Neopilumnoplax nieli, Ahyong, 2008

Ahyong, Shane T., 2008, Deepwater crabs from seamounts and chemosynthetic habitats off eastern New Zealand (Crustacea: Decapoda: Brachyura), Zootaxa 1708 (1), pp. 1-72 : 48-54

Neopilumnoplax nieli sp. nov.

( Figs 22–24 , 29D )

Pilumnoplax heterochir . — Rathbun 1923: 99, pl. 17: figs. 1–2. [Not P. heterochir Studer, 1883 ].

Neopilumnoplax heterochir . — Griffin & Brown 1976: 255. — Poore 2004: 437. [Not N. heterochir ( Studer, 1883) ]. Pilumnoplax sp. — Clark & O’Shea 2001: 15. — Martin & Haney 2005: 451, 495.

Type material. HOLOTYPE: NIWA 29364 , male (cl 14.7 mm, cw 19.0 mm), Builders Pencil cold seep, 39°32.47–32.83’S, 178°19.90–19.95’E, 775–810 m, TAN0616/18, 5 Nov 2006.

PARATYPES: Builders Pencil cold seep: NIWA 29361 , 2 males (cl 4.1–7.2 mm, cw 5.2–9.6 mm) , 2 females (cl 6.4–7.3 mm, cw 8.3–9.5 mm), 39°32.47–32.83’S, 178°19.90–19.95’E, 775–810 m, TAN0616/18, 5 Nov 2006; NIWA 29365 , 2 males (cl 6.3–7.3 mm, cw 7.9–9.3 mm) , 4 females (cl 6.4–9.5 mm, cw 8.1–12.5 mm), 3 ovigerous females (largest, cl 13.0 mm, cw 17.0 mm; others damaged), 39°32.59–32.62’S, 178°20.17–19.72’E, 815– 812 m, TAN0616/21, 5 Nov 2006; NIWA 29366 , 5 males (cl 8.3–13.1 mm, cw 10.9–17.8 mm) , 3 females (cl 7.0–10.0 mm, cw 9.1–13.5 mm; largest ovigerous), 39°32.82–32.64’S, 178°19.71–19.92’E, 810– 786 m, TAN0616/25, 5 Nov 2006; NIWA 29367 , 1 female (cl 11.8 mm, cw 15.8 mm), 39°32.82–32.64’S, 178°19.71–19.92’E, 810– 786 m, TAN0616/25, 5 Nov 2006 ; NIWA 29370 , 2 males (cl 11.2–11.6 mm, cw 8.3–9.5 mm), 1 ovigerous female (cl 10.6 mm, cw 14.9 mm) , 1 female (cl 6.5 mm, cw 8.1 mm; with rhizocephalan), 39°32.61–32.68’S, 178°20.11–19.69’E, 810–817 m, TAN0616/32, 6 Nov 2006; NIWA 29371 , 8 males (cl 6.3–12.2 mm, cw 8.0– 15.6 mm), 6 ovigerous females (cl 9.9–12.0 cw 12.9–15.8 mm) , 6 females (cl 5.9–10.1 mm, cw 7.5–13.5 mm; largest with rhizocephalan), 39°32.59–32.65’S, 178°20.19–19.62’E, 815–819 m, TAN0616/38, 6 Nov 2006; ZRC 2008.0006 , 3 males (cl. 5.1–10.9 mm, cw. 6.2–14.0 mm) , 4 females (cl. 3.7–9.0 mm, cw. 4.1–11.4 mm), 39°32.71–33.01’S, 178°19.83–19.90’E, 790– 815 m, TAN0616/30, 6 Nov 2006.

Other material examined. Seamount 441: NIWA 3588 , 2 males (cl 5.3–10.8 mm, cw 6.4–14.6 mm), 34°02.55–02.95’S, 174°49.02–48.70’E, 880– 792 m, KAH0204/47, 19 Apr 2002 .

Main Cavalli Seamount: NIWA 3584 , 2 damaged males, 2 females (cl 7.3–9.7 mm, cw 9.6–12.4 mm; smaller ovigerous), 34°07.15–07.03’S, 174°09.15–08.89’E, 800– 670 m, KAH0204/07, 14 Apr 2002 ; NIWA 3585 , 1 female (cl 5.0 mm, cw 6.0 mm), 34°06.91–06.84’S, 174°08.70–08.59’E, 640– 610 m, KAH0204/08, 14 Apr 2002 .

