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Studies on Thalassinid Crustacea (Decapoda, Macrura Reptantia) with a Description of a New Jaxea from New Zealand and an Account of its Larval Development

1. Description of Jaxea novaezealandiae n.sp. with Notes on Distribution and Habits

1. Description of Jaxea novaezealandiae n.sp. with Notes on Distribution and Habits

Adults of the New Zealand Jaxea have been elusive. The first significant record was of a large ovigerous female taken alive in a deep dredge haul from soft muddy ground at 11 fathoms in Wellington Harbour (New Zealand Oceanographic Institute, NZOI Stn. A355, 23 July 1957). This survived in an aquarium for several days, but died without any of the eggs hatching. The second record was also obtained by the New Zealand Oceanographic Institute when an associated pair was taken alive in an orange peel grab from about 8 fathoms in Port Underwood, Marlborough, on the south-western side of Cook Strait (NZOI Stn. C228, 15 September 1959). These also survived for several days but did not attempt to burrow or to take food while under observation in an aquarium.

During 1964-65, R.G.W. was able to obtain live adult specimens at night using a small otter trawl in about 2 to 10 fathoms in Evans Bay, Wellington Harbour. Specimens were taken in July, August and November, 1964, and during 1965. page 5 They were trawled from a bottom of soft putrid mud, apparently living in association with the stomatopod Squilla armata (H. Milne Edwards) and an abundant spatangoid urchin, Echinocardium cordatum (Pennant). Specimens of Jaxea taken by this method were kept alive for up to 11 days in the Victoria University Marine Laboratory at Island Bay, Wellington. None appeared to take food or to burrow successfully during these periods.

Adult Jaxea are now known in New Zealand waters from Hawke Bay on the east coast of the North Island in the north, to the Marlborough coast of Cook Strait in the south. All records have been from protected inshore waters in depths ranging from about 2 to 12 fathoms on muddy or sandy bottoms.

Fragments of unknown reptants taken from fish stomach contents in the Wellington Harbour and Cook Strait areas during the period 1954-59 can now be identified as the New Zealand Jaxea. These records, coupled with the abundance of trachelifer larvae of Jaxea in the Wellington plankton (Wear, 1965), give an indication of the true status of this species in the Wellington area where substrate conditions appear to suit the apparently restricted habitat preference of J. novaezealandiae.

Larvae attributed to the New Zealand Jaxea were first taken from the Bay of Islands, northern New Zealand, by the British Antarctic "Terra Nova" Expedition in 1910 (Gurney, 1924). Larvae have also been examined (R.G.W.) from the Hauraki Gulf and Auckland Harbour, Wellington Harbour, off Kaikoura and off Banks Peninsula (east coast of the South Island). From this it would appear that the species may be widespread in the New Zealand area on suitable ground and at suitable depths.

Adult Material Examined

Hawke Bay: NZOI Stn. B2, off Mohaka, 39° 08′ S., 177° 13′ 30″ E., 25/8/1956, cone dredge on muddy with fine sand bottom at 18 metres (1 damaged specimen, 5.5mm).

Wellington Harbour: From dogfish stomach, off Petone Beach, 16/11/1954 (female carapace length 11mm). Victoria University Zoology Department Collections VUZ 32, off Petone Beach, 41° 14′ 30″ S., 174° 52′ 6″ E., 16/1/1956, dredge on mud bottom at 8 fathoms (associated pair, male 8mm, female 7.5mm); VUZ 68, between Somes Island and Days Bay, 41° 16′ 12″ S., 174° 52′ 51″ E., 16/5/1956, Petersen grab on mud bottom at 11 fathoms (associated pair, ? male 6mm, female 6mm). NZOI Stn. A 355, between Somes Island and Kaiwharawhara, 41° 15.6′ S., 174° 50′ E., 23/7/1957, Knudsen sampler dredge on mud bottom at 11½ fathoms (ovigerous female 18mm). From dogfish stomach (Mustelus lenticulatus) 6/7/1964, taken in otter trawl from 3 fathoms off Petone Beach (3 males 13mm, 13mm and 16mm). Shelly Bay, Evans Bay (R. G. Wear study area) numerous specimens taken by otter trawl from mud bottom in 2 to 10 fathoms, 1964-65, including the following: male 9mm, 6/7/1964; male 11mm (figured specimen) 11/7/1964; male 15mm (holotype), male 13mm, female 13mm, 3/8/1964; 2 males 9mm and 13mm, female 15mm, 26/8/1964; 1 male 10mm, 6/11/1964; 3 males 11mm, 11mm and 13mm, 1/6/1965.

