Heteroptychus paulae, 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 : 593-597

Heteroptychus paulae n. sp.

Figures 300 , 301

TYPE MATERIAL — Holotype: Solomon Islands. SALOMON 2 Stn CP 2269, 7°45.1’S, 156°56.3’E, 768-890 m, 4.XI.2004, ov. ♀ 4.7 mm ( MNHN-IU-2014-17131 ) . Paratypes: Solomon Islands. SALOMON 2 Stn CP2215, 7°44.3’S, 157°42.3’E, 718- 880 m, 26.X.2004, 1 ov. ♀ 4.1 mm (MNHN-IU-2014-17132) . – Stn CP2246, 7°42.6’S, 156°24.6’E, 664-682 m, 1.XI.2004, 1 ov. ♀ 4.8 mm (MNHN-IU-2013-12293) . – Stn CP2247, 7°44.9’S, 156°24.7’E, 686-690 m, 1.XI.2004, 1 ♂ 4.2 mm ( MNHN- IU-2014-17133) . – Stn CP2248, 7°45.212’S, 56°25.606’E, 673- 650 m, 1.XI.2004, 1 ov. ♀ 5.2 mm (MNHN-IU-2013-12290) . – Stn CP2289, 08°36’S, 157°28’E, 627- 623 m, 07.XI.2004, 1 ♂ 3.8 mm, 1 ov. ♀ 4.2 mm (MNHN-IU-2014-17134) .

ETYMOLOGY„ Name for Paula Martin-Lefevre of the Muséum national d’Histoire naturelle for her contribution to collection and data management on crustaceans.

DISTRIBUTION„ Solomon Islands, in 660- 890 m.

SIZE„ Males, 3.8-5.1 mm; females, 4.2-5.2 mm, ovigerous females from 4.2 mm.

DESCRIPTION„ Small to medium-sized species. Carapace: 0.7-0.8 × as long as broad, greatest breadth 1.9-2.2 × distance between anterolateral spines. Dorsal surface polished, moderately convex from anterior to posterior, ridged along posterior third of lateral margin. Lateral margin strongly convex around posterior third; anterolateral spine prominent, horizontally directed forward but slightly inclined mesially, reaching or slightly falling short of rostral tip. Rostrum relatively broad triangular, with interior angle of 36-48°, straight horizontal, fully reaching or slightly falling short of tip of eye; length 0.6-0.7 × breadth, 0.20-0.27 × length of remaining carapace; distally blunt; dorsal surface flattish but feebly concave basally. Lateral limit of orbit rounded, without spine. Pterygostomian flap very low on posterior half (posterior height 0.2 × anterior height), anteriorly produced to sharp spine; anterior surface well inflated (convex from dorsal to ventral) with 3 or 4 distally blunt coniform processes of small to good size or ridged longitudinally with 2 or 3 small or low processes.

Sternum: Excavated sternum with subtriangular anterior margin, surface with sharp ridge in midline on anterior half. Sternal plastron in males 0.6 × as long as broad; in females, left and right parts of sternites 5-7 discontinuous, interrupted by loss of median parts; lateral extremities of sternites 4-7 slightly convex and slightly divergent posteriorly; sternite 6 broadest. Sternite 3 anterior margin excavated in broad V-shape or semicircular shape, with small blunt (rarely obsolete) median notch lacking flanking spine or process. Sternite 4 with rounded anterolateral margin. Sternite 6 broadest.

Abdomen: Smooth and polished. Somite 1 in profile gently convex from anterior to posterior. Somite 2 tergite 2.2-2.8 × broader than long; pleural lateral margins 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 slightly or very feebly concave on posterior margin, length 1.0-1.3 × that of anterior plate.

Eyes: 1.4-1.6 × as long as broad, subovate. Cornea 0.5-0.7 × length of remaining eyestalk.

Antennule and antenna: Ultimate article of antennular peduncle 3.2-3.8 × longer than high. Antennal peduncle relatively short and slender. Article 2 without lateral spine. Antennal scale distinctly articulated, ending in proximal third or midlength of article 4. Distal 2 articles unarmed; article 5 1.2-1.4 × longer than article 4, breadth 0.4-0.5 × height of ultimate antennular article. Flagellum of 11 or 12 segments directed posterolaterally.