West Cavalli Seamount: NIWA 3586 , 1 male (cl 5.0 mm, cw 6.1 mm), 1 female (cl 7.8 mm, cw 9.8 mm), 34°09.72–10.09’S, 173°57.70–57.97’E, 810– 780 m, KAH0204/32, 17 Apr 2002 ;

South Cavalli Seamount: NIWA 3587 , 1 male (cl 8.9 mm, cw 10.8 mm), 34°15.94–15.67’S, 174°06.19– 06.16’E, 850– 840 m, KAH0204/44, 18 Apr 2002 .

SE of Brothers Seamount : NIWA 34928 , 1 ovigerous female (cl 8.8 mm, cw 12.0 mm), 35°01.99’S, 179°15.89’E, 788–803 m, J660, 5 Sep 1974 .

Rumble III Seamount: NIWA 27547 , 4 males, 3 females, 35°44.31’S, 178°29.79’E, 939– 280 m, TAN0107/122, Z10776 , 20 May 2001 .

Rumble V Seamount : NIWA 27551 , 1 female (cl 7.3 mm, cw 9.8 mm), 36°08.35’S, 178°11.55’E, 750– 670 m, TAN0107/229, Z10810 , 24 May 2001 ; NIWA 27552 , 1 male (cl 7.5 mm, cw 10.0 mm), 36°08.29’S, 178°11.75’E, 730– 470 m, TAN0107/324, Z10818 , 24 May 2001 .

Whakatane Seamount: NIWA 6763 , 1 male (cl 14.9 mm, cw 19.3 mm), 1 female (cl 11.4 mm, cw 14.9 mm), 36°48.77’S, 177°27.99’E, 897 m, TAN0413/5, 7 Nov 2004 ; NIWA 6764 , 1 female (cl 12.1 mm, cw 16.3 mm), 37°48.77–48.55’S, 177°27.98–27.76’E, 899–900 m, TAN0413/6, 8 Nov 2004 .

Nukuhou Seamount: NIWA 6765 , 1 male (cl 11.9 mm, cw 15.6 mm), 37°12.47–12.64’S, 177°14.65– 14.55’E, 900– 720 m, TAN0413/45, 10 Nov 2004 ; NIWA 6766 , 2 males (cl 8.7–9.4 mm, cw 11.1–11.8 mm), 37°12.55–12.96’S, 177°14.26–14.21’E, 910– 701 m, TAN0413/59, 11 Nov 2004 ; NIWA 6767 , 1 male (cl 11.2 mm, cw 14.4 mm; with rhizocephalan), 1 ovigerous female (cl 8.7–9.8 mm, cw 12.5 mm), 37°13.45–13.17’S, 177°14.05–14.26’E, 693–698 m, TAN0413/63, 11 Nov 2004 .

Mahina Knoll: NIWA 6770 , 1 male, 1 female, 1 indet., 37°18.97–18.72’S, 177°04.49–04.47’E, 495– 466 m, TAN0413/138, 14 Nov 2004 ; NIWA 6773 , 1 male (cl 11.3 mm, cw 8.6 mm), 37°20.09–20.03’S, 177°04.58–04.98’E, 502– 430 m, TAN0413/174, 16 Nov 2004 ; NIWA 6774 , 1 male (cl 12.0 mm, cw 15.7 mm), 2 ovigerous females (cl 9.2–11.8 mm, cw 11.8–16.1 mm), 37°18.72–18.73’S, 177°03.94–04.26’E, 725– 550 m, TAN0413/177, 16 Nov 2004 .

Ritchie Hill: NIWA 34970 , 3 males (cl 7.5–10.0 mm), 5 females (cl 8.3–8.5 mm; largest ovigerous, 2 with rhizocephala), 39°28.24–27.28’S, 178°24.76–25.17’E, 865– 741 m, KAH9907/40, 3 Jun 1999 .

