Moguai pyriforme, Naruse, Tohru, 2005

Naruse, Tohru, 2005, Species of Moguai Tan and Ng, 1999 (Decapoda: Brachyura: Camptandriidae) from brackish waters in the Ryukyu Islands, Japan, with the description of a new species, Zootaxa 1044, pp. 57-64 : 58-61

Moguai pyriforme sp. nov.

( Figs. 1 a, 2)

Moguai elongatum — Kishino et al., 2001a: 21, pl. 2 (6); 2001b: 129. Moguai sp. — Naruse, 2005 (in press): 207, pl. (Crustacea: lower left).

Material examined. Female holotype. CL 5.0 mm, RUMF­ZC­31, Tima River, Okinawa I., coll. T. Naruse, 8 Dec. 2004.

Paratypes. 1 female, CL 4.1 mm, ZRC 2005.0111, Tima River, Okinawa, coll. T. Naruse, 25 Dec. 2004; 1 ovigerous female, CL 5.5 mm, OMNH­Ar. 4910, Nakaganeku River, Konase, Amami­Oshima I., coll. T. Kishino, 1 May 2000.

Comparative material. Moguai aloutos Tan & Ng, 1999 : male paratype, ZRC 1965.7.9.21, Kuantan, Pahang, Peninsular Malaysia, coll. R. Serène; female paratype, ZRC 1997.0357, Lim Chu Kang mangroves, Singapore, coll. C. G. S. Tan, 6 Mar. 1996; 1 male, 13 females, ZRC 1965.7.15.35–44, Kuantan Pahang, Sep. 1935; 5 males, 5 females, ZRC 2003.0339, mangrove, Pulau Bintan, Indonesia, coll. P. K. L. Ng.

Description of female holotype.

Carapace ( Figs. 1 a, 2a, b) pear­shaped, 1.05–1.12 times longer than broad, dorsal surface uneven, with ridges, protuberances marginally covered with dark, stiff setae, other areas on carapace with fine, soft setae. Epigastric crista present, each mesogastric, cardiac region with a cross­shaped protuberance, mesobranchial region with anterior outer, median protuberances. Frontal region sloped toward midline, outer margin, frontal margin bilobed in dorsal view, frontal width about third fronto­orbital width; supraorbital margin rimmed; infraorbital margin with rounded deep excavation, inner edge of excavation fused with suborbital crista, forming infraorbital cup ( Fig. 2 b); epistome with concave median portion. External orbital angle acute, anterolateral margin without epibranchial tooth, slightly concave, reaching posteriorly about anterior third of carapace, inside lateral wall of epibranchial region; branchial region swollen laterally, posterolateral margin rimmed, rough, continuing from below anterolateral margins to posteriorly produced posterolateral angle.

Third maxilliped ( Fig. 2 c) rectangular, without median hiatus between inner margins when closed; exopod tapered distally, reaching distal outer angle of merus, with distinct flagellum; ischium and merus fused, with suture discernible only along the inner third; carpus triangular, anterior apex positioned (in situ) below inner anterior angle of merus. Chelipeds ( Fig. 2 d) feeble, symmetrical, fingers of chela flat, incurved distally.

Ambulatory legs ( Fig. 2 e) short; meri slightly bent posteriorly, distal posterior angle with blunt projection, dorsal surface with few patches of black, short setae along midline; anterior, posterior margins with long plumose setae; carpi, propodi, dactyli, feeble, dactyli simple, incurved, tip acute, as long as or longer than propodi.

Abdomen ( Fig. 2 f) wide, third to fifth segments fused; first, second segments with transverse ridges along distal margins, fused segments with a medial, pair of lateral transverse ridges on proximal third portion, pair of transverse, one longitudinal ridge on distal half.

Male unknown.

Variations. A female paratype (ZRC 2005.0111) has one small epibranchial tooth behind the external orbital angle and a mesobranchial region that is relatively narrow than in holotype.

Habitat. Moguai pyriforme was collected from brackish water on a pebbly­muddy substratum in riverbeds.

Distribution. Okinawa and Amami­Oshima islands, central Ryukyu Islands, Japan.

Etymology. From the Latin pyriforme meaning “pear­shaped”, alluding to the shape of the carapace. The name is used as a noun.

Remarks. In their revision of Camptandrium Stimpson, 1858 , Tan & Ng (1999) established the genus Moguai for a new species, M. aloutos (type species), and Camptandrium elongatum Rathbun, 1931 . Moguai was distinguished from Camptandrium by the shape of the carapace being longer than broad, the frontal width being a third the fronto­orbital breadth, the presence of an infraorbital cup (a cup­like protuberance on the infraorbital margin), the distal part of the G1 being bifurcated, the ischium of the third maxilliped not fused with the merus, and the inner distal angle of the ischium of the third maxilliped being acutely produced. Moguai pyriforme differs from the diagnoses provided by Tan & Ng (1999) in that it has a relatively broader front, and the merus and ischium of the third maxilliped are fused. Moguai pyriforme , however, possesses all the other characters that are diagnostic of Moguai , there is no doubt about its generic placement even though no males are available for a description of the G1 structure. The generic definition of the genus Moguai , however, will need to be slightly amended to accommodate the characters of M. pyriforme .

Moguai pyriforme can be easily distinguished from M. aloutos and M. elongatum by the proportionately narrower front which is about a third the fronto­orbital breadth (vs. about a half the fronto­orbital breadth), the fusion of the merus and ischium of the third maxilliped (vs. free), and the branchial region being laterally swollen such that the one or two anterolateral teeth are clearly dorsal in position (vs. the branchial region is not distinctly swollen such that the three anterolateral teeth are clearly marginal in position) [cf. Fig. 1 b; Tan & Ng 1999: 203, figs. 3, 4; Rathbun 1931: 95, pl. 13(40–43); Shen 1935: 33, figs. 8C, 10]. The degree of swelling of the mesobranchial region is probably a sexually dimorphic character. A large female of M. aloutos (CL 6.2 mm, ZRC 1965.7.15.35–44), has a relatively more swollen mesobranchial region than males, although this is still much less distinct than that observed on M. pyriforme .

Kishino et al. (2001a, b) recorded M. elongatum from Amami­Oshima. Their specimen (OMNH­Ar. 4910), however, possesses all the diagnostic characters of M. pyriforme [ Kishino, et al., 2001a: pl. 2(6)]; the specimen from Amami­Oshima is not M. elongatum but M. pyriforme .

Figures

FIGURE 1 Moguai pyriforme, sp. nov. and M. elongatum (Rathbun, 1931). a, M. pyriforme, Holotype, female, RUMF­ZC­ 31, CL 5.0 mm; b, M. elongatum, female, RUMF­ZC­ 33, CL 5.1 mm

FIGURE 2 Moguai pyriforme, sp. nov. Holotype, female, RUMF­ZC­ 31, CL 5.0 mm. a, carapace, dorsal view (setae were removed at right half); b, carapace, frontal view; c, third maxilliped, left; d, chela, right; e, third ambulatory leg, left; f, abdomen and telson. Scales, 1 mm.