agree well in number of myomeres, 160–165, with C. verreauxi which is the only species of Conger with more than 160 vertebrae. The hypurals are elongated and similar in shape to those of the adult, although in the specimen described the caudal rays differ slightly in number from the number normally observed in the adult. Leptocephali of C. verreauxi differ essentially from those of C. wilsoni in having a greater number of myomeres, in conformity with the difference in myomeres of the adults, i.e. 160–165 in C. verreauxi compared with 141–151 in C. wilsoni. Larvae of C. verreauxi reach a greater length when full-grown than do those of C. wilsoni (140mm compared with 100mm). Spawning of C. verreauxi probably takes place well to the north of New Caledonia on the evidence of the distribution and size of the leptocephali although this is a remarkably great distance from the geographical limits of the essentially southern C. verreauxi.
Material Examined: Western Australian Museum Collection (13 specimens): 20.9mm total length, Accession No. P5298, Lancelin, 34 miles west of West End, Rottnest Island, Western Australia,
C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection (3 specimens): 48.2, Warreen Station 37/48, 28° 48′ S, 113° 36′ E,
Description: 16 specimens: total lengths 20.9mm–60.2mm, myomeres 112–119, dorsal rays 121–149, anal rays 198–240, a–d = 35–37, last vertical blood vessel at myomere 52–56, anterior margin of gall bladder at myomere 16–18. Description made from the largest specimen which is probably full-grown, Warreen Station 36/48 (measurements in mm): standard length 59.3, head 4.2, snout 1.9, eye 0.9, cleft of mouth 2.3, postorbital 2.1, pectoral 1.6, snout-vent 45.8, predorsal 24.1, depth before eye 1.9, at pectoral origin 3.2, at midpoint between pectoral and vent 7.8, at vent 7.4. Dorsal rays 233, dorsal rays before level of vent 148, anal rays 144, caudal rays 4 + 3. Teeth Myomeres 76 + 38 = 114. a–d = 36. Last vertical blood vessel at myomere 54, anterior margin of gall bladder at myomere 18.
Body moderately elongate, compressed, deep, the maximum depth 7.0 in total, reducing evenly in front of, and behind, midpoint of body. Head relatively long, 12.0 in total, not greatly differentiated from trunk; snout acute, about 3.0 in head, its dorsal profile slightly convex; both nostrils well separated, the anterior nostril carried on the end of a short tube; eye oval, 2.0 in snout; cleft of mouth slightly oblique, extending to below posterior margin of pupil; teeth moderately acute. Pectoral long, a little longer than snout, elongate-oval; dorsal and anal fins well-developed with clearly defined fin-rays, the dorsal origin well in advance of the level of the vent; caudal relatively pointed.
Pigmentation in formalin or alcohol consisting of a paired, regular, ventral series of rounded, somatic chromatophores following the course of the gut from the pectoral every two or three segments to the vent; a crescentic patch of pigment below the iris; rather more widely spaced chromatophores along the base of the dorsal than the more closely set series on the anal base, with a scattering of pigment on the caudal base; a midlateral series of large, constantly dendritic chromatophores (none rounded in any specimen seen) from the pectoral to the tip of the caudal region, spaced at every two or three segments anterior to the level of the vent but more widely spaced posteriorly, each chromatophore with many fine, thread-like branches radiating from a compact centre.
Remarks: The leptocephalus described above agrees in the arrangement of pigmentation and general morphology with L. congroides Ancona, Scalanago lateralis Whitley, Scalanago lateralis agree so well that I am satisfied the larvae are identifiable with this species. The leptocephalus has a restricted distribution since it is known only from collections made in Western Australia and this agrees well with the distribution of the adult. The number of relatively small larvae in the collection indicates spawning in Western Australian waters.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (6 specimens): type, 72.9mm total length, IFO Station S lm 6, 10 miles west of Bulari Pass, New Caledonia, Alepisaurus ferox.
