Pleistacantha griffini, Ahyong, Shane T. & Lee, Timothy, 2006

Ahyong, Shane T. & Lee, Timothy, 2006, Two new species of Pleistacantha Miers, 1879 from the Indo-West Pacific region (Crustacea, Decapoda, Majidae), Zootaxa 1378, pp. 1-17 : 3-8

Pleistacantha griffini sp. nov.

( Figs 1–3 , 7A–D )

Pleistacantha moseleyi .— Doflein, 1904: 77, pl. 25: fig. 1 [part, Sumatran specimens].— Griffin & Tranter, 1986b: 359 –361 [part, North West Shelf specimens].— Davie, 2002: 297, 298 [North West Shelf records] [not P. moseleyi ( Miers, 1886) ].

Type material. HOLOTYPE: AM P35498, male (cl 78.9+ mm, pcl 64.3 mm, cw 47.8 mm), North West Shelf, Australia, 18°33’S, 117°31’E, 400 m, trawl, RV Soela, 25 Apr 1983. PARATYPES: AM P72686, 1 female (cl 76.2 mm, pcl 56.0 mm, cw 42.8 mm), type locality; AM P35499, 1 female (cl 62.2 mm, pcl 43.7 mm, cw 33.1 mm), North West Shelf, 20°S, 117°40’E, about 400 m, trawl, RV Soela, 2–15 Nov 1983.

Other material examined. Indonesia: MNHN, 1 male (cl 85.8 mm, pcl 66.4 mm, cw 50.8 mm), Tanimbar, 8°42’S, 131°53’E, 356–368 m, beam trawl, CP69, 2 Nov 1991; MNHN, 1 male (cl 52.0 mm), 1 female (cl 72.0 mm, pcl 50.0 mm, cw 37.0 mm), Tanimbar, 8°42’S, 131°53’E, 356–368 m, beam trawl, CP69, 2 Nov 1991.

Description. Carapace pyriform, pcl 1.3–1.4 times width. Rostral spines 0.4 postrostral carapace length; widely separated basally, upcurved, strongly divergent; with 2–4 ventral (excluding basal) spines; proximal half of lateral margin with 2 or 3 widely spaced spines. Orbital margin with 4 or 5 well-spaced spines increasing in size posteriorly: 1–3 small preorbital spines at level of rostral base, larger supraorbital, slender intercalated and postorbital spines. Hepatic spine prominent, anteriorly directed, with 3–6 accessory spines. Dorsal surface densely and evenly covered with short, slender, seta-tipped spines, setae straight. Branchial regions widely separated, barely inflated, not elevated above highest point of cardiac region; cardiac region slightly elevated, as high as or slightly higher than branchial regions, narrowest point exceeding two-thirds narrowest width between upper orbital margins, with several rows of spines separating branchial regions.

Epistome with ventrally directed spine lateral to antennal gland aperture, with single median spine between apertures, and cluster of 4–6 spines midway between aperture and anterolateral angle of buccal cavity; anterolateral angle of buccal cavity crenulate to spinulate.

Eyestalk with elongate, stiff setae on anterior margin; interantennular spine bifurcated in distal half, branches parallel; distal margin of antennular sinus produced to slender ventrolaterally directed spine.

Basal antennular article with 3 ventrally directed spines; basal antennal peduncle article ventrally and distally spinose; penultimate article distally and ventrally spinose; ultimate article with distal and ventral spinule at midlength; flagellum not extending beyond rostral apices.

Third maxilliped merus as wide as ischium; meral surface spinose, with slender spine on either side of carpal articulation, anterolateral margins spiniform; ischium with dentate margins, surface with spines and conic tubercles; with shallow longitudinal groove.

Third sternite of male with spinous median row anteriorly, spinous posteriorly; remaining sternites spinose laterally. Female sternites spinose.

First pleopod of male (G1) gently curving outwards; subdistal papilla on inner margin subequal in length to margin between papilla base and apex; papilla straight, directed perpendicularly to margin; margin proximal to subdistal papilla gently sinuous, without distinct shoulder.

Male abdomen with 7 freely articulating somites; widest at somites 2 and 3; all somites distinctly spinose.

Female abdomen with 7 somites; somites 1–5 spinose medially and laterally; telson granulate; forming ‘operculum’; widest at somite 6.

Male and female chelipeds (P1) similar. Chela slender, markedly spinous; palm, carpus and merus with longitudinal rows of slender, upright spines, longest on lower and inner margins; occlusal margins of dactylus and pollex dentate, with slight gape; cheliped length 1.2 pcl in females, 1.4 pcl in males; dactylus 0.7 palm length.

Walking legs (P2–5) long, slender, decreasing in length posteriorly. P2 about 3.6 times postrostral carapace length in males, 2.6 in females. Spination of articles similar in both sexes: propodus, carpus and merus granular and strongly spinous, with longitudinal rows of long, widely spaced, upright spines and coarse setae; dactyli covered with dense soft setae, lateral margins with row of long, coarse, curved setae, apex sharp, corneous. Dactyli of P2 and P3 about 0.5–0.7 propodus length, those of P4 and P5 about 0.6–0.7 propodus length. P5 merus 0.7 times postrostral carapace length.

