Pleistacantha maxima Ahyong & Lee, 2006, sp. nov.
Creators: name: Ahyong, Shane T.
name: Lee, Timothy
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Inachidae
Pleistacantha
Pleistacantha maxima

description: Pleistacantha maxima sp. nov.
(Figs 4–6, 7 E–H)
Pleistacantha moseleyi.— Sakai, 1938: 235, pl. 34: fig. 3 [specimen from Miyazaki] — Gordon, 1963: 153 [specimen from Tosa Bay] [not P. mo sel eyi (Miers, 1886)].
Pleistacantha orynx [sic].— Takeda & Miyake, 1969: 492 –493 [part] [not P. o r y x Ortmann, 1893] [not P. o r y x Ortmann, 1893].
Pleistacantha oryx.— Sakai, 1976: 172 –174, fig. 93 [part].— Miyake, 1983: 29, pl. 10: fig. 1.— Griffin & Tranter, 1986a: 51 –52 [part, ‘large’ specimens].— Davie & Short, 1989: 179 –180, fig. 14A [part, Australian specimen].— Ikeda, 1998: 32, 94–95, pl. 28: figs 1–6.— Ng, Wang, Ho & Shih, 2001: 13 [not P. o r y x Ortmann, 1893].
Type material. HOLOTYPE: ZRC 2005.0116, male (pcl 102.9 mm, cl 67.1 mm, cw 53.0 mm), Tai-Shi, I-Lan County, NE Taiwan, P. Ng et al., 27 May 1997. PARATYPES: ZRC 1998.948, 3 males (cl 78.8–103.8 mm, pcl 53.1–67.9 mm, cw 40.8–53.4 mm), 1 ovigerous female (pcl 58.2 mm, cw 45.0 mm), Tai-Shi, I-Lan County, NE Taiwan, P. Ng et al., 27 May 1997; ZRC 1999.0540, 1 male (cl 106 mm, pcl 71.1 mm, cw 56.4 mm), Tai-Shi, I- Lan County, NE Taiwan, P. Ng et al., 28 May 1997; ZRC 1998.460, 1 ovigerous female (cl 81.4 mm, pcl 61.9mm, cw 47.7 mm), Tai-Shi, I-Lan County, NE Taiwan, P. Ng et al., 25 May 1998; ZRC 1995.593, 1 male (pcl. 66.7); ZRC 2001.0064, 1 immature female (pcl 44.5 mm, cl 30.5 mm, cw 22.7 mm), Nangfangao, Su-Ao County, NE Taiwan, P. Ng, 5 Nov 2000; MNHN B26321, 1 male (cl 78 mm), 1 ovigerous female (cl 81.0 mm), Tai-Shi, I-Lan County, NE Taiwan, T.- Y. Chan, May 1998.
Other material examined. Philippines: ZRC 2001.0417, 1 immature female (cl 26.4 mm, pcl 18.9 mm, cw 14.6 mm), Balicasag Island, local fisherman with tangle nets, Dec 2000; ZRC 2006.0156, 1 spent female (cl 82.0, pcl 55.7 mm, cw 44.3 mm), Maribohoe Bay, 100–300 m, T. J. Arbasto, Nov 2003 – Apr 2004; ZRC 2001.0581, 1 male (cl 88.7 mm, pcl 57.2 mm, cw 45.0 mm), 1 ovigerous female (cl 93.7 mm, pcl 63.2 mm, cw 51.0 mm), Balicasag Island, 50–500 m, 28 Nov 2001; ZRC 2006.0157, 1 ovigerous female (cl. 85+ mm, pcl 62.7 mm, cw 50.2 mm), 3 females with rhizocephalan (cl 76.5–78.8 mm, pcl 55.5–58.1 mm, cw 44.7–46.2 mm), Balicasag Island, 200-300 m, tangle net, J. Arbasto, 2004–2005. Japan: ZRC 1999.0236, 1 male (pcl 87.3 mm, cl 60.3 mm), off Okinawa, 260–480 m, Okinawa Experimental Fisheries Station, 1960’s. Australia: QM W10596, 1 male (pcl 56.6, cl 35.3 mm), 28°04’S, 153°57’E, 400 m, Iron Summer shot 3, P. Dutton, 28 Jul 1982.
