Crustaenia palawanensis ( Serène, 1971 )

Naruse, Tohru & Ng, Peter K. L., 2007, On A New Species Of Elamenopsis From Singapore, With Notes On Crustaenia Palawanensis (Serène, 1971) (Crustacea: Decapoda: Brachyura: Hymenosomatidae), Raffles Bulletin of Zoology 55 (1), pp. 121-125 : 124-125

Crustaenia palawanensis ( Serène, 1971)

( Fig. 2a )

Neorhynchoplax palawanensis Serène, 1971: 904 , Pl. I(B); Yang, 1979: 12.

Elamenopsis palawanensis – Lucas, 1980: 191; Chuang & Ng, 1994: 87.

Crustaenia palawanensis – Ng & Chuang, 1996: 19, Fig. 6; Guinot & Richer de Forges, 1997: 465.

Material examined. – One male, CL 3.2 mm, CW 2.5 mm, ZRC 1969.12.11.1 (holotype), Quezon, Palawan, Philippines, coll. R. Serène, 21 Jun.1963; 1 female, CL 3.1 mm, CW 2.7 mm, ZRC 1969.12 .11.2 (paratype), data same as holotype ; 1 female, CL 2.9 mm, CW 2.6 mm, ZRC 1965.10 .19.94, off Raffles Lighthouse, Singapore, coll. Jul.1937 ; 1 female, CL 3.0 mm, CW 2.5 mm, ZRC 1992.5946 , Pulau Semakau , Singapore, coll. Reef Ecology Survey Team, 27 Jan.1992 ; 2 females, CL 3.6, 3.9 mm, CW 3.0, 3.4 mm, ZRC 1993.6495 – 6496 , Siloso beach, Sentosa, Singapore, coll. P. K. L. Ng, 1985 ; 2 females, CL 3.3, 4.1 mm, CW 2.8, 3.6 mm, ZRC 2006.0149 , Terumbu Bayan , Pulau Ubin, Singapore, coll. Z. Jaafar et al., Apr.2006 .

Diagnosis. – Carapace oval, longer than broad, dorsal surface surrounded by rim, posterolateral tooth placed on rim. Rostrum separated from carapace by shallow groove, trilobate; each lobe elliptical, lined with dense, hook-shaped setae. Ambulatory legs strongly flattened laterally, ribbonlike. A distinct pair of lobes on segment one of both male and female abdomens; segment 3–5 and telson of male abdomen fused, with remnants of suture between 5 and telson visible; segment 2–5 of female abdomen fused with no distinct sutures. Females with brood cavity.

Remarks. – Crustaenia palawanensis has thus far, only been reported from Palawan ( Philippines) and Singapore. Serène (1971) and Ng & Chuang (1996) described the species, but they did not mention the presence of a posterolateral tooth on the carapace ( Fig. 2a ). This spiniform tooth is anteriorly directed and upturned, and is positioned on the dorsal rim above the base of the first ambulatory leg. Ng & Chuang (1996) regards Neorhynchoplax as the genus closest to Crustaenia in morphology and 14 of the 28 known Neorhynchoplax species also possess a similar posterolateral tooth. The posterolateral tooth of Neorhychoplax species, however, grows not from the dorsal rim of the carapace but from the side wall (see Alcock & McArdle, 1902; Kemp, 1917; Chopra & Das, 1930; Shen, 1932; Pretzmann, 1975; Lucas & Davie, 1982; Nakasone & Takeda, 1994; Davie & Richer de Forges, 1996; present study: Fig. 2b, c ). The form and position of the posterolateral tooth is thus another character that can be used to separate Crustaenia from Neorhynchoplax at the generic level.

Comparative material. – Neorynchoplax euryrostris Davie & Richer de Forges, 1996: 1 female, CL 2.8 mm, CW 3.0 mm, ZRC 2006.0082 , Dumbéa Estuary, New Caledonia, coll. Thollot, 24 Aug.1993; 1 male, CL 2.7 mm, CW 2.8 mm, ZRC 2006.0083 , brackish water in Canara River , New Caledonia, coll. B. Richer de Forges, 12 Nov.1992 .

Neorynchoplax dentata Ng & Chuang, 1996: 1 male, CL 5.6 mm, CW 5.8 mm, ZRC 1994.4284 (holotype), Sungai Pahlawan , tidal freshwater stream in sago plantation, on road from Mukoh to Dalat, Sarawak, Malaysia, Borneo, coll. T. H. T. Tan & M. Kottelat, 15 Jun.1994.

Neorynchoplax mangalis ( Ng, 1988) : 1 male, CL 3.9 mm, CW 3.9 mm, ZRC 1993.6556 (holotype), Mandai mangrove swamp, Singapore, coll. H. K. Tan, 1 Dec.1983 .

Neorynchoplax okinawaensis (Nakasone & Takeda, 1994) : 3 females, CL 2.7–2.8 mm, CW 2.7–2.8 mm, ZRC 2006.0152 , Ibaruma , Ishigaki Island , Ryukyu Islands, Japan, coll. T. Kurihara, 9 Jun.1998 .

Neorynchoplax prima Ng & Chuang, 1996: 1 male, CL 6.7 mm, CW 5.9 mm, ZRC 1994.4233 (holotype), Pengudong , Pulau Bintan, Riau Archipelago, Indonesia, coll. T. Tan, N. Sivasothi, et al., 13 May.1993.

Neorynchoplax sinensis ( Shen, 1932) : 1 male, CL 2.6 mm, CW 2.6 mm, ZRC 1999.0017 , Gu-Lang-Yu, Xiamen, Fujian, China, coll. S.-H. Fang, 13 Dec.1984 ; 1 male, CL 2.6 mm, CW 2.6 mm, 1 female, CL 2.1 mm, CW 2.2 mm, ZRC 1999.0018 , Gu-Lang-Yu, Xiamen, Fujian, China, coll. S.-H. Fang, 10 Sep. 1984 .

Figures

Fig. 2. Posterolateral tooth of Crustaenia Ng & Chuang, 1996, and Neorhynchoplax Sakai, 1938: a, Crustaenia palawanensis (Serène, 1971) (paratype, ZRC 1969.12.11.2); b, Neorhynchoplax mangalis (Ng, 1988) (holotype, ZRC 1993.6556); c, Neorhynchoplax prima Ng & Chuang, 1996 (holotype, ZRC 1994.4233). Scale bars = 1.0 mm.