Description: Six specimens: total lengths 46.1mm–75.9mm, myomeres 104–111, dorsal rays 133–174, anal rays 92–139, a–d = 13–14, last vertical blood vessel at myomere 34–40, anterior margin of gall bladder at myomere 22–24. Description made from the type, an almost full-grown specimen IFO Station S lm 6 (measurements in mm): standard length 72.2, head 5.9, snout 2.0, eye 1.0, cleft of mouth 2.3, postorbital 3.0, pectoral 1.3, snout
Body elongate-oval, much compressed, very deep, the maximum depth 4.1 in total, reducing equally in front of, and behind, the midpoint of the body. Head relatively long, about 12.0 in total, clearly differentiated from trunk; snout bluntish, 3.5 in head, its dorsal profile convex; anterior nostril tubular and directed forwards, well separated from the posterior nostril which is placed just in front of eye; eye oval, 2.0 in snout; cleft of mouth slightly oblique and reaching below middle of pupil; teeth moderately acute. Pectoral oval, equal to snout; dorsal and anal fins well-developed, especially posteriorly; caudal rounded.
Pigmentation consisting of a paired, ventral series of about 12 somatic chromatophores from the level of the pectoral to the level of the last vertical blood vessel which is placed halfway along gut; a line of five spots on the throat; a crescentic patch of pigment below the iris; a few spots on the bases of some anal rays. (L. laureus = relating to the laurel, in reference to the laurel-leaf shape of the body.)
Remarks: The ventral series of pigment spots and the crescentic patch of pigment below the eye suggests that this leptocephalus belongs with the Congrinae, but I cannot further identify the species. Considering that the larvae of the shallow water genera Gnathophis and Conger are known and that the myomeres are very low in number for a congrid eel, precluding the identification of the species with such long-tailed forms with elongated hypurals as Uroconger and Promyllantor, I can suggest only that L. laureus may belong to an unknown deep-water congrid. The number of myomeres is lower than that recorded for any known congrid eel.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (8 specimens): 23.3mm total length, 47.3, 66.8 (type), 76.0, IFO Station S.5, 13° 30′ S, 162° 05′ E,
Description: Eight specimens: total lengths 23.3mm–76.0mm, myomeres 134–152, dorsal rays 167–185, anal rays usually poorly developed, a–d = 43–46, last vertical blood vessel at myomere 47–51, anterior margin of gall bladder at myomere 26–28. Description made from the type, a 66.8mm specimen, IFO Station S.5 (measurements in mm): standard length 65.5, head 4.6, snout 2.0, eye 0.8, cleft of mouth 2.7, postorbital 2.4, pectoral 1.0, snout-vent 63.0, predorsal 50.4, depth before eye 1.6, at pectoral origin 3.1, at midpoint between pectoral and vent 8.6, at vent 2.8. Dorsal rays 175, dorsal rays before level of vent 148, only terminal anal rays developed, caudal rays 4 + 3. Teeth Myomeres 130 + 12 = 142. a–d = 45. Last vertical blood vessel at myomere 49, anterior margin of gall bladder at myomere 28.
Body elongate, but not excessively so, compressed, deep, the maximum depth about 7.0 in total length. Head relatively long, about 13.0 in total, distinct from trunk; snout acute, long, 2.5 in head, its dorsal profile slightly concave, never convex; nostrils set closely together immediately in front of eye; eye oval, its horizontal diameter 2.5 in snout; cleft of mouth slightly oblique, relatively long, reaching to below posterior margin of eyeball; teeth acute. Pectoral oval, 1.5 in snout; dorsal weakly developed; anal fin very short; caudal rounded.
Pigmentation in the form of a paired, ventral series of up to 70 compact, somatic chromatophores from below the pectoral origin every segment (anteriorly) or every 3–4 segments (posteriorly) to the vent; a line of five spots on the throat; a crescentic patch of pigment below the iris and a minute patch above the eyeball; scattered spots on the bases of the anal rays and over the base of the caudal. (Gk. stenos = narrow, rhynchos = snout,
Remarks: The most characteristic feature of this species is the elongate, acute in reference to the narrow, beak-like snout.) snout which is not found in other congrid leptocephali. The ventral series of chromatophores and crescentic patch below the eye shows that this species belongs
Uroconger, Promyllantor and other similar genera.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (2 specimens): type, 44.0mm total length, IFO Station 7–6, 22° 35′ S, 166° 16′ E, Alepisaurus ferox.