Cook Strait: NZOI Stn. C 228, Port Underwood, Marlborough, 41° 19′ S., 174° 10′ E., 15/9/1959, orange peel grab on sandy mud at about 8 fathoms (associated pair, male 11mm, female 15mm).

Type Material

The holotype is the male from Shelly Bay, 3/8/1964, with carapace length of 15mm; the paratype upon which figs. 1 and 2 are mainly based is the male from the same area, 11/7/1964, with carapace length 11mm, though the figure of the page 6 mandible and certain other details are based on other specimens from Shelly Bay. All other material listed above, with the exception of the NZOI Stn. B 2 specimen is paratypic.

The holotype (Z. Cr. 1667), the figured paratype (Z. Cr. 1669) and the majority of the paratypes (8 specimens, Z. Cr. 1668, 1670-73) are in the Dominion Museum, Wellington; other paratypes are in the Victoria University of Wellington, Zoology Department (6 specimens), the New Zealand Oceanographic Institute, Wellington (3 specimens, 29, 30, 31), the Australian Museum, Sydney (2 specimens, P. 15164), and the Rijksmuseum van Natuurlijke Historie, Leiden (2 specimens, Crust. D. 22652–53). All measurements in the material examined list are of carapace length only (from posterior corner of orbit to level of dorsal midpoint of hind margin of carapace) and thus exclude the rostrum.

Illustrations

All drawings in this paper have been done by R.G.W.

Description of Jaxea novaezealandiae n.sp. (figs. 1 and 2)

A degenerate-eyed, relatively large, white, burrowing shrimp with elongated and enlarged chelipeds.

The carapace is laterally compressed and considerably shorter than the abdomen. The body and appendages are covered with a short and dense "pile" of fine, furlike setae, which gives the shrimp a soft, grey indistinct appearance. Fine, rust-like mineral grains, presumably from the substratum in which the animal burrows, are almost invariably enmeshed with the setal fur in the material examined and
Fig. 1.—Jaxea novaezealandiae n.sp., adult male, carapace length (excluding rostrum) 11mm, lateral view.

Fig. 1.—Jaxea novaezealandiae n.sp., adult male, carapace length (excluding rostrum) 11mm, lateral view.

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Fig. 2.—Jaxea novaezealandiae n.sp., adult. A, left mandible, median view; B, left 1st maxilla; C, left 2nd maxilla; D, left 1st maxilliped; E, left 2nd maxilliped; F, left 3rd maxilliped; G, 6th abdominal segment, uropods and telson, dorsal view; H, carapace and cephalic appendages, dorsal view. (All scale lines equal 1.00mm).

Fig. 2.—Jaxea novaezealandiae n.sp., adult. A, left mandible, median view; B, left 1st maxilla; C, left 2nd maxilla; D, left 1st maxilliped; E, left 2nd maxilliped; F, left 3rd maxilliped; G, 6th abdominal segment, uropods and telson, dorsal view; H, carapace and cephalic appendages, dorsal view. (All scale lines equal 1.00mm).

page 8 may superficially give the appearance of a pigmented exoskeleton. The cuticle is, however, firm, white, smooth and almost chalky rather than shiny. There is a very distinct linea thalassinica laterally on each side of carapace forming a hinged line upon which each pterygostomiobranchial portion of carapace can move. A distinct cervical groove is situated dorsally a little anterior to midpoint of carapace, exclusive of rostrum, but does not extend ventrally across linea. Anterodorsal surface of carapace smooth and produced anteriorly as a depressed, flattened, triangular rostrum, armed on each side of rounded tip with about 4 to 5, small, irregularly-placed teeth. Upper surface of rostrum with shallow, longitudinal depression extending a short distance onto carapace in midline. Anterolateral margin of carapace with a single small tooth immediately above origin of linea thalassinica and sometimes several minute "thorns" below. There is a short ?branchiostegal groove, directed posteroventrally, below level of antenna; remainder of anterolateral and ventrolateral border smooth and unarmed.