Rock Garden cold seep: NIWA 29354 , 2 males, 3 females, 40°02.31–02.47’S, 178°08.58–08.62’E, 730– 747 m, TAN0616/06, 4 Nov 2006 ; NIWA 29357 , 2 males, 1 female, 40°02.35–02.41’S, 178°08.62–09.00’E, 764–766 m, TAN0616/07, 4 Nov 2006 ; NIWA 29358 , 1 male (cl 6.9 mm, cw 8.2 mm), 40°02.37’S, 178°08.61’E, 748 m, TAN0616/09, 4 Nov 2006 ; NIWA 29359 , 2 females (cl 6.4–9.6 mm, cw 8.0– 12.6 mm), 40°02.38–02.22’S, 178°08.55–08.86’E, 760– 700 m, TAN0616/10, 4 Nov 2006 ; NIWA 29360 , 6 males (cl 4.8–8.9 mm, cw 5.7–11.5 mm), 6 females (cl 4.9–10.3 mm, cw 5.9–13.5 mm; 5 largest ovigerous), 40°02.41– 02.65’S, 178°08.67–08.91’E, 749–787 m, TAN0616/12 SEL, 4 Nov 2006 ; NIWA 29363 , 1 female (cl 5.8 mm, cw 7.3 mm), 40°02.41–02.65’S, 178°08.67–08.91’E, 749–787 m, TAN0616/12 GVVL, 4 Nov 2006 .

Hihi cold seep, Uruti Ridge: NIWA 29373 , 4 males, 2 females, 41°17.71–17.65’S, 176°33.37–33.66’E, 730–747 m, TAN0616/67, 10 Nov 2006 .

Kereru cold seep, Uruti Ridge: NIWA 29376 , 1 male (cl 8.0 mm, cw 10.2 mm), 2 ovigerous females (cl 10.6–12.7 mm, cw 14.0– 17.3 mm), 41°17.32–17.17’S, 176°35.23–35.49’E, 731– 720 m, TAN0616/70, 10 Nov 2006 .

Scroll Seamount: NIWA 29639 , 1 male (cl 11.1 mm, cw 14.2 mm), 1 female (cl 12.6 mm, cw 16.6 mm), 42°47.09’S, 179°59.77’W, 917–1082 m, TAN0604/07, 28 May 2006 .

Diabolical Seamount: NIWA 29651 , male (cl 15.0 mm, cw 19.7 mm), 42°47.33’S, 179°59.11’W, 960– 1036 m, TAN0604/98, 4 Jun 2006 .

Ghoul Seamount: NIWA 29660 , 1 female (cl 10.9 mm, cw 13.9 mm), 42°47.85’S, 179°59.26’E, 970– 1040 m, TAN0604/111, 7 Jun 2006 ; NIWA 27548 , 1 male (cl 14.5 mm, cw 18.3 mm), 42°48.14–48.29’S, 179°59.27–59.30’E, 1013– 931 m, TAN0104/115, 17 Apr 2001 .

Cascade site, S of Tasmania: NMV J55302 , 6 males (cl 5.9–10.1 mm, cw 7.5–12.5 mm), 7 females (cl 8.0– 13.8 mm, cw 10.3–18.3 mm), 43°55.24–55.47’S, 150°27.53–28.21’E, SS0207/077-012, 10 Apr 2007 ; NMV J55643 , 3 males (cl 8.3–9.6 mm, cw 11.1–12.8 mm), 6 females (cl 6.4–12.7 mm, cw 8.2–16.9 mm), 43°55.24–55.47’S, 150°27.53–28.21’E, SS0207/077-012, 10 Apr 2007 .

Western Australia, Australia: NMV J55720 , 1 fragmented male (cw 13.3 mm), off Albany, 35°26.03– 26.15’S, 118°21.00–21.04’E, 900–915 m, sled, SS10/2005 044 , R. Wilson et al., 25 Nov 2005 .

Diagnosis. Carapace epibranchial ridge well-defined; front divided medially by distinct cleft; first (outerorbital) and second anterolateral teeth fused basally, demarcated by shallow concavity in juveniles but becoming confluent with increasing size. Second anterolateral tooth blunt, apex rounded, subtruncate or emarginate. Third anterolateral tooth larger than fourth tooth, both produced as anteriorly recurved spines, apices sharp. Fourth tooth separated from adjacent tubercle by shallow notch. Sternite 8 visible laterally between abdominal somites 2 and 3. G1 mesial margin lined with small spinules on distal third. Major cheliped smooth, without prominent granules or tubercles (at most finely granular in juveniles). Minor cheliped palm rugose to finely granular, not coarsely granular.