C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection (2 specimens): 21.9, Warreen Station 26/40, 32° 34′ S, 152° 55′ E,
Description: Four specimens: total lengths 21.9mm–122.6mm, myomeres 186–199, last vertical blood vessel at myomere 57–59. Description made from the type, a 44.0mm specimen, IFO Station 7–6 (measurements in mm): standard length 43.8, head 2.9, snout 1.0, eye 0.7, cleft of mouth 1.1, postorbital 1.1, pectoral 1.2, snout-vent 42.1, predorsal 33.5, depth before eye 1.6, at pectoral 2.1, at midpoint between pectoral and vent 4.1, at vent 0.7. Fin-rays not developed. Teeth Myomeres 163 + 36 = 199. Last vertical blood vessel at myomere 59.
Body elongate, compressed, depth 10.0 in total. Head relatively long, 14.0 in total, not conspicuously differentiated from trunk: snout short, 3.5 in head, its dorsal profile slightly convex; nostrils not yet differentiated but the olfactory organ set in the middle of snout; eye oval, 2.0 in postorbital or 1.3 in snout; cleft of mouth oblique, reaching to below middle of pupil, teeth acute. Pectoral fin round to oval, 1.5 in snout, median fins inconspicuous.
Pigmentation consisting of a paired ventral series of rather diffuse somatic chromatophores from the pectoral region to the vent; about three pigment spots on the throat; a minute patch of pigment above the eyeball and a crescentic patch below it; a regular series of large, diffuse chromatophores following the midlateral level from the pectoral to the tip of the caudal region, spaced at about every two to three segments; an irregular line of diffuse chromatophores above and below this midlateral line; a scattering of larger chromatophores on the caudal tip. (L. tres = three, linea = a line, in reference to the three lines of chromato phores on the lateral surface.)
Remarks: This larva is immediately distinguishable from all other congrid leptocephali in having three longitudinal lateral rows of chromatophores. It also has a high number of myomeres for congrid larvae as well as a narrow caudal (although the three specimens described are clearly not full-grown) which would probably possess elongated, narrow hypurals. This suggests that the adult would be a long-tailed congrid but further identification is at present not possible.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (5 specimens): type, 40.9mm total length, IFO Station D1b, 20° 56′ S, 163° 46′ E, Alepisaurus ferox; 64.9, St S lm B, 10 miles west of Bulari Pass, New Caledonia,
C.S.I.R.O. Division of Fisheries and Oceanography (Cronulla) Collection (1 specimen): 29.2, Warreen Station 16/38, 33° 40′ 20″ S, 151° 27′ 30″ E, 2/.9/38, N200H, 25m, 30mins.
Description: Six specimens: 29.0mm–115.3mm total lengths, myomeres 160–174, last vertical blood vessel at myomere 49–56, anterior margin of gall bladder at myomere 35–36. Description from the type, a 40.9mm specimen, IFO Station Dlb (measurements in mm): head 3.3, snout 1.4, eye 0.8, cleft of mouth 1.6, postorbital 1.6, pectoral 1.2, snout-vent 39.8, predorsal ca. 29.3, depth before eye 1.9, at pectoral origin 2.3, at midpoint between pectoral and vent 5.3, at vent 1.1. Dorsal rays 224, other rays not developed. Teeth Myomeres ca. 136 + 31 = ca. 167. a–d = ca. 48. Last vertical blood vessel at myomere 52. Anterior margin of gall bladder at myomere 35.
Body moderately elongate, much compressed, a little deeper behind the midpoint where the depth is 7.7 in total length and from here tapering gradually towards snout, more rapidly towards caudal tip, the latter turned downwards; vent subterminal in this specimen; pigmentation mainly as a paired series of chromatophores along the level of intestine and three longitudinal rows of chromatophores on the lateral surface.
