Heteroptychus colini, Baba, 2018

Baba, Keiji, 2018, Chirostylidae of the Western and Central Pacific: Uroptychus and a new genus (Crustacea: Decapoda: Anomura), Tropical Deep-Sea Benthos (Mémoires du Muséum national d'Histoire naturelle 212), pp. 1-612 : 586-589

Heteroptychus colini n. sp.

Figures 296 , 297

TYPE MATERIAL — Holotype: Wallis and Futuna Islands. MUSORSTOM 7 Stn CP552, 12°16’S, 177°28’W, 786-800 m, 18.V.1992, ♂ 4.3 mm ( MNHN-IU-2014-17126 ) . Paratypes: New Caledonia, Norfolk Ridge. BIOCAL Stn CP75, 22°20’S, 167°23’E, 825-860 m, 04-05.IX.1985, 1 ♂ 3.6 mm (MNHN-IU-2014-17127) . Fiji Islands. BORDAU 1 Stn DW1417, 16°27’S, 178°55’W, 353 m, 27.II.1999, 1 ♂ 4.5 mm (MNHN-IU-2014-17128) .

ETYMOLOGY„ Named for Colin L. McLay of the University of Canterbury for his friendship and help in reading many of my manuscripts.

DISTRIBUTION„ Fiji Islands, Wallis and Futuna Islands and Norfolk Ridge; 353- 860 m.

SIZE„ Males, 3.6-4.5 mm.

DESCRIPTION„ Small species. Carapace: 0.7 × as long as broad, greatest breadth measured at posterior third, 2.2 × distance between anterolateral spines. Dorsal surface polished, somewhat convex from anterior to posterior or slightly depressed between gastric and cardiac regions, ridged along posterior half of lateral margin. Lateral margins convexly divergent posteriorly; anterolateral spine prominent, horizontally directed straight forward or slightly inclined mesially, ending in distal quarter of rostral length. Rostrum distally narrow triangular, with interior angle of 27-29°, straight, directed somewhat dorsally, reaching tip of eye; length 0.7 × breadth, 0.3 × length of remaining carapace; dorsal surface flattish. Lateral limit of orbit angular and acuminate. Pterygostomian flap anteriorly produced to sharp strong spine; anterior surface smooth and well inflated; posterior height 0.1 × anterior height.

Sternum: Excavated sternum with subtriangular anterior margin, surface with sharp ridge in midline on anterior half. Sternal plastron half as long as broad; lateral extremities of sternites 4-7 convexly divergent posteriorly; sternite 6 broadest. Sternite 3 having anterior margin broadly and deeply excavated, with pair of blunt submedian processes.

Abdomen: Smooth and polished. Somite 1 gently convex from anterior to posterior. Somite 2 tergite 2.7 × broader than long; pleural lateral margin slightly concave, strongly divergent posteriorly, ending in blunt tip. Pleura of somites 3-4 ending in rounded margin. Telson 0.4 × as long as broad; posterior plate feebly concave on posterior margin, length 1.2-1.3 × that of anterior plate.

Eyes: 1.8-1.9 × as long as broad, subovate. Cornea 0.5 × length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 2.9-3.0 × longer than high. Antennal article 2 without lateral spine (with spine on left side in male MNHN-IU-2014-17128). Antennal scale articulated, relatively narrow, terminating in midlength of article 4. Distal 2 articles unarmed; article 5 1.2 × longer than article 4, breadth 0.4-0.5 × height of ultimate antennular article. Flagellum of 12 segments.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 1 denticle near distal end of mesial ridge. Ischium 0.4 × as long as merus, crista dentata without denticles, flexor margin not rounded distally. Merus relatively thick mesio-laterally, with rounded ridge along flexor margin, unarmed. No spine on carpus.