Description. Carapace subhexagonal, 1.3 times wider than long; dorsal surface microscopically rugose, appearing smooth; regions ill-defined; epigastric regions low, slightly swollen; protogastric and hepatic regions slightly swollen, separated by shallow furrow; cardiac region flat; epibranchial ridge well-defined. Front subtruncate in dorsal view, bimarginate, formed by distinct transverse anterior groove; margins gently convex, faintly granular, divided medially by distinct cleft. Supraorbital margin low, separated from front by distinct sinus or notch; margin with fissure or V-shaped notch laterad to midlength. First (outerorbital) anterolateral tooth low, blunt. First and second anterolateral teeth fused basally, demarcated by shallow concavity in juveniles but becoming confluent with increasing size. Second anterolateral tooth blunt, apex rounded, subtruncate or emarginate. Third anterolateral tooth larger than fourth tooth, both produced as anteriorly recurved spines. Fourth tooth separated from adjacent tubercle by shallow notch. Suborbital margin granular; with blunt inner tooth, visible dorsally. Eyestalks with row of granules on inner distal margin. Suborbital, pterygostomial and sub-branchial regions finely granular. Posterolateral and posterior carapace margins almost straight.

Thoracic sternum microscopically granular and finely punctate. Sternites 2 and 3 well demarcated. Sternites 3 and 4 fused, sutures visible laterally. Press-button of abdominal locking mechanism positioned near posterior margin of sternite 5. Anterior end of sternoabdominal cavity reaching midlength of sternite 4. Sutures 4/ 5 and 5/6 medially interrupted. Suture 6/7 and 7/8 complete. Sternites 7 and 8 with median groove. Female gonopore on sternite 5; orifice simple, without cover.

Male abdomen with 6 free somites and telson; surface sparsely pitted; lateral margins concave. Somite 1 broad, slender, shortest medially, lateral margins reaching base of P5 coxae. Somite 2 subrectangular, slightly narrower than somite 1. Somite 3 tranversely subtrapezoid, lateral margins angular. Sternite 8 visible laterally between somites 2 and 3. Somites 4–6 becoming progressively narrower and longer. Telson semicircular. G1 with stout, swollen proximal portion and slender distal portion, medially curving outwards sinuously to open tip; lateral surfaces of distal tenth lined with small spinules; distal third of mesial margin lined with small spinules. G2 sinuous, longer than G1, apex tapering to sharp point; distal portion about half as long as proximal portion.

Female abdomen broad; with 6 free somites and telson; lateral margins convex; surface sparsely pitted. Somite 1 broad, slender, shortest medially, lateral margins reaching base of P5 coxae. Somite 2 subrectangular, slightly narrower than somite 1; lateral margins obtusely rounded. Somite 3 tranversely similar to somite 2 but lateral margins bluntly angular. Somites 1–3 entirely covering space between P5 coxae, sternite 8 not visible. Somites 4–6 becoming progressively narrower and longer. Telson broader than long, rounded.

Third maxilliped minutely and sparsely granular; merus subpentagonal, anteroexternal angle rounded; ischium subrectangular, with submedian sulcus; exopod stout, with small distal tooth, reaching to distal edge of merus. Lateral surfaces of endostome each with pair of longitudinal carinae.

Chelipeds (P1) unequal. Merus relatively short, trigonal; dorsal margin with convex granular ridge bearing small subdistal spine or tubercle; inner distal margin with flat, rounded lobe at articulation with carpus; surfaces otherwise appearing smooth but microscopically granular. Carpus with 2 distinct spines on inner distal margin; surface granular; with shallow transverse subdistal sulcus between articular condyles. Major palm stout, unarmed, surfaces smooth, without prominent granules or tubercles (at most finely granular in juveniles); dorsal margin slightly shorter than fingers; fingers with slight gape; occlusal margins bluntly dentate, apices simple, crossing; fingers pigmented pigmented black throughout length; pigmentation on pollex extending slightly onto manus. Minor palm rugose to finely granular, more pronounced dorsally; fingers about 1.5 times as long as dorsal margin of palm; occlusal margins bluntly dentate, apices simple, crossing; fingers pigmented black throughout length; pigmentation on pollex extending slightly onto manus; dactylus with dorsal ridge; pollex with shallow submarginal sulcus.