Description. Carapace pyriform, pcl 1.2–1.3 times width. Rostral spines about half pcl; widely separated basally, strongly divergent, curved dorsally; with 2 or 3 ventral (excluding basal) spines; with 1–3 (usually 2) widely spaced spines along proximal half of lateral margin. Orbital margin with 4 or 5 well-spaced spines increasing in size posteriorly: 1 or 2 small preorbital spines at level of rostral base, larger supraorbital, slender intercalated and postorbital spines; with large, hepatic spine anterolaterally directed, with 2 or 3 small accessory spines; dorsal surface covered with short slender, seta-tipped spines, setae often hooked; anterior branchial and cluster of 4 gastric spines markedly longer than surrounding spines; branchial regions widely separate.
Epistome with ventrolaterally directed spine lateral to antennal gland aperture, margin of aperture angular posteriorly, with cluster of 2–4 spines midway between aperture and anterolateral angle of buccal cavity; anterolateral angle of buccal cavity crenulate.
Eyestalk with elongate, stiff setae on anterior margin; interantennular spine bifurcated in distal third or quarter, divergent; distal margin of antennular sinus produced to slender, ventrolaterally directed spine.
Basal antennular article with 2 or 3 ventrally directed spines; basal antennal peduncle article ventrally and distally spinose; penultimate article distally and ventrally spinose; ultimate article unarmed; flagellum extending slightly beyond rostral apices.
Third maxilliped merus as wide as ischium; meral surface spinose, with slender spine on either side of carpal articulation, anterolateral margin with spiniform apex and subdistal inner spine; ischium with dentate margins, surface with conic tubercles; without longitudinal groove.
Third sternite of male with anterior median row of low spines, posteriorly with scattered, low tubercles; surface of remaining sternites spinose. Third sternite of female sparsely granulate.
First pleopod of male (G1) gently curving outwards, with distal tenth distinctly curved; subdistal papilla on inner margin subequal in length to margin between papilla base and pleopod apex, papilla straight, directed perpendicularly to margin; obtuse shoul- der proximal to subdistal papilla.
Male abdomen with 7 distinct somites, though telson and sixth somite only slightly movable; widest at somites 2 and 3; all somites distinctly spinose.
Female abdomen with 7 distinct somites; somites 1–5 with pair of median spines and 1 or 2 sublateral spines; telson granulate; forming ‘operculum’; widest at somite 6.
Chelipeds (P1) dissimilar in adult males and females.
Male chela distinctly inflated, granulate (in most specimens larger than about 50 mm pcl), non-spinous; carpus and merus with row of stout conical spines along lower and inner margins, other surfaces covered with low, well-spaced tubercles; occlusal margins of dactylus and pollex with blunt, obtuse teeth, with distinct gape; cheliped length 1.7–2.9 times pcl; dactylus 0.5–0.6 palm length.
Female 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 1.3 –1.5 postrostral carapace length; dactylus 0.6–0.7 propodus length.
Walking legs (P2–5) long, slender, decreasing in length posteriorly. P2 about 3.2–3.5 times postrostral carapace length in males, 2.2–3.1 in females. Male P2–4 propodus, carpus and merus granular, with short, widely spaced, upright spines; dactyli covered with dense soft setae, lateral margins with row of long, coarse setae, apex corneous, those of P2 and P3 about 0.4–0.5 propodus length, those of P4 and P5 about 0.4–0.5 propodus length; P5 merus 0.7–0.8 times postrostral carapace length. Female P2–4 propodus, carpus and merus granular, and strongly spinous, with longitudinal rows of long, widely spaced, upright spines; along lower and lateral margins; dactylar ornamentation similar to males; dactyli of P2 and P3 about 0.4–0.5 propodus length, those of P4 and P5 about 0.5–0.6 propodus length; P5 merus 0.7–0.8 times pcl.
