Bitias stocki Fransen 1990

Bitias stocki Fransen, 1990

(Figs. 1, 2)

Bitias stocki Fransen 1990: 68, figs. 1–3; Crosnier & Fransen 1994: 50, fig. 3c–e.

Material examined. Southwestern Atlantic Ocean off Brazil: 1 female (pocl 5.3 mm, rl 2.2 mm), TAAF MD 55 / BRÉSIL 1987, off Espírito Santo, eastern slope of Abrolhos Bank, station 43 CB 77, 19º00’S 37º47’W, depth: 790–900 m, 27.V.1987 (MZUSP 31148); 1 ovigerous female (pocl 6.2 mm, rl 2.6 mm), TAAF MD 55 / BRÉSIL 1987, station 43 CB 77, 19º00’S 37º47’W, depth: 790–900 m, 27.V.1987 (MZUSP 31149); 1 male (pocl 6.9 mm, rl 2.9 mm), TAAF MD 55 / BRÉSIL 1987, off Rio de Janeiro, south of Cabo Frio, station 65 CB 106, 23º54’S 42º10’W, depth: 830 m, 02.VI.1987 (MZUSP 31150).

Description. For detailed description and illustrations see Fransen (1990); for illustrations of the Brazilian material see Figs. 1 a–g, 2.

Distribution. Eastern Atlantic: Azores and Cape Verde, 1100–1350 m (Fransen 1990). Western Atlantic: Brazil, off Espírito Santo and Rio de Janeiro, 790–900 m (present study).

Remarks. Bitias stocki was previously known only from the type series: a male holotype and an ovigerous female paratype (allotype) collected at 1320–1350 m south of Pico, Azores, and a female paratype collected at 1100–1300 m southwest of Fogo, Cape Verde (Fransen 1990). The present specimens represent the first record of B. stocki and the genus Bitias from the western Atlantic (Brazil). The Brazilian material agrees well with the type material of B. stocki as described and illustrated by Fransen (1990). The dorsal teeth on the carapace and rostrum are movable (posterior half of the rostrum and carapace posterior to the post-orbital margin) or fixed (distal half of the rostrum); their number ranges from 14 to 16 (Fig. 1 b, f, g). The ventral subdistal tooth may be present or absent and the development of the lateral rostral carina is also variable (Fig. 1 b, f, g).

An important morphological feature of B. stocki not mentioned nor illustrated in the original description of the species (Fransen 1990) is the presence of sharp processes on the abdominal sternum. All three Brazilian specimens have a pair of spine-like processes on the first to fourth abdominal sternites, strongest on the first and diminishing in size towards the fourth; the fifth sternite has a small median process continued by a median carina. At our request, Dr. Charles H.J.M. Fransen examined the holotype of B. stocki (RMNH D 39051), in which he found the same armature on the abdominal sternum. Dr. Fransen’s schematic drawing is reproduced here (Fig. 1 h), thereby completing the description of the holotype. The only other presently known species of Bitias is the Indo-West Pacific Bitias brevis (Rathbun, 1906), which differs from B. stocki in only a few very subtle details (Crosnier & Fransen 1994).