Ambulatory legs (P2–5) relatively long, slender, relative lengths P4>P3>P2>P5; P4 longest (2.26–2.59 cl); P4 ischiomerus subequal to cl (0.98–1.09 cl); segments sparsely setose, finely granular, with granulation most pronounced on dorsal margins, becoming finely serrate distally. Dactyli sparsely setose, ventral margin with corneous robust setae, dorsal margin with few small corneus setae, apex corneous. P2–5 dactyli elongate, flattened, almost straight; relative lengths P4>P3>P2>P5. P5 dactylus slightly longer than propodus dorsal margin; faintly deflected dorsad; two-thirds as long as P4 dactylus.

Etymology. Named for fellow carcinologist, Niel Bruce, for his contributions to Indo-Pacific carcinology.

Remarks. Serène in Guinot (1969) included three species his new genus Neoplimunoplax: N. heterochir ( Studer, 1883) (type locality: southwestern Africa), N. americana ( Rathbun, 1898) (type locality: Gulf of Mexico, off Georgia, U.S. A), and N. sinclairi ( Alcock & Anderson, 1899) (type locality: off the Travancore coast, India). Tavares & Guinot (1996) added a fourth species, N. gervaini Tavares & Guinot, 1996 (type locality: Guadeloupe, Caribbean Sea). Neopilumnoplax nieli sp. nov. is the first Pacific representative of the genus and most closely resembles N. heterochir , with which it has been misidentified in records from southeastern Australia ( Rathbun 1923; Griffin & Brown 1976; Poore 2004). The single record of N. heterochir from the South China Sea ( Serène & Lohavanijaya 1973) is based on a species of Mathildella , probably M. serrata ( Sakai, 1974) ( Guinot & Richer de Forges 1981b) .

Neopilumnoplax nieli and N. heterochir are readily distinguished by the form of the anterolateral carapace teeth, rugosity of the cheliped palms and spination of the G1. In N. heterochir , the second and third anterolateral teeth are triangular in small specimens, but by 13 mm cl, become blunt and obtuse (see Guinot & Richer de Forges 1981a: pl. 3 fig. 1, 1a; specimen 13 x 17.2 mm but miscaptioned as 11.5 x 15 mm). In contrast, the second and third anterolateral teeth of N. nieli are acute spines with anteriorly recurved apices (especially for the second), even in the largest specimens ( Fig. 24A, J–O ). The cheliped palms of N. nieli are smoother than in N. heterochir . The minor cheliped of N. nieli is somewhat rugose or finely granular rather than being covered with prominent granules in as N. heterochir . Similarly, the major cheliped palm of N. nieli is smooth (or at most finely granular in juveniles) rather than distinctly granular proximally as in N. heterochir . The mesial margin of the G 1 in N. nieli is lined with spines along the distal half of the slender distal portion ( Fig. 24E–F ), rather than the distal third in N. heterochir . Neopilumnoplax nieli can be distinguished from N. americana by the prominent rather than obsolete epibranchial ridge ( Fig. 22B ), and from N. sinclairi and N. gervaini by the blunt and indistinct, rather than spiniform last anterolateral tooth ( Fig. 24A ).

Neopilumnoplax nieli reaches a maximum size of at least 15.0 mm cl. Females are ovigerous by 7.3 mm cl and males have well-developed gonopods by 6.3 mm cl Apart from typical sexually dimorphic features (such as abdomen shape), the present series of N. nieli is morphologically uniform, including the presence of two inner carpal cheliped spines, even in the smallest specimen (male paratype, 4.1 x 5.2 mm, NIWA 29361 ) . The shape and acuteness of the anterolateral carapace spines may exhibit significant allometric variation in many goneplacids, but in N. nieli , the second and third anterolateral carapace spines are sharp and well-developed irrespective of size. The only significant variation is in the form of the first anterolateral tooth, which becomes confluent with the outerorbital tooth with increasing size; the apex ranging from a rounded to bluntsubtruncate or emarginate lobe ( Fig. 24A, J–O ). Five specimens were infected by rhizocephala (male, NIWA 6767 ; female, NIWA 29370 ; female, NIWA 29371 ; two females, NIWA 34970 ) .