Abdomen of uniform depth throughout; pleuron of 1st segment triangular and overlapping anteriorly the convex posterolateral margin of carapace at level of linea. Pleura of other segments broadly rounded with weakly concave posterolateral margins, each overlapping posteriorly the next segment; ventral margins of 3rd to 6th pleura with minute serrations. Telson quadrate with distal edge weakly calcified and almost transparent; there is an indistinct, median, longitudinal groove dorsally flanked on each side by a row of about 6 to 7 small spines on a low, broad, longitudinal crest. Lateral margins are weakly and rather indistinctly serrated and posterior margin bears a row of long setae.

Eyes reduced and not extending laterally from beneath rostrum, not visible in dorsal view; cornea with black pigment in central portion only.

Antennules arise close together under rostrum, which extends to about midpoint of 2nd segment of peduncle. Second segment about half 1st and a little less than one-third of 3rd peduncle segment. Antennular flagellum a little longer than elongated 3rd segment. Exopod of about 23 segments longer and stouter than endopod of about 14 segments. Peduncle of antenna 5-segmented; proximal three and distal one short, 4th or penultimate segment greatly elongated, somewhat flattened, about 4 times length ultimate segment and about 5 times its own width in dorsal view. Scaphocerite greatly reduced and extending anteriorly from dorsodistal margin of 2nd peduncle segment; rounded in profile with about 1 to 3 irregular teeth anterolaterally. Antennal flagellum simple and about equal in length to carapace and abdomen excluding telson.

Mandible consists of molar process with curved serrated ridges and 3-segmented palp. First maxilla with two endites armed with stout bristles and setae medially, and a 2-segmented endopod with distal. segment shorter and more slender than proximal. Second maxilla with two endites each partially and unevenly divided into two, simple endopod and large scaphognathite with proximal lobe unusually long, tapering, truncate and bearing long whip of setae. All maxillipeds have large and prominent exopods, consisting of two parts, peduncle and flagellum, articulated at a distinct angle to one another; flagellum with single proximal segment at least half length of multi-segmented portion. First maxilliped with 2 incompletely separated endites; 2-segmented endopod with distal segment enlarged and rounded, and large triangular epipod. Second maxilliped with penultimate segment expanded as a rounded lateral lobe and with well developed podobranch and slender serrated epipod. Third maxilliped small and pediform, endopod of 5 segments with ischium bearing a prominent medial crest of about 12 to 14 sharp teeth; complex epipod consisting of small anterior lobe and bunch of long setae (setobranch), a podobranch and a posteriorly directed, serrate-margined mastigobranch. Two arthrobranchs are present on 2nd and 3rd maxillipeds, but only one on 1st.

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Chelipeds greatly developed, subequal in length and shape, and about equal in length to carapace and 1st to 3rd or 1st to 4th abdominal segments. Free finger slightly longer than fixed, both straight proximally and slightly curved together and acute distally (in large specimens finger tips tend to become blunt and rounded); free finger with two longitudinal angles rather than carinae along both inner and outer faces, fixed finger with one such longitudinal angle (indistinctly but evenly tuberculated or beaded) along both inner and outer faces. Both free and fixed fingers toothed; free with 3 broad, irregularly spaced teeth in proximal half and with distal half finely toothed; fixed with 1 to 4 broad teeth proximally, followed by one much larger, truncate tooth placed so as to interlock when closed between the two more distal of the broad proximal teeth of free finger; remainder of cutting margin of fixed finger with irregular series of differently sized teeth and often one enlarged tooth in distal third. Hand subequal in length to carapace including rostrum; hand length 3 to 4 times hand width; palm parallel-sided, rather than swollen, without ridges or tubercles, a little shorter than fingers. Carpus short, broad and unarmed. Merus long, a little shorter than fingers, enlarged distally so that distal width is nearly half length; unarmed dorsally but with row of 12 or more, sharp, slender teeth on narrow ventral margin. Ischium short and armed with row of 6 or more similar teeth ventrally as well as some sharp tubercles medially. Basis with single slender ventral tooth.