P1: Smooth and nearly glabrous except for fingers, length 5.9-7.1 that of carapace. Ischium with lobe-like distodorsal process and short blunt proximal process overhanging basis. Merus with 2 distomesial spines (distodorsal strong, distoventral small), length 1.5-1.6 × that of carapace. Carpus 1.4 × longer than merus, dorsally with 3 or 4 terminal spines, mesially with row of 7-9 short blunt spines subparalleling ventromesial row of smaller spines, ventral distomesial and distolateral spines small. Palm 2.7-3.2 × longer than broad, 0.7 × as broad as high, 0.8-0.9 × length of carpus; mesial margin not cristiform but weakly ridged. Fingers inclined laterally, gaping in proximal two-thirds, straightly fitting to each other in distal third when closed; relatively slender, distally spooned; movable finger 0.6-0.7 × length of palm, opposable margin with prominent distally blunt process at midlength of gaping portion, distal to position of opposite truncate process on fixed finger.

P2-4: Sparsely setose on meri and carpi, thickly so along prehensile margins of propodi and dactyli. Meri slightly longer on P3 than on P2, P4 merus 0.4 × length of P3 merus; length-breadth ratio, 4.8-5.7 on P2, 4.7-5.7 on P3, 2.3-2.9 on P4; P2 merus 0.9-1.0 × length of carapace, 1.2 × length of P2 propodus, P3 merus 1.2 × length of P3 propodus, P4 merus 0.6-0.7 × length of P4 propodus. Carpi subequal in length on P2 and P3, P4 carpus 0.3-0.4 × length of P3 carpus; carpusdactylus length ratio, 1.1-1.2 on P2, 1.1-1.3 on P3, 0.4-0.5 on P4. Propodi subequal on P2 and P3, P4 propodus 0.8 × length of P3 propodus; propodus-dactylus length ratio, 1.3-1.4 on P2 and P3, 1.2 on P4; flexor margin concavely curving in lateral view, unarmed. Dactyli subequal on P2-4 or slightly shorter on P4, dactylus-carpus length ratio, 0.8-0.9 on P2 and P3, 2.1-2.3 on P4; flexor margin with row of sharp spines (16 on P2, 14-18 on P3, 15-16 on P4) proximally diminishing and perpendicular to margin, ultimate spine subequal to or slightly longer than penultimate spine.

REMARKS — The male from the Fiji Islands (MNHN-IU-2014-17128) is different from the others in the shape of sternite 3: the excavated anterior margin is medially more produced anteriorly bearing pair of median spines.

Among the species possessing the articulated antennal scale, H. colini n. sp., H. anouchkae n. sp. and H. edwardi ( Kensley, 1981) are grouped together by having a distally narrowed rostrum, whereas H. apophysis n. sp., H. paulae n. sp. and H. scambus ( Benedict, 1902) have a broad rostrum. Heteroptychus colini differs from H. anouchkae in having the rostrum distinctly overreaching instead of falling short of the eye, in having the anterolateral spine of the carapace horizontal rather than dorsally deflected, barely reaching instead of overreaching the apex of the rostrum, and in having an angular or acuminate lateral orbital angle instead of a small but distinct spine. The original description of H. edwardi ( Kensley, 1981) from the western Indian Ocean off South Africa is rather brief, but the following characters may discriminate it from H. colini . The rostrum is distally more slender (Kensley used “spiciform”); the anterior margin of sternite 3 bears a median notch, lacking a pair of median processes; the lateral limit of orbit is rounded (Kensley described “anterior margin sinuous between rostrum and anterolateral spine”) instead of acuminate; and according to the description, the pterygostomian flap anteriorly ends in a short spine instead of being strongly produced.

Figures

FIGURE 296 Heteroptychus colini n. sp., holotype, male 4.3 mm (MNHN-IU-2014-17126). A, carapace and anterior part of abdomen, dorsal. B, same, lateral. C, sternal plastron,with excavated sternum and basal parts of Mxp1. D, telson.E, right antenna,ventral.F, right Mxp3, ventral.Scale bars:1 mm.

FIGURE 297 Heteroptychus colini n. sp., holotype, male 4.3 mm (MNHN-IU-2014-17126). A, right P1, dorsal. B, same, distal part, mesial. C, left P2, setae omitted, lateral. D, same, distal part, lateral. E, left P3, lateral.F, left P4, lateral.G, same, distal part, lateral.Scale bars:1 mm.