Lucascinus coralicola (Rathbun, 1909) Rathbun, 1909

Poore, Gary C. B., Guinot, Danièle, Komai, Tomoyuki & Naruse, Tohru, 2016, Reappraisal of species attributed to Halicarcinus White, 1846 (Crustacea: Decapoda: Brachyura: Hymenosomatidae) with diagnosis of four new genera and one new species from New Ireland, Papua New Guinea, Zootaxa 4093 (4), pp. 480-514 : 504-506

Lucascinus coralicola (Rathbun, 1909) n. comb.

( Fig. 10 a–g)

Rhynchoplax coralicola Rathbun, 1909: 108 . — Tesch 1918: 17, 19. — Sakai 1934: 289. — Sakai 1938: 199. — Sakai 1965: 63, pl. 25 fig. 4. — Sakai 1976: 149, fig. 78 (English text), 93 (Japanese text), pl. 46 fig. 4. –– Miyake 1983: 192. Halicarcinus coralicola— Chuang & Ng 1994: 87, 89. — Ng & Chuang 1996: 44–48, figs 17, 18 (for extensive synonymy). — Ng & Jeng 1999: 532. — Ng et al. 2001: 15.

? Halicarcinus septentrionalis Yokoya, 1928: 762 , fig. 2 (see remarks below).

Material examined. Japan. Chiba Prefecture, Okinoshima, Tateyama, intertidal, 15 July 1996, coll. T. Komai, CBM-ZC 3632 (1 male, 4.7 mm). Ryukyu Is., Okinawa I., Minatogawa, Urasoe, RUMF-ZC-1882 (1 male, 3.4 mm); Nago Fishing Port, RUMF-ZC-1883 (4 males, 2.5– 3.9 mm; 1 female, 2.3 mm; 1 ovigerous female, 3.7 mm); Nago Fishing Port, 2–3 m, 11 March 2010, CBM-ZC 13123 (3 males, 2.3–2.8 mm; 2 ovigerous females, 2.3, 2.8 mm). Singapore. Labrador Beach, ZRC 1993.78–91 (8 males, 6 females); Changi, 1°20.5' N, 104°E, MNHN IU- 2014-7145 (B21779), (1 ovigerous female, 1.9 mm).

Diagnosis. Carapace 1.0–1.1 times as long as wide in both male, female. Rostrum tapering, upturned, rod-like, 0.35–0.46 carapace length in male, 0.25–0.3 in female; apex with long setae. Supraocular eave arching, narrow, defined anteriorly by substantial anteriorly directed upturned pseudorostral tooth; postocular margin defined by anterior margin of subhepatic region, produced into a minute tubercle, without notch separating it from supraocular eave. Subhepatic region armed with 2 prominent, triangular, vertically compressed teeth partially or entirely visible in dorsal view. Antennule with broad basal article, produced laterally; interantennular proepistome distinct, ridgelike, fused to epistome. Male cheliped propodus about 6 times as long as depth at base of fingers, upper margin strongly convex along length of fixed finger; cutting edge of fixed finger with blunt proximal tooth, deeply concave over middle half, straight distally; dactylus 0.3 length of palm, cutting edge with blunt proximal tooth, straight or concave distally. Pereopodal dactyli with erect teeth along middle half of length. Male gonopod 1 with swollen base, tapering distal part about as long as length of base. Male gonopod 2 small, tapering to truncate apex, somewhat twisted, with sharp crest-like longitudinal carina.

c b e d

a, c-e a

f, g, h Distribution. Japan (Honshu to Ryukyu Islands), Taiwan, Peninsular Malaysia, Singapore; intertidal to shallow subtidal (2–3 m).

Remarks. Ng & Chuang (1996) redescribed and figured this species (as Halicarcinus ) on the basis of material from Singapore, Peninsular Malaysia and Japan (including Honshu, Ryukyu Islands and Ogasawara Islands). They followed Sakai (1965) and considered Halicarcinus septentrionalis Yokoya, 1928 (type locality, Mutsu Bay, northern Japan), as a junior synonym of Lucascinus coralicola (type locality, Singapore). Nevertheless, these authors noted differences between the populations of L. coralicola in Singapore and in Japan, providing illustrations separately for the specimens from Singapore (Ng & Chuang 1996: fig. 17) and those from Japan (Sagami Bay and Ishikawa Prefecture, Sea of Japan side) (Ng & Chuang 1996: fig. 18). We examined Japanese material from Chiba Prefecture, central Japan, and the Ryukyu Islands, and found that the specimens from the Ryukyu Islands agree well with the description and illustrations of the Singapore specimens. The male specimen from Chiba Prefecture differs from those from the Ryukyu Islands in the wider carapace with more inflated branchiostegal regions, better developed lateral teeth of the rostrum, two subhepatic teeth of the carapace, gonopod 1 with less angular proximolateral margin, and more numerous setae on the distomesial margin extending onto the midlength. In these regards, the specimen agrees rather well with the illustrations of Ng & Chuang (1996: fig. 18). It is thus likely that the Japanese main island (Honshu) population might be specifically distinct, and if so, Yokoya’s (1928) name should be revived. A final conclusion will be reached after examination of more material from the main islands of Japan (Honshu, Shikoku and Kyushu).

We illustrate again the dorsal carapace and male cheliped, and the thoracic sternum with short pleonal cavity for the first time, from the specimen from Chiba Prefecture (CBM-ZC 3632).

Figures

FIGURE 10. Lucascinus coralicola (Rathbun, 1909). Male, 4.7 mm, CBM-ZC 3632: a, carapace, dorsal view, b, frontal region, ventral view; c, thoracic sternum; d, left cheliped, upper view; e, chela, lateral view; f, gonopod 2, outer (ventral) view; g, same, inner (dorsal) view. Lucascinus keijibabai (Takeda & Miyake, 1971). Male, ZLKU 13089 (holotype, male, 2.1 mm: h, frontal region, ventral view. Scale bars a – e, h = 1 mm; f, g = 0.5 mm.