Second to 5th pereiopods short, compressed and, except for dactyls, rather similar in structure. Second pereiopod, unlike others, with fringe of setae along most of dorsal and ventral edges; dactyl flattened and blade-like, acute distally but otherwise unarmed, subequal to carpus and a little shorter than propodus; dactyl articulated to propodus so as to close with ventral edge against part of straight distal margin of latter and thus qualify as "subchelate"; propodus and other segments of this appendage unarmed, except for setal fringe; merus slender, width about 6 times length and length about 3 times that of propodus. Third and 4th pereiopods similar; both limbs with dactyl slender, triangular in section, curved distinctly laterally (out of plane of appendage), acute distally and armed ventrally with a curved, proximal, comb-like row of about 6 or more slender teeth; dactyl about 2/3 carpus; carpus a little shorter than propodus and a little less than half merus (a little more than half merus in 4th); all segments, except dactyl unarmed. Fifth pereiopod distinctly shorter than others; dactyl slender, acute, flattened but articulated in plane of propodus so as to close with part of its flat ventrally-oriented face against distal margin of propodus, both ventrolateral portion of distal margin of propodus and proximal portion of lateral edge of dactyl each armed with short row of slender teeth which meet and match when dactyl is closed against propodus in a "subchelate" manner; remainder of propodus and other segments unarmed; dactyl a little shorter than carpus, dactyl equal to half propodus, and propodus subequal to merus.

First pleopods absent in male; reduced, uniramous, slender and setose in female. Second to 5th pleopods in both sexes similar, well developed, biramous, with exopod and endopod in each subequal, lanceolate and setose. No appendix interna or appendix masculina present. Uropods with exopod subequal in length to telson and endopod a little longer; both endopod and exopod with transverse suture at about ¾ length of ramus and with row of short spines overlapping suture; one spine at outer edge of exopod suture row enlarged and extending posterolaterally; a few inconspicuous spines on lateral edge of both rami proximal to suture; each ramus with low, longitudinal ridge in midline.

Both male and female with 2 (occasionally 3) strong, anteriorly curved spines medially on coxa of 4th pereiopod; opening of vas deferens in male on raised tubercle medially on coxa of 5th pereiopod; oviduct opening in female medially on coxa of 3rd pereiopod. Eggs very small and numerous in the NZOI Stn. A 355 female. Both male and female have a broad, simple, rectangular plate on thoracic page 10 sternite between 4th pereiopods. This plate is oriented slightly posteriorly, concave in transverse section, with a longitudinal median groove which is deeper and more pronounced in the female.

Branchial Formula
Maxillipeds Pereiopods
1st 2nd 3rd 1st 2nd 3rd 4th 5th
Pleurobranchiae - - - - - - - -
Arthrobranchiae 1 2 2 2 2 2 2 -
Podobranchiae - 1 1 1 1 1 - -
Epipodites 1 1 1 1 1 1 1 -
Exopodites 1 1 1 - - - - -

This formula differs from that given by Selbie (1914) for J. nocturna in the presence of an arthrobranch but no podobranch on the 1st maxilliped, and two arthrobranchs instead of one on the 2nd maxilliped. Caroli (1924) critically re-examined the branchial formula of J. nocturna and gave a revised version which differs from that given above for J. novaezealandiae only in that there is no podobranch on the 3rd pereiopod. Thus both Selbie and Caroli record 17 gills in the European J. nocturna but differ in their rank and distribution. Our formula records 18 gills and agrees in complete detail with that given for the genus Jaxea (presumably based on J. nocturna) by Gurney (1942: 150). As reported below, a recent personal examination of J. nocturna gives 18 gills as formulated here for the New Zealand species.

