Chorocaris parva Komai & Tsuchida 2015, sp. nov.
Creators: name: Komai, Tomoyuki
name: Tsuchida, Shinji
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Alvinocarididae
Chorocaris
Chorocaris parva

description: Chorocaris parva sp. nov.
(Figures 1–5)
Material examined
Holotype. Wave Mercury 2007 (Luk Luk) Campaign, dive 28, South Su site, Manus Basin, Bismarck Sea, 03°08.09 ʹ S, 152°10.5 ʹ E, 1310 m, 10 April 2007, ovigerous female (cl 8.0 mm), CBM-ZC 11,939.
Paratype
Manus Basin. Same data as holotype, 1 male (cl 6.9 mm), CBM-ZC 11940; same data as holotype, 33 males (cl 4.3–6.8 mm), CBM-ZC 11941; same data as holotype, 18 females (cl 4.5–7.8 mm), 5 ovigerous females (cl 5.7–6.7 mm), CBM-ZC 11942; dive 30, South Su, 3°08.09 ʹ S, 152°10.5 ʹ E, 1305 m, 11 April 2007, 2 males (cl 5.2, 5.9 mm), 1 female (cl 7.1 mm), CBM-ZC 11944; dive 34, same site, 1310 m, 14 April 2007, 14 males (cl 4.3–6.8 mm), 11 females (cl 4.0– 7.5 mm), 3 ovigerous females (cl 5.5– 6.5 mm), OUMNH. ZC.2014–01-014. RV Yokosuka, YK 06-13 cruise, DS Shinkai 6500, dive #982, PACMANUS site, 03°43.608 ʹ S, 151°40.328 ʹ E, 1684 m, 20 September 2006, 2 specimens (not measured; DNA extracted, preserved in frozen condition), JAMSTEC 070101–070102.
Description
Body integument with scattered minute setae.
Rostrum (Figures 2A, B; 5A, B) reaching (males) or falling short of (females) midlength of first segment of antennular peduncle, tip blunt in dorsal view; ventral surface slightly convex; lateral margin merging into orbital margin. Carapace (Figures 1, 2A–C; 5A, B) with dorsal surface slightly sloping down anteriorly to rostrum, almost glabrous or with few minute setae anteriorly; orbital margin evenly concave; antennal tooth acute or subacute; pterygostomial angle not markedly produced, terminating in subacute or acute point.
Third pleonal pleuron (Figures 1, 2D) broadly rounded; fourth pleuron with blunt or subacute posteroventral angle, no additional denticles; fifth pleuron with posterolateral angle produced into sharp or blunt tooth (sometimes different between right and left), posterior margin above angle slightly sinuous or slightly convex, unarmed. Sixth pleomere 1.4–1.5 times longer than fifth pleomere and 1.4–1.5 times longer than high, with acute posteroventral tooth, posterolateral process terminating in sharp tooth. Telson (Figure 2E) falling well short of posterior margins of uropods, slightly narrowed posteriorly, about 2.5 times longer than anterior width, armed with six to eight dorsolateral spines; posterior margin convex, with two pairs of spines at lateral angles (mesial pair longer than lateral pair), minute median tooth, and 20–24 long plumose setae (Figure 2F).
Eyes (Figure 2A,B) broadly fused with faint median notch, lacking setae on anterior surface.
Antennular peduncle (Figure 2A, B) stout, falling slightly short of or reaching distal margin of antennal scale. First segment with moderately large distolateral tooth and small distomesial tooth and blunt proximolateral tubercle; stylocerite slender, slightly curved mesially, nearly reaching distal margin of second segment. Second segment with distomesial tooth larger than corresponding tooth on first segment.
Antennal peduncle (Figure 2A, B, G) stout. Basicerite with ventrodistal tooth extending as far as dorsodistal projection and often with blunt tooth arising from ventral surface. Fifth segment (= carpocerite) slightly overreaching midlength of antennal scale. Antennal scale suboval, 0.3–0.4 times as long as carapace, about 2.0 times longer than wide; distolateral tooth acute or subacute, closely approximated to lamella (Figure 2H).