Head short, 12 in total, not clearly differentiated from trunk; snout short, 2.4 in head, its dorsal profile concave, the nasal organ conspicuous but the nostrils as yet undeveloped; eye oval, 1.6 in snout; cleft of mouth oblique, extending to below middle of pupil. Teeth acute but generally short; the first on each jaw a forwardly-directed needle-like fang, that of the upper jaw placed on anterodorsal aspect of snout; the second of upper jaw very small, less acute, flatly triangular in section with the apex lateral; the third tooth much larger but similar in shape to the second; the remaining eight teeth similar, small, gradually increasing in size towards angle of mouth; those of the lower jaw decreasing slightly in size from the second to the last but generally larger than those of upper jaw. Pectoral a large, fleshy flap, 1.5 times longer than eye; dorsal fin with faint but nevertheless countable basal structures, originating well in advance of vent.
Pigmentation as follows:—a narrow, crescentic patch of pigment above iris and a larger, more conspicuous but also more diffuse patch below iris; three round, compact chromatophores in a line on the lateral aspect of throat; a paired, ventral series of rather diffuse, rounded, somatic chromatophores from below pectoral base along level of intestine as far as vent, a little fewer than one per segment; a series of more diffuse somatic chromatophores slightly below middle angle of myomeres from the 5th segment to the tip of caudal region, spaced at about one chromatophore per 2–4 segments (but rather irregularly spaced); a second longitudinal, lateral series of diffuse, somatic chromatophores between this midlateral row and the dorsal flexure of the myomeres, much more infrequently placed than those of the midlateral row; a similar but still more infrequently spaced row of chromatophores along the ventral flexure of the myomeres; pigment in the chorioid. (L. geminus = a twin, in reference to the close similarity of this species to Leptocephalus trilineatus.)
Remarks: The group of specimens described here is clearly very similar to the previous species in pigmentation, that is, in the possession of three longitudinal rows of chromatophores on the lateral surface of the body. Other pigmentation is typical of the larvae of various congrid eels (the ventral series along the level of the intestine and the presence of iris pigment). The present specimens, however, have fewer myomeres (160–174) than the previous species and the last vertical blood vessel is placed a little further forwards (at myomere 49–56 compared with myomere 59 in the previous species). I am satisfied that these specimens represent a distinct species, especially in view of similar distinctions between the leptocephali of say, Ariosoma scheelei and A. mauritianum. There are two species to which L. geminus may possibly be referred, if only on the basis of myomere counts and the structure of the caudal. These are Pseudoxenomystax bulbiceps (Whitley, P. hirsutus Castle, L. geminus. Dorsal rays in these two species are between 300 and 350 in number, an appreciably higher number than in the largest specimen of L. geminus. However, in this specimen the dorsal rays are poorly developed and would clearly be more numerous in the metamorphosed eel. In a single, very large specimen of L. geminus from the northeast Indian Ocean which I have examined, the dorsal fin-rays have reached their full number (indicated by the abrupt origin of the dorsal fin) of about 260 but unfortunately in
L. geminus to be the young of one of the above species of Pseudoxenomystax. If this were the case then a second species of this genus, as represented by L. trilineatus with more numerous myomeres is also suggested.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection (3 specimens): type, 73.0mm total length, IFO Station 57–4–3, 20° 50′ S, 166° 50′ E, Alepisaurus ferox.
Description: From the type, a 73.0mm specimen (measurements in mm): standard length 72.7, head 4.1, snout 1.2, eye 0.9, cleft of mouth 1.9, postorbital 2.0, pectoral 1.0, snout-vent 70.2, predorsal 27.1, depth before eye 1.9, at pectoral origin 3.2, at midpoint between pectoral and vent 8.2, at vent 1.6. Fin-rays not developed. Teeth Myomeres 189 + 54 = 239. a–d = 142. Last vertical blood vessel at myomere 62. Anterior margin of gall bladder at myomere 60.
Body relatively elongate, much compressed, its maximum depth 8.9 in total length; vent subterminal in this specimen; pigmentation inconspicuous, restricted mainly to a line of small, somatic chromatophores on the midlateral line and another along the level of the intestine from the pectoral to the vent.
