Bathyarctus rubens ( Alcock & Anderson, 1894 )

Yang, Chien-Hui, Lin, Chia-Wei & Chan, Tin-Yam, 2014, Additional slipper lobsters of the subfamily Scyllarinae Latreille, 1825 (Crustacea, Achelata, Scyllaridae) from Taiwan, Zootaxa 3852 (3), pp. 336-346 : 337

Bathyarctus rubens ( Alcock & Anderson, 1894)

( Figs. 1 , 6A )

Arctus rubens Alcock & Anderson 1894: 165 (type locality: Sri Lanka). Bathyarctus rubens Holthuis 2002: 505 , figs. 1–3.—Chan 2010: 160.

Material examined. Yilan County, Dasi fishing port, commercial trawler, 29 Jul 2011, 1 male 14.9 mm cl ( NTOU M01283 ); 0 8 Aug 2011, 1 male 14.4 mm cl ( NTOU M01284 ).

Diagnosis. Tubercles on surface of carapace small but distinct. Rostral tooth blunt. Pregastric tooth as a transverse carina. Gastric and cardiac teeth elevated and subequal in size. Orbital carina with margin smooth. Posterior margin of carapace with deep medial incision. Abdomen with wide transverse grooves. Articulating surfaces of abdominal tergites without setose grooves. Abdominal tergites II–IV almost smooth on either side of transverse groove. Elevated median carina present on abdominal tergites II–V, that of tergite IV highest. Abdominal pleura II–V rounded distally. Middle of posterior margins distinctly incised at abdominal tergites I–III but produced posteriorly and tooth-like at abdominal tergites IV and V. Anterior margin of antennal segment VI bearing 6 or 7 teeth, tips rounded except innermost tooth. Antennal segment IV bearing distinct additional carina, with 5–10 small teeth on anterior margin and 2 or 3 large teeth on outer margin. Propodus of pereiopods I–IV bearing short setae ventrally. Anterior part of thoracic sternum truncate and flat, not medially sunken. Thoracic sternites I–V bearing large median tubercles.

Coloration. Body generally light brown and scattered with small reddish brown spots. Eyes light brown. Articulating surface of abdominal tergite I bearing a distinct red transverse band. Abdominal somite VI and tailfan mostly whitish. Dorsal carina of abdominal tergite IV pale white. Pereiopods pale yellowish white and covered with brown bands.

Distribution. Indo-West Pacific from Madagascar to Taiwan, Australia, and Fiji; at depths of 183– 732 m.

Remarks. Bathyarctus contains five species and B. rubens is the most widely distributed species in the genus. The present report extends its northernmost record from the Philippines to Taiwan. Previously two Bathyarctus species have already known from Taiwan, namely B. formosanus (Chan & Yu 1992) and B. chani Holthuis, 2002 . Bathyarctus rubens can be readily distinguished from the above two species in having a smaller size, weaker abdominal sculpture, highest median carina on the abdominal somite IV and very different coloration (see Chan & Yu 1992; Holthuis 2002).

Figures

FIGURE 1. Bathyarctus rubens (Alcock & Anderson, 1894), male 14.9 mm cl (NTOU M 01283): A, carapace, dorsal view; B, abdomen, dorsal view; C, abdomen, lateral view; D, thoracic sternum; E, pereiopod I; F, pereiopod II; G, pereiopod III; H, pereiopod IV; I, pereiopod V. All right pereiopods. Scales = 5 mm.

FIGURE 6. A, Bathyarctus rubens (Alcock and Anderson, 1894), male 14.9 mm cl (NTOU M 01283); B, Chelarctus aureus (Holthuis, 1963), female 14.3 mm cl (NTOU M 01288); C, Crenarctus bicuspidatus (De Man, 1905), male 11.8 mm cl (NMMBCD 4007); D, Petrarctus veliger Hothuis, 2002, female 19.4 mm cl (NMMBCD 4008).