The branchial formula given here for J. novaezealandiae also agrees in detail with the 18 gills recorded by Sakai (1962) for Laomedia astacina from Japan (disregarding the enigmatic "rudimentary" podobranch on the 1st maxilliped), and agrees with the formula we have for our undescribed eastern Australian Laomedia. In addition Naushonia crangonoides and N. portoricensis both have 18 gills (Chace, 1939: 528) and Thompson's formula for the former agrees with ours in distribution and rank; Chace's formula for the latter differs only in the status of gills on the 1st maxilliped and 4th pereiopod.

It would appear therefore that all known adult members of the family have 18 (or possibly 17) gills but there is no complete agreement on the distribution of these gills at either end of the series.

Systematic Position

Jaxea novaezealandiae is remarkably similar in general facies to the European J. nocturna, though it differs in many minor morphological features and in some body and appendage proportions. These differences are indicated in the key to the two species and can be studied in detail by comparing this description with the description and figures of Selbie (1914) for J. nocturna. The branchial formula and the ischial armature of the 3rd maxilliped in the latter are still inadequately described.

We have been able to examine a specimen of J. nocturna through the kindness of Dr L. B. Holthuis of the Rijksmuseum van Natuurlijke Historie, Leiden. This is a male, carapace length 10mm, from Ria de Arosa, Coruna, N.W. Spain (1.5km W. to N. of lighthouse on Rua Isle, depth 24 metres, bottom grey-greenish clay, 28/6/1964, R.M.N.H. Stn. 1.672), now in the Australian Museum. The carapace and rostrum are 12mm in length, while the hand is only 14mm long. The slender, straight, elongated fingers are a little more than 1½ times the length of the palm. The anterolateral margin of the carapace has four minute "thorns" above origin of linea thalassinica, several minute "thorns" below origin and two small, but distinct, teeth immediately below the ?branchiostegal groove. Contrary to Selbie's page 11 description (1914: 98), the ischium of the 3rd maxilliped has a medial crest of 14 strong teeth on the right member, and one of 16 teeth on the left member. The merus of the 3rd maxilliped has two distolateral teeth and the carpus has a strong tooth distally on the lower edge. The new data recorded here have been used in the key to adults of recent species of Jaxea given above. On examination, the branchial formula was found to be exactly as set out for J. novaezealandiae, i.e., there are 18 gills, including an arthrobranch, but no podobranch, on the 1st maxilliped and a podobranch on the 3rd pereiopod. We wish to thank Dr Holthuis for sending this specimen and for answering so readily other questions on the nomenclature and morphology of laomediids.

The adults of Kurian's Adriatic form and of the species known only from larvae taken off New South Wales and Samoa can be expected to be closely allied and very similar to the conservative generic structural "type" now known from two antipodean parts of the world. The absence of Jaxea from the greater part of the Atlantic, its concentration in Mediterranean waters with an extension in European Atlantic coastal waters to the British Isles, its representation by several species in the Indo-West Pacific, coupled with its presence in the Vienna Basin in the Miocene, all point to a Tethyan origin and distribution for this genus of burrowing laomediids.

Notes on Burrowing

Direct evidence for burrowing is slender, though we believe that the animal's general facies, including its lack of pigmentation and reduced cornea, indicate burrow living. Otter trawling on the Evans Bay study area has produced specimens only at night; trawl shots apparently identical as to depth, length of rope, speed, etc., during daylight produced no Jaxea on any occasion. Squilla armata is taken in the same manner in the same hauls and also only at night; it is similarly believed to be a burrowing form, but on stronger evidence as we have numerous burrowing records for intertidal and immediately subtidal species of Stomatopoda. Presumably both J. novaezealandiae and S. armata are trawled at the mouths of their burrows or wandering outside them at night, while in the day both species are below the surface within the burrow systems.

