Alijinocaris

Komai, Tomoyuki & Segonzac, Michel, 2005, A revision of the genus AlIJinocaris Williams and Chace (Crustacea: Decapoda: Caridea: Alvinocarididae), with descriptions of a new genus and a new species of AlIJinocaris, Journal of Natural History 39 (15), pp. 1111-1175 : 1152-1155

AlIJinocaris breIJitelsonis Kikuchi and Hashimoto, 2000

( Figures 21 , 22 , 29 ) Alυinocaris breυitelsonis Kikuchi and Hashimoto 2000, p 136 (part), Figures 1 , 2 [type

locality: Depression C, Minami-Ensei Knoll, Okinawa Trough, 28 ° 23.359N ,

127 ° 38.389E, 705 m].

Material examined

Okinawa Trough. DS Shinkai 2000 : dive 547, Depression C, Minami-Ensei Knoll , 28 ° 23.359N, 127 ° 38.389E, 705 m, 3 June 1991, suction sampler, coll. J. Hashimoto, one ovigerous female CL 13.8 mm (holotype; NSMT-Cr 12454) .

Description

Body moderately robust.

Rostrum ( Figure 21A, B ) directed forward, slightly curved dorsally, 0.55 times carapace length, reaching distal margin of second segment of antennular peduncle; dorsal margin armed with 13 teeth, including eight teeth on rostrum proper and five relatively large teeth on carapace posterior to orbital margin, posteriormost tooth arising from 0.38 of carapace length; ventral margin armed with seven small teeth on anterior 0.60. Carapace ( Figure 21A, C ) 0.70 times as wide as long; postrostral median ridge high, extending to 0.70 of carapace length, dorsal angle about 150 °; pterygostomian tooth weakly produced anteriorly, subequal in size to antennal tooth, slightly exceeding antennal tooth; postantennal groove obsolete; branchial region not particularly inflated.

Third abdominal pleuron unarmed. Fourth abdominal pleuron ( Figure 21D ) with three tiny teeth on posteroventral margin. Fifth abdominal pleuron with strong posteroventral tooth and one additional tooth on posterior margin. Sixth abdominal somite 1.40 times longer than proximal height. Telson ( Figure 21E ) falling somewhat short of posterior margin of uropodal endopod, length 2.70 times anterior width and 4.30 times posterior width; armed with six or seven dorsolateral spines; posterior margin ( Figure 21F ) moderately convex, armed with six pairs of spines (second pair longest and third pair shortest) and two pairs of plumose setae subequal in length to longest second spine.

Antennular peduncle ( Figure 21B ) moderately stout, second segment 1.80 times as long as wide. Antennal scale ( Figure 22A ) half length of carapace, 1.87 times longer than wide; lateral margin straight, weakly diverging anteriorly against dorsal median ridge; distolateral tooth moderately broad, directed anteriorly, not reaching broadly rounded distal margin of blade.

First pereopod ( Figure 22B ) as illustrated; greatest height of palm 0.48 length of chela ( Figure 22C ); dactylus ( Figure 22C ) subequal in length to palm. Third pereopod ( Figure 22D ) moderately slender; dactylus ( Figure 22E ) with accessory spinules increasing in size distally; carpus 0.68 times as long as propodus; merus about 7.30 times as long as greatest height.

Size

Only the ovigerous female holotype is known for this species. CL 13.8 mm. TL ca 57 mm.

Distribution and habitat

Known only from the type locality in Minami-Ensei Knoll ( Figure 29 ), at a depth of 705 m. This species occurs at a hydrothermally influenced area. Alυinocaris dissimilis sp. nov. and Shinkaicaris leurokolos comb. nov. occurred sympatrically.

Remarks

Re-examination of the type series and some of the non-type specimens referred to A. breυitelsonis by Kikuchi and Hashimoto (2000) has disclosed that two species of Alυinocaris, one unidentified species of Opaepele and Shinkaicaris leurokolos comb. nov. were confounded by these authors. The paratypes of A. breυitelsonis and non-type specimens referred to A. breυitelsonis are here assigned to A. dissimilis sp. nov. This new species is readily separated from A. breυitelsonis by having far fewer ventral teeth on the rostrum and by the setal fringe of the posterior margin of the telson. So far, A. breυitelsonis is represented only by the holotype.

The possession of more than two pairs of spines on the posterior margin of the telson links A. breυitelsonis to A. lusca and A. stactophila . As Kikuchi and Hashimoto (2000) correctly pointed out, the shorter telson, which falls short of the posterior end of the uropod, distinguishes A. breυitelsonis from A. lusca . Other differences among the three species are discussed under ‘‘Remarks’’ for A. lusca .

It is interesting to compare A. breυitelsonis with A. longirostris because of their superficial similarity and the proximity of the known localities. Other than the armature of the posterior margin of the telson, A. breυitelsonis differs from A. longirostris in the less produced pterygostomian tooth of the carapace.

Figures

Figure 1. Diagrammatic Alυinocaris, showing measurements used in text. (A) Carapace and rostrum, lateral; CL, carapace length; DA, dorsal angle; RL, rostral length. (B) Carapace, dorsal: CW, carapace width. (C) Anterior part of carapace and cephalic appendages, dorsal; L, length; W, width. (D) Sixth abdominal somite, lateral; L, length; H, height. (E) Telson, dorsal; AW, anterior width; L, length; PW, posterior width. (F) Antennal scale, dorsal; abbreviations as in (C). (G) Chela of first pereopod, lateral; PL, palm length; PH, palm height.

Figure 2. Alυinocaris muricola Williams, 1988. Left appendages. (A) Antennal scale, dorsal; (B) mandible, dorsal; (C) maxillule, ventral; (D) maxilla, ventral; (E) first maxilliped, ventral; (F) endopod of first maxilliped, dorsal; (G) second maxilliped, ventral; (H) first pleopod, ventrolateral; (I) endopod of first pleopod; (J) appendices interna and masculina of second pleopod, mesial. (A–H) Female from Régab site, west equatorial African margin (CL 16.8 mm; MNHN-Na 14277); (I, J) male from same locality (CL 15.4 mm; Ifremer).

Figure 21. Alυinocaris breυitelsonis Kikuchi and Hashimoto, 2000. (A) Carapace and cephalic appendages, lateral; (B) anterior part of carapace and cephalic appendages, dorsal; (C) carapace, dorsal; (D) third to sixth abdominal somites, lateral; (E) telson and left uropod, dorsal; (F) posterior margin of telson, dorsal. Holotype ovigerous female from Minami Ensei Knoll, Mid-Okinawa Trough (CL 13.8 mm; NSMT-Cr 12454).

Figure 22. Alυinocaris breυitelsonis Kikuchi and Hashimoto, 2000. (A) Right antennal scale, dorsal (marginal setae omitted); (B) right first pereopod, lateral; (C) chela of right first pereopod, outer; (D) right third pereopod, lateral; (E) dactylus and distal part of propodus of right third pereopod, lateral. Holotype ovigerous female from Minami Ensei Knoll, Mid-Okinawa Trough (CL 13.8 mm; NSMT-Cr 12454).

Figure 29. Distribution map of Alυinocaris species known at present.