Mouthparts typical of family (for detailed description, see Komai and Segonzac 2003, 2005; Komai et al. 2007), as figured (Figure 3A–F). Endopod of maxillule with one apical plumose seta at inner distal angle and one subterminal seta arising from base of outer lobule (Figure 3B). Maxilla (Figure 3C) with moderately broad scaphognathite, devoid of bacteriophore setae on ventral surface; posterior lobe elongate, triangular. Endopod of first maxilliped somewhat compressed, twoarticulated (Figure 3E). Second maxilliped (Figure 3F) with moderately stout endopod; epipod roundly triangular, with simple rudimentary podobranch. Third maxilliped (Figure 4A) not reaching distal margin of antennal scale, moderately slender; ultimate segment tapering distally in subtruncate tip bearing two unequal spines (Figure 4B), with row of spiniform setae on lateral ridge; epipod unequally bilobed (Figure 4C).
First pereopod (Figure 4D) moderately slender, not polymorphic, reaching beyond antennal carpocerite by length of fingers, otherwise typical of family; chela (Figure 3G, H) subequal in length to carpus. Second pereopod (Figure 4E) extending to near distal end of antennal scale; chela and carpus about equal in length; fingers each terminating in distally curved, crossing tip, cutting edge pectinated with row of minute spinules; dactylus about 1.1 times as long as palm (Figure 3J). Third pereopod (Figure 4F) overreaching antennal scale by full length of propodus; dactylus somewhat compressed laterally, 0.15–0.20 times as long as propodus, terminating in strong, curved unguis, flexor surface with six to ten spinules arranged in two rows (Figure 3K, L); propodus with two rows of spinules on flexor surface, mesial row with fewer spinules (Figure 3M); carpus 0.70–0.75 times as long as propodus; ischium usually unarmed, but rarely with one minute spine ventrolaterally. Fourth pereopod (Figure 4G) similar to third pereopod in structure; ischium always unarmed. Fifth pereopod (Figure 4H) generally similar to third and fourth; dactylus similar to those of third and fourth pereopods (Figure 3N, O); propodus with lateral row of spinules consisting of six sets of two or three spinules followed by a single row of spinules, mesial row consisting of more widely spaced spinules (Figure 3P); propodus and carpus combined distinctly longer than merus and ischium combined; ischium always unarmed.
Endopod of male first pleopod (Figure 5C) bilobed distally, mesial lobe prominent, with three or four long spiniform setae directed mesially, lateral lobe obsolete; mesial margin with row of spiniform setae, proximal few plumose, lateral margin with four spiniform setae in distal 0.3 and with some plumose setae in proximal 0.6. Appendix masculina of second pleopod (Figure 5D) stout, subequal in length to appendix interna, armed distally with six to eight spiniform setae. Uropod (Figure 2E) with protopod bearing terminally blunt posterolateral process; exopod with two subequal spines at posterolateral angle.
Size
Males cl 4.3–6.8 mm; females cl 3.2–7.8 mm, ovigerous females cl 5.7–6.7 mm.
Coloration
Not known.
Distribution
Known only from two hydrothermal vent sites in Manus Basin, southwestern Pacific: South Su site, 1305–1310 m; PACMANUS site, 1684 m depth.
Remarks
Chorocaris parva sp. nov. is morphologically most similar to C. susannae comb. nov. known from the southern Mid-Atlantic Ridge in having the pterygostomial angle of the carapace only slightly produced, having less numerous accessory spinules on the flexor faces of the third to fifth pereopods (six to eight arranged in two rows versus 10–16 arranged in three or four rows) and in its relatively small body size (maximum cl <8.0 mm). In the other four species of Chorocaris, the pterygostomial angle of the carapace is produced into a prominent tooth (C. paulexa, C. vandoverae and C. variabilis sp. nov.) or a broadly rounded lobe (C. chacei); and the body size is larger (attaining more than 8.0 mm cl). This new species is morphologically distinguished from C. susannae by the following characters: (1) the fourth pleonal pleuron is unarmed in C. parva, rather than armed with a posteroventral tooth and additional marginal denticles as in C. susannae; (2) the fifth pleonal pleuron bears only a posteroventral tooth in C. parva, whereas it is armed with up to three denticles on the posterolateral margin in addition to having a posteroventral tooth in C. susannae, is frequently only bluntly pointed in C. parva, rather than terminating in an acute tooth in C. susannae.
Etymology
The Latin parvus (= small), in reference to the small body size of this new species.
description: Published as part of Komai, Tomoyuki & Tsuchida, Shinji, 2015, New records of Alvinocarididae (Crustacea: Decapoda: Caridea) from the southwestern Pacific hydrothermal vents, with descriptions of one new genus and three new species, pp. 1789-1824 in Journal of Natural History 49 (29) on pages 1793-1800, DOI: 10.1080/00222933.2015.1006702, http://zenodo.org/record/4000223