Etymology. Named maxima (Latin), for its massive size in relation to P. o r y x, with which the new species has been confused. The specific epithet also alludes to the second author’s pet cat, “Maximus”.
Remarks. Pleistacantha maxima sp. nov. has been confused with P. o r y x, which it closely resembles. Previous records of P. o r y x from Australia and Taiwan (Davie & Short 1989; Davie 2002; Ng et al. 2001) in addition to a number of Japanese records (Sakai 1965, 1976; Ikeda 1998) are based on P. m a x i m a. Pleistacantha oryx, a species smaller in size than P. maxima, will be redescribed in a forthcoming study. Both species are distinguished from other congeners by the combination of long rostral spines that exceed half pcl, the shallowly bifurcate interantennular spine that is divided for not more than onethird of its length, and the P5 merus that is shorter than the pcl. The most obvious distinction between P. o r y x and P. maxima is their maximum sizes. Pleistacantha oryx is not known to exceed 32 mm pcl (Sakai 1938), whereas P. maxima reaches at least 71.0 mm pcl. Pleistacantha maxima further differs from P. o r y x in the following features:
— Pleistacantha oryx reaches sexual maturity by about 30 mm pcl. By this size, females are mature and males exhibit marked cheliped inflation. Similarly sized females of P. maxima, however, are sexually immature and females are not known to mature until at least 61.9 mm pcl. Similarly, males do not exhibit marked cheliped inflation below 53.0 mm pcl.
— In P. o r y x, the gastric and branchial spines are relatively short, being shorter than the anterior hepatic spine, and the dorsal surface is covered with small acute granules. In contrast, the gastric and branchial spines in P. maxima are proportionally much longer, being as long as or longer than the anterior hepatic spine and the dorsal surface is covered with numerous spinules, producing a much thornier appearance than in P. o r y x.
— The rostral spines are inclined dorsally in both P. o r y x and P. maxima, but the direction of curvature in lateral view differs between the two species. In P. o r y x, the dorsal margin of the rostral spines is broadly convex. In contrast, the dorsal margin of the rostral spines is concave in P. maxima. The degree of curvature of the rostral spines in P. maxima ranges from weak to marked so that the distal portion may approach near vertical. The degree of rostral curvature in P. maxima is generally size related, being most pronounced in the largest adults.
— The chelae in adult male P. o r y x are more robust than in P. maxima, in which the chelae are more slender. The relative length of the dactylus and palm of the cheliped differs between both sexes of the two species. In P. o r y x, the dactylus is approximately 0.7 times the dorsal palm length, in contrast to 0.5–0.6 in P. maxima.
— The G1 differs between P. o r y x and P. maxima (Figs. 7 E–G, I). In P. o r y x, the apex of the G1 is acute and the margin immediately proximal to the subdistal papilla is distinctly convex. Conversely, in P. maxima, the apex of the G1 is rounded, and the margin immediately proximal to the subdistal papilla is almost straight. Note that the specimen illustrated in Fig. 7 I is the first record of P. o r y x sensu stricto from Taiwan.
— In general, the carapace in P. maxima is proportionally broader than in P. o r y x, as measured by the pcl:cw ratio. The pcl:cw ratio in P. maxima ranges from 1.24–1.34 (mean 1.27, n = 17) for all specimens and 1.24–1.30 (mean 1.27, n = 15) for mature specimens only, in contrast to 1.33–1.43 (mean 1.37, n = 5) for mature P. o r y x examined for this study. The range of carapace proportions may overlap between P. maxima and P. o r y x when specimens of all sizes are considered but in mature specimens, the carapace proportions will distinguish the two species.
Distribution. Sagami Bay and Okinawa, Japan, Taiwan, the Philippines and southeastern Queensland, Australia; 100– 480 m.
description: Published as part of Ahyong, Shane T. & Lee, Timothy, 2006, Two new species of Pleistacantha Miers, 1879 from the Indo-West Pacific region (Crustacea, Decapoda, Majidae), pp. 1-17 in Zootaxa 1378 on pages 9-15, DOI: 10.5281/zenodo.175003