Head short, about 18 in total, not conspicuously differentiated from trunk; snout blunt, 3.4 in head, its dorsal profile convex and the nasal organ well developed; eye oval, 1.3 in snout; cleft of mouth oblique, reaching to below middle of pupil; teeth moderately acute, conspicuous. Pectoral round, relatively short, about equal to eye; dorsal origin well in advance of level of vent at the level of the 47th myomere; rays of dorsal and anal fins not well enough developed to be counted but probably about 300; caudal fin weak with the hypurals and rays undifferentiated.
Pigmentation consisting of a curved, narrow patch above iris and a larger, more readily noticeable crescentic patch below iris on its posteroventral corner; a line of five, small, compact spots on the lateral wall of the throat, lateral to the heart; a paired ventral series of small, somatic chromatophores spaced at about one per segment at the level of the intestine from the 6th myomere to the vent (although these spots are much less frequent near the vent); a midlateral series of small, diffuse or compact, somatic chromatophores, about one per segment, from the 8th segment to about the level of vent; three minute spots slightly in advance of the caudal tip; chorioid pigment present. (L. medius = the middle, punctum, = a point, in reference to the longitudinal row of chromatophores along the middle of the body.)
Remarks: The present species bears close resemblances to the leptocephali of Conger conger (L.) and C. cinereus Rüppell in having a midlateral line of chromatophores, one per segment, as well as an intestinal series and a patch of pigment below the iris (these last two also being typical characters of members of the Congrinae). However, the number of myomeres in the present species is much greater than in any known species of Conger (the highest being that found in C. verreauxi Kaup, 165–172). I find only one species of Leptocephalus which approaches the present material in number of myomeres, pigmentation and other characters; this is L. magnaghii Ancona, L. magnaghii is great enough to indicate a second species. With regard to the identity of the adult of L. mediopunctatus, only one congrid eel is recorded to have more than 200 vertebrae; this is Uroconger lepturus (Richardson,
vertebrae and an almost filamentous tail with narrow hypurals. It could therefore be suggested that L. magnaghii Ancona is referable to U. lepturus since the former has 209–219 myomeres and rather narrow hypurals indicating that the caudal tip in the adult would probably be attenuated. Should this identification prove correct then a second species of Uroconger, to which L. mediopunctatus may be referred, is probably present in the Indo-Pacific. However, whether or not these suggestions may be confirmed must await examination of Uroconger for vertebral counts on a worldwide basis.
Material Examined: Centre d'Océanographie de l'Institut Français d'Océanie Collection {10 specimens): 13.6mm total length, IFO Station D5, 18° 32′ S, 159° 50′ E,
Description: 10 specimens: total lengths 13.6mm–61.1mm, myomeres 110–122, dorsal rays (2 specimens) 331 and 346, anal rays (2 specimens) 286 and 236, caudal rays (2 specimens) 5 + 3 and 4 + 3, a–d = 23–28, last vertical blood vessel at myomere 42–48, anterior margin of gall bladder at myomere 7–10. Description made from an almost fullgrown specimen, IFO Station S.4 (measurements in mm): total length 48.8, standard 47.8, head 3.9, snout 1.3, eye 0.6, cleft of mouth 1.8, postorbital 2.1, pectoral 1.5, snout-vent 19.2, predorsal 7.9, depth before eye 1.4, at pectoral origin 3.1, at vent 12.2, at midpoint of caudal region 9.7. Fin-rays as in the second specimen above, dorsal rays before level of vent 107. Teeth Myomeres 41 + 71 = 112. a–d = 27. Last vertical blood vessel at myomere 46. Anterior margin of gall bladder at myomere 10.
Body elongate-oval, much compressed except along head, deep, the maximum depth about four times in total length, tapering about evenly in front of, and behind midpoint. Head relatively long, about 12.5 in total, clearly differentiated from trunk; snout moderately blunt, 3.0 in head, its dorsal profile barely convex; both nostrils well separated on a conspicuous nasal organ; eye oval, twice in snout; cleft of mouth extending to below middle of pupil, slightly oblique; teeth moderately acute. Pectoral oval, a little longer than snout; dorsal origin well in advance of level of vent; anal long; caudal with well developed broad hypurals and fin-rays.