Mxp: Mxp1 with bases broadly separated. Mxp3 basis with 2 obsolescent denticles or unarmed on mesial ridge. Ischium 0.4 × as long as merus, crista dentata with 2-4 denticles on proximal half, 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, 6.9-7.3 × (males), 5.8-7.4 × (females) longer than carapace. Ischium with basally broad, distally blunt distodorsal process and lobe-like proximal process overhanging basis. Merus with 2-4 blunt distodorsal spines (rarely obsolescent, leaving 1 short blunt spine), length 1.4-1.6 × (males), 1.8 × (females) that of carapace. Carpus 1.3-1.4 × longer than merus, unarmed or with several obsolescent blunt spines (in both sexes) along mesial margin. Palm 4.1-4.5 × (males), 4.3-4.7 × (females) longer than broad, 0.6 × (rarely 0.7 x) as broad as high, 0.8 × length of carpus, mesial and lateral margins subparallel, mesial margin roundly or moderately ridged, not cristiform, with or without obsolescent blunt spines. Fingers half as long as palm, gaping in proximal two-thirds, straightly fitting to each other when closed in distal half, relatively slender, distally spooned; opposable margin of movable finger with prominent blunt (truncate) process at midlength of gaping portion, distal to position of opposite process on fixed finger.

P2-4: Setose along prehensile margins of propodi and dactyli. Meri subequal on P2 and P3, P4 merus 0.4-0.5 × length of P3 merus; length-breadth ratio, 5.2-6.4 on P2, 5.3-6.4 on P3, 2.8-3.4 on P4; P2 merus 0.9-1.0 × length of carapace, 1.2- 1.3 × length of P2 propodus, P3 merus 1.2-1.3 × length of P3 propodus, P4 merus 0.6-0.7 × length of P4 propodus. Carpi subequal in length on P2 and P3, P4 carpus one-third length of P3 carpus; subequal to or slightly shorter than propodus on P2 and P3, much shorter (0.31-0.36) on P4; carpus-dactylus length ratio, 1.3-1.5 on P2 and P3, 0.5 on P4. Propodi subequal on P2 and P3 or shorter on P3 than on P2, P4 propodus 0.8-0.9 × length of P3 propodus; propodus-dactylus length ratio, 1.5-1.6 on P2, 1.4-1.7 on P3, 1.3-1.4 on P4; flexor margin concavely curving in lateral view, unarmed. Dactyli subequal on P2-4, dactylus-carpus length ratio, 0.7-0.8 on P2, 0.6-0.8 on P3, 2.0-2.2 on P4; flexor margin with row of 12-14 sharp spines proximally diminishing and slightly inclined, ultimate and penultimate spines subequal or ultimate slightly larger.

Eggs. Number of eggs carried, 13-26; size, 1.00 × 1.08 mm - 1.10 × 1.12 mm (holotype); 1.25 × 1.21 mm - 1.46 × 1.29 mm (paratype, MNHN-IU-2014-17134).

REMARKS„ The female holotype of H. paulae was collected together with the male holotype of H. apophysis n. sp. Initially, these two specimens were thought to be identical, because of the similarity in most characters including the relatively broad rostrum, the absence of lateral orbital spine and lack of paired median spines on the anterior margin of sternite 3. However, the following characters are not observed in all the paratypes including males of H. paulae : the carapace branchial margin with two rounded processes, the anterolateral spine stronger and directed straight forward, and the P1 carpus bearing two rows instead of one row of spines along the mesial margin and the palm mesially cristi- form instead of roundly ridged. It is not unlikely that these are size-related, representing grown male characters, but the differences seem too large. Unfortunately, genetic analyses of this and related material failed (L. Corbari, pers. comm.), but here I propose to treat them as different species.

The antennal scale articulated with article 2 and the relatively long anterolateral spine of the carapace link H. paulae to H. anouchkae n. sp. However, H. paulae differs from H. anouchkae in having the rostrum that is distally blunt instead of sharply pointed and that is relatively broad and more trianguloid with the interior angle of at least 45°, instead of relatively narrow with the interior angle of less than 35°; the greatest breadth of the carapace is measured at the posterior quarter of the lateral margin rather than posterior third; the anterolateral spine of the carapace is horizontal instead of deflected dorsally; the lateral orbital angle is rounded instead of bearing small distinct spine; the anterior margin of sternite 3 is medially notched instead of bearing pair of small processes; and the P1 palm is mesially rounded or moderately ridged, not sharply ridged.

Figures

FIGURE 300 Heteroptychus paulae n.sp.,holotype,ovigerous female4.7 mm (MNHN-IU-2014-17131).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,setae on merus omitted,ventral.G, same,lateral. Scale bars:1 mm.

FIGURE 301 Heteroptychus paulae n. sp.,holotype,ovigerous female 4.7 mm (MNHN-IU-2014-17131).A, left P1, dorsal. B, same,proximal part, lateral.C, same, distal part, setae omitted, mesial. D, same, fixed finger, dorsomesial. E, left P2, lateral.F, same, distal part, setae omitted,lateral.G, left P3,setae omitted, lateral.H, same,distal part, lateral.I, left P4, lateral.Scale bars:1 mm.