Pilumnoplax incerta Cano, 1889 (type locality: unknown; male holotype 6.5 x 8.0 mm), known only from the type description was reported by Cano to closely resemble N. heterochir , differing chiefly by its smooth rather than granular chelipeds. By implication, P. incerta should also resemble N. nieli , particularly in view of the smooth chelipeds in contrast to N. heterochir . Pilumnoplax incerta , however, was described and figured as having a single inner carpal spine and as such, cannot be identified as N. nieli , nor any species of Neopilumnoplax , all of which bear two inner carpal spines. Also, Pilumnoplax Stimpson, 1858 (type species Pilumnoplax sulcatifrons Stimpson, 1858 ) is a junior subjective synonym of Eucrate de Haan, 1835 (type species: Cancer (Eucrate) crenatus de Haan, 1835 ), to which Cano’s species does not correspond. Thus, the generic position of Pilumnoplax incerta is unclear, but it is perhaps referable to Machaerus Leach, 1814 , or Thalassoplax Guinot, 1969 . In particular, the respective type species of both of these genera, M. oxyacanthus ( Monod, 1956) (from off West Africa) and T. angusta Guinot, 1969 (from off Florida), generally resemble Cano’s figure, and most importantly, have a single inner carpal spine and an enlarged, pointed, penultimate anterolateral tooth on the carapace.

Neopilumnoplax nieli appears to be common on seamounts and cold seeps off eastern New Zealand, where it can be sympatric with Pycnoplax victoriensis ( Rathbun, 1923) , and Dorhynchus ramusculus ( Baker, 1906) .

Distribution. Presently known only from New Zealand, southeastern and southwestern Australia; 275– 810 m; 232–494 m ( Rathbun 1923). The known New Zealand range includes cold seeps and seamounts between the southern Kermadec Ridge and Chatham Rise.

Figures

FIGURE 22. Neopilumnoplax nieli sp. nov., male holotype, cl 14.7 mm, cw 19.0 mm (NIWA 29364). A, dorsal habitus. B, carapace, dorsal view.

FIGURE 23. Neopilumnoplax nieli sp. nov., male holotype, cl 14.7 mm, cw 19.0 mm (NIWA 29364). A, anterior. B, ventral. C, right chela. D, right cheliped carpus and merus. E, left chela. F, right P4–5.

FIGURE 24. Neopilumnoplax nieli sp. nov. A–G, male holotype, cl 14.7 mm, cw 19.0 mm (NIWA 29364). H–I, female paratype, cl 11.8 mm, cw 15.8 mm (NIWA 29367). J, female paratype, cl 5.9 mm, cw 7.5 mm (NIWA 29371). K, female paratype, cl 7.0 mm, cw 9.1 mm (NIWA 29366). L, male paratype, cl 8.3 mm, cw 10.9 mm (NIWA 29366). M, ovigerous female paratype, cl 10.0 mm, cw 13.1 mm (NIWA 29366). N, ovigerous female, cl 10.3 mm, cw 13.5 mm (NIWA 29360). O, male, cl 15.0 mm, cw 19.7 mm (NIWA 29651). A, J–O, carapace outline, right anterior and anterolateral margin. B, right third maxilliped. C, endostome, right half. D, H, abdomen. E–F, right G1, abdominal view and sternal view of apex. G, right G2, abdominal view. I, female gonopores. Scale A, D, H–O = 2.5 mm; B, C = 2.0 mm; E, G = 0.8 mm. CX5 = coxa of P5. ST8 = sternite 8.

FIGURE 29. A, Pycnoplax meridionalis (Rathbun, 1923), male, cl 20.9 mm (NIWA 29658). B, Pycnoplax victoriensis (Rathbun, 1923), male, cl 10.4 mm (NIWA 6736). C, Mathildella mclayi sp. nov., female paratype, cl 11.9 mm (NIWA 6769). D, Neopilumnoplax nieli sp. nov., male paratype, cl 15.0 mm (NIWA 29651). E, Miersiella haswelli (Miers, 1886), male, cl 7.8 mm (NIWA 6760). F, Miersiella haswelli (Miers, 1886), ovigerous female, cl 7.1 mm (NIWA 6760). Photo credits: C. Marriot (A, D), R. Stewart (B–C, E–F).