Pigmentation in formalin as follows:—a small, compact chromatophore at the base of each tooth of the anterior group of seven teeth on the maxilla and the posterior nine on the dentary; six compact chromatophores on temporal region; three postorbital spots; two oblique preopercular rows of eight and five chromatophores respectively; 10 in a group in front of pectoral base; five spots in a row on the lateral aspect of the throat, this row merging into a paired, ventral, somatic series of about two minute chromatophores per segment; this series bifurcates at the level of the gall bladder to form two rows of minute spots, one a somatic series of about one spot per segment to the vent, the other a splanchnic series above intestine of about three spots per segment; a conspicuous row of compact or diffuse spots slightly in advance of each myoseptum, as well as on the lateral body wall above and below the muscle segments; a row of chromatophores on the anal base; a few spots on the base of the posterior portion of the dorsal; scattered spots over the surface of the caudal; a small, crescentic patch of pigment below the posteroventral corner of the iris; a minute patch above the anterodorsal corner of the iris; pigment in the chorioid.
Remarks: The ten specimens of the distinctive leptocephalus described above show remarkably close resemblances to the single specimen of L. hyoproroides described by Strömman (L. hyoproroides. Schmidt (L. hyoproroides and states that a leptocephalid (58mm total length) collected from Thor Station 156 in the Mediterranean can be referred to the same species and identifies L. hyoproroides as the young of Chlopsis bicollaris Rafinesque (Nettastomidae). Although both Ancona (C. bicollaris, following Schmidt, they are clearly in error, since larvae of the latter species have 130–140 vertebrae and the lateral pigment restricted to a midlateral row. Despite resemblances in the distribution of pigment along the level of the intestine, the structure of the hypurals and the anterior position of the vent, I believe the presence of the patches of pigment above and below the iris in the present specimens from New Caledonia to be a sufficiently reliable character by which to refer L. hyoproroides to the Congridae and not to the Nettastomidae. L. hyoproroides has large pectoral fins while the young and adults of Chlopsis bicollaris lack pectorals. Although Schmidt believes this to be no barrier to the identification of L. hyoproroides with the Nettastomidae since pectorals may be lost during larval development, in those eels in which the adults lack pectorals (muraenids, various ophichthids) young larvae always have much reduced pectorals but these are lost long before the leptocephalus is full-grown. In having splanchnic pigment above the intestine L. hyoproroides shows some resemblance to members of the Anagoinae.
The 15 species of eel larvae described in this paper, together with the two further species described in an earlier account (Castle, Orsom III, the oceanographic vessel of the Centre d'Océanographie de l'Institut Français d'Océanie, Nouméa); (b) a long and relatively narrow area from southern Queensland to Tasmania off the east Australian coast over the continental shelf and slope (collections mainly from Warreen, the oceanographic vessel then attached to the C.S.I.R.O., Division of Fisheries and Oceanography, Cronulla, New South Wales; (c) a smaller area west of Rottnest Island, off Perth, Western Australia (collections made during the period mid–Lancelin, the research vessel used by the Western Australian Museum, Perth). A few other leptocephali came from the New Zealand area, mainly as beachcast specimens.
The present collection of over 500 congrid larvae is part of an even larger assembly of about 1,100 leptocephali which also includes larvae of other families of eels. Although this is by far the most extensive collection of eel larvae yet recorded from the whole of the Indo-Pacific smaller collections have nevertheless been examined. The most important of these (500 specimens) is recorded by Ancona (Dana collection from this area was large but the congrids in the collection have not been examined. Other notable collections have been made from the Indo-Malayan archipelago (Strömman,
In the initial sorting of the present collection of eel larvae the leptocephali described in this paper were separated from all other groups of larvae in having a pectoral fin at all stages of development, a caudal fin which is not reduced in length in full-grown specimens, the gut is not festooned or swollen at any point and pigment always occurs as a regular, ventral series of chromatophores. The myomeres are never extremely numerous, that is, they are never more than 250 and the body is never filamentous. This combination of characters is not found in other groups of leptocephali.
Many eel larvae with this combination of characters have been described and a few of these have been referred to the family Congridae on the basis of transitional, metamorphosing specimens which show characters of both the larva and the young congrid eel (e.g. Conger conger, Ariosoma balearica and Gnathophis habenatus). Indeed, the characters which identify leptocephali to the familial level are now in general well established so that there are no serious difficulties in the broad sorting of collections of eel larvae.