Etymology. It is a pleasure to name the new species after Dr. Des Griffin, for his fundamental contributions to our knowledge of the Indo-Pacific majids.

Remarks. Pleistacantha griffini sp. nov. closely resembles P. moseleyi ( Miers, 1886) from the Philippines, with which it was identified by Griffin & Tranter (1986b). Based on comparison of P. griffini with the redescription of the holotype of P. moseleyi by Guinot & Richer de Forges (1982) and topotypic specimens in the ZRC, the two species can be distinguished as follows:

— The relative proximity of the branchial regions of the carapace. In P. m o s e l e y i, the branchial regions are swollen and closely approximated such that only a single row of spines can be accommodated along the midline between the two regions. Conversely, in P. griffini , the branchial regions are less inflated (being somewhat flattened) and more widely separated medially such that several rows of spines are present between the regions.

— In P. griffini the carapace is proportionally narrower than in P. m o s e l e y i, measuring 1.3 pcl:cw versus 1.2 in adults.

— In P. griffini , the P5 merus is proportionally shorter than in P. m o s e l e y i, measuring 0.7 merus length:pcl (both sexes) versus 0.9–1.0 (male) and 0.8 (female) respectively.

— The margin proximal to the subdistal papilla of the G1 is gently sinuous in P. griffini , rather than distinctly stepped, as in P. m o s e l e y i ( Figs. 7A–C , J).

— Sexual dimorphism is not pronounced in the present series of P. griffini . Male P. moseleyi of similar size to known males of P. griffini exhibit the strongly inflated and smoother chelae typical of adults. In P. griffini , however, the male chelae are neither markedly more inflated nor less spiny than in females, and the female abdomens are not yet fully ‘opercular’ indicating that the females are immature. It is likely that male P. griffini will be found to exhibit sexual dimorphism in cheliped form similar to that of P. m o s e l e y i, though obviously at a larger size than in the latter.

Pleistacantha griffini also closely resembles P. pungens (Wood-Mason in Wood- Mason & Alcock, 1891), but as with P. m o s e l e y i, the new species is immediately distinguished by the well-separated branchial regions of the carapace. Although most recent authors have regarded P. pungens as a junior synonym of P. m o s e l e y i, we regard both as distinct species in agreement with Guinot & Richer de Forges (1982); P. pungens will be redescribed in a forthcoming study. Judging from Doflein’s (1904) account, his records of P. m o s e l e y i from Sumatra, the Nicobar Islands, and East Africa are referable to P. griffini , P. pungens and an as yet unidentified Pleistacantha species, respectively.

Distribution. Presently known only from the North West Shelf, Australia, Sumatra and off the Tanimbar Islands, Indonesia; 356– 400 m.

Figures

FIGURE 1. Pleistacantha griffini sp. nov., male holotype, pcl 64.3 mm, cw 47.8 mm, North West Shelf, Australia, AM P 35498. A, carapace. B, dorsal habitus. C, ventral surface. D, anterior view.

FIGURE 2. Pleistacantha griffini sp. nov., male holotype, pcl 64.3 mm, cw 47.8 mm, North West Shelf, Australia, 18 ° 33 ’ S, 117 ° 31 ’ E, AM P 35498. A, carapace, right lateral view. B, anterior carapace, right lateral view. C, right cheliped. D, distal portion of left third maxilliped. E, F, right P 2 distal articles, dorsal and lateral views, respectively.

FIGURE 3. Pleistacantha griffini sp. nov. A – D, female paratype, pcl 43.7 mm, cw 33.1 mm, North West Shelf, Australia, 18 ° 33 ’ S, 117 ° 31 ’ E, AM P 35499. E, female, pcl 50.0 mm, cw 37.0 mm, Tanimbar Islands, Indonesia, CP 69, MNHN. A, carapace, dorsal view. B, carapace, right lateral view. C, ventral surface. D, right cheliped. E, dorsal habitus.

FIGURE 7. A – D, Pleistacantha griffini sp. nov., male holotype, pcl 64.3 mm, cw 47.8 mm, North West Shelf, Australia, 18 ° 33 ’ S, 117 ° 31 ’ E, AM P 35498. E – H, P. m axima sp. nov., male holotype, cl 67.1 mm, cw 53.0 mm, Tai-Shi, I-Lan County, NE Taiwan, ZRC 2005.0116. I, P. o r y x, male, pcl 30.2 mm, cw 22.5 mm, Tungkang, Kaohsiung County, Taiwan, ZRC 2001.0065. J, P. moseleyi, male, pcl 71.3 mm, cw 60.0 mm, Balicasag Island, Philippines, ZRC 2005.0117. A, E, right G 1, sternal view. B, F, I, J, apex of right G 1, sternal view. C, G, apex of right G 1, abdominal view. D, H, anterior margin of buccal cavity. Scale A, E = 2 mm; B, C, F, G, J = 1 mm; I = 0.5 mm; D, H = 4 mm.