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Congrid Leptocephali in Australasian Waters with Descriptions of Conger wilsoni (Bl. and Schn.) and C. verreauxi Kaup.
L. ?Alloconger anagoides (Bleeker, 1864), Text-fig. 5, A-D
L. ?Alloconger anagoides (Bleeker, 1864), Text-fig. 5, A-D
| 1864. | Ophisoma anagoides Bleeker, Atlas ich. Indes. Orient. Neerl., 4: 27, p1. 149, fig. 3. |
| For further synonymy see Asano, 1962, p. 76. | |
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, 4/4/62, stomach of lancet fish, Alepisaurus ferox; 76.3, St S.7, 10° 48′ S, 159° 00′ E, 12/6/62, MWT5, H, ca. 95m.
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 .gif)
Myomeres 127 + 11 = 138. Last vertical blood vessel at myomere 68. Anterior margin of gall bladder at myomere 21.
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Text-fig. 5.—Figs. A-D, L. ?Alloconger anagoides bleeker, 1864), 76.3mm total length, IFO Station S.7: Fig. A, lateral view; Fig. B, lateral view of head; Fig. C, lateral view at about myomere 50 to show lateral pigment and splanchnic chromatophores on the kidney ducts; Fig. D, tip of caudal region. Figs. E-I, Leptocephalus scalaris n. sp., type, 108.8mm total length, IFO Station S.6: Fig. E, laterial view; Fig. F, lateral view of head; Fig. G, lateral View at about myomere 53 to show pigment below lateral line, and Fig. H, above lateral line; Fig. I, tip of caudal region.
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, 1864) and A. shiranago Asano, 1958. The two subspecies of A. shiranago, A. s. shiranago Asano, 1958, and A. s. major Asano, 1958, both of which are known only from Japan, have 144–147 and 156–161 vertebrae respectively while 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.