Within the family Congridae leptocephali fall quite readily into two major divisions. The first of these, subfamily Anagoinae Asano, L. Ariosoma balearica (De Laroche) from the Central Atlantic and the Mediterranean. Five species described in the present paper are referred to the Anagoinae. The second division, subfamily Congrinae, has leptocephali which possess an oval eye with iris pigment, a paired series of somatic chromatophores along the ventral midline from the pectoral region to the vent or not as far, and the vent usually appreciably in advance of caudal tip. Typical representatives of this group are L. Conger conger (L.) and L. Gnathophis habenatus (Richardson).
Although one species in the present collection, L. hyoproroides Strömman, Scalanago Whitley, Scalanago (type species, S. lateralis Whitley, Scalanago to the Congrinae (which replaces the Leptocephalinae because of Direction 87 of the International Commission on Zoological Nomenclature, Conger Oken,
Below the subfamily level the leptocephali described above show clear distinctions mainly in body shape and pigmentation. Further subdivisions are based on such numerical characters as the number of myomeres, the relative position of the gall
Conger and Gnathophis). I therefore propose that the subdivisions of the congrid leptocephali described here, which are based mainly on amount and distribution of chromatophores, actually represent generic divisions. This agrees with my findings in the examination of larvae of other families of eels in the present collection. A disturbing feature of eels in general is that the limits of many genera of adults within a particular family have not always been clearly defined, due to the essential monotony of external characters. Generic differences as suggested above in the leptocephali may well contribute to the resolution of such confusion wherever it should arise.
Including the two species of Gnathophis already described (Castle, Ariosoma-group and the Bathycongrus- complex of Ogilby has scarcely been critically examined. As a contrast, the congrid eels of the Japanese region have been carefully studied in detail by Asano (
The congrid larvae in the collection range in size from about 5mm to about 300mm (although the majority are between 25mm and 200mm in length) and include a small number which are in stages of metamorphosis. The length of a full-grown congrid leptocephalus depends mainly on the species to which it belongs but in general those of the Anagoinae are much longer (reaching more than 300mm in Ariosoma anago) and deeper than those of the Congrinae (which reach 140mm in Conger verreauxi) but are more often less than 100mm. However, in at least one species (Gnathophis habenatus) evidence was previously given (Castle,
Most collections in the three areas suggest that leptocephali of any particular species may remain for some time in the vicinity of the spawning area so that it is only the presence of very small larvae which can be taken as a reliable indication of the location of the spawning area. Small larvae of the various species indicate that there are two broad areas in the southwest Pacific in which spawning of these congrid eels may take place. The more northerly one lies between New Caledonia and the Solomon Islands over a depth of between 3,000m and 5,000m; the other lies off the New South Wales coast at about the latitude of Sydney over similar depths. At least Gnathophis habenatus, G. incognitus Castle, Ariosoma mauritianum spawn in the latter area but the majority of the remainder probably spawn north of New Caledonia. The third spawning area indicated by the present collection is off Rottnest Island, Western Australia, again over relatively great depths of 3,000m–5,000m where spawning of A. mauritianum and Scalanago lateralis takes place. Spawning in most cases appears to occur in relatively shallow depths of about 50m–100m and dispersal of the young larvae does not clearly follow the prevailing surface currents. In one species at least (Gnathophis
habenatus) the larvae are found northwards to the New Caledonia region, a dispersal movement contrary to the south-flowing East Australian Current.
Most of the larvae were collected with plankton nets of up to 200cm in diameter in horizontal and oblique hauls, a larval fish net or by 3ft or 5ft Isaacs-Kidd midwater trawls. These latter nets proved to be admirable for collecting larger leptocephali. A few specimens from the New Caledonia region were found in the stomachs of skipjack, yellowfin tuna and lancet fish (Katsuwonus pelamis (L.), Neothunnus macropterus (Temm. and Schleg.), and Alepisaurus ferox Lowe, respectively) taken on troll lines and longlines in the off-shore waters of New Caledonia.