Bottom photographs taken at New Zealand Oceanographic Institute Stn. A 335 in Wellington Harbour show irregular relief and obscure current markings on the surface of the mud, but unfortunately no burrows, holes or signs of animal life are visible in the prints examined. A deep Knudsen dredge haul at this station produced a large ovigerous female J. novaezealandiae with dead shells of the bivalves Nemocardium pulchellum (Gray) (abundant, shells often in pairs) and Neilo australis (Quoy and Gaimard) (uncommon), but no Echinocardium. The dredge haul at VUZ 32, the Petersen grab haul at VUZ 68 and the orange peel grab haul at NZOI Stn. C 228, all produced associated pairs of Jaxea, which may or may not have been sharing the same burrow system.

Laomedia astacina appears to be the only laomediid for which we have direct evidence of burrowing. Sakai (1962: 30) records for his Japanese specimens that they "are hollowers in the muddy sand of tidal zone, their openings of holes circling around with piled sand". It is interesting to note that L. astacina also has a mineral-grain coating like that described above for the New Zealand Jaxea. Sakai (p. 30) records that his animals were "as usual, covered with reddish-brown grain-like particles all over the surface and its hairs, but taking their coverings off from the surface, all the texture turns to white".

Notes on Behaviour in Laboratory

Specimens of Jaxea novaezealandiae taken in Evans Bay on 1/6/1965, were kept alive under observation by R.G.W. for eleven days in a 400 gallon aquarium at page 12 the Victoria University Marine Laboratory at Island Bay, Wellington. The following brief observations on attempted burrowing, locomotion and perception were made during this period and are presented here as a contribution to the biology of this little known animal.

Neither during this period, nor during previous attempts (1957-59) to keep J. novaezealandiae alive, could specimens be induced to take food. All foods normally taken by local Decapoda of similar size, such as fragments of fat-free meat, fish or bivalve were ignored. Though these shrimp tore organic matter to pieces with their chelae, they were not observed to eat anything in captivity. The gradual death of the animal, was possibly due partly to starvation and partly to failure to adjust to substratum differences and consequent inability to burrow. Specimens failed to move in any but minor ways for five or more days till final collapse in the 1957-59 observations. Collapse appeared to indicate shock due to lack of thigmotactic stimulation.

(i)

Attempted Burrowing: Fine silica sand was placed in the Island Bay Laboratory aquarium. This did not permit normal burrowing, but at night Jaxea attempted to burrow actively in different situations against the glass walls or under a small stone overhang. Little activity was observed in daylight. In attempting to burrow, the chelipeds were kept in front of the animal and alternately pushed quite deeply into the sand and withdrawn. The loosened sand was then moved with the 2nd pereiopods. These limbs were the most active pair in burrowing and their broad and flattened propodi appeared to be of great use. The 2nd pereiopods moved more or less in unison; they were pushed into the loose sand under the animal and then moved swiftly to the left or to the right with a load of sand which was hurled out to the side. This digging rate was about one complete movement every second.

The 3rd pereiopods were occasionally used to assist the 2nd, but their main use in burrowing was either to loosen sand as described above for the chelipeds, or more frequently to move in a "breaststroke" swimming manner, in unison, and sweep sand backwards from the surface and throw it out behind the shrimp. The 4th pereiopods were similarly used in a swimming manner, or as stabilisers, when anterior limbs were working. The 5th pereiopods were usually inactive and held mainly against the side of the animal, but occasionally took part in sand moving by swimming action or in stabilising and supporting the shrimp.

(ii) Locomotion: Crawling either forwards or backwards is the usual form of locomotion in J. novaezealandiae. This was assisted at times by movement of the pleopods. Swimming also took place in the aquarium, either forwards or backwards, using the pleopods with the chelipeds extended to the front. When the specimen was disturbed, its abdomen and telson were violently flexed and the animal withdrew wildly and rapidly backwards. When severely agitated Jaxea ceased to move and shammed death.
(iii) Perception: Sight appeared to be very poor or virtually non-existent, but the sense of touch was immediately observable. Jaxea did not react to any surrounding movement within the aquarium, or to any object, till the antennae had made contact; only then did the animal move chelipeds, walking legs or body to avoid or investigate the confronting action or situation. Sight was obviously sufficient to detect day from night, as during daylight hours activity was at a minimum.