Apseudes cooperi

Kakui, Keiichi & Angsupanich, Saowapa, 2013, Description of three species of Halmyrapseudes (Crustacea: Tanaidacea: Parapseudidae), with a discussion of biogeography, Zootaxa 3736 (4), pp. 345-367 : 346-347

Identities of Apseudes cooperi and A. digitalis

Apseudes cooperi and A. digitalis have been recorded from river estuaries in southern Africa, with the known distribution of the former lying within the distribution of the latter. Both species have been reported from the Bashee River estuary (Brown 1956). According to Brown (1956), A. digitalis differs from A. cooperi in having a much longer chelipedal dactylus than the fixed finger in male, and a transverse row of plumose setae on pleonites 1–5. The type specimens for the two species have been lost (Elizabeth Hoenson, Iziko Museum, pers. comm.), so we observed four non-type specimens identified by A.C. Brown (one male A. cooperi ; one male and two female A. digitalis ). We found that 1) all four individuals bear a transverse row of plumose setae on pleonites 1–5, and have the inner flagellum of antennule consisting of two articles, and 2) the two males’ chelipeds are similar in shape, with the dactylus slightly longer than the fixed finger. The four specimens share several other character states, including the number of inner proximal simple setae on the pereopod-1 carpus, and the presence of one ventral serrate seta on the propodus of pereopod 6 that is longer than the others. We concluded that A. digitalis is a junior synonym of A. cooperi and belongs in Halmyrapseudes , as previous studies had suggested (Bamber et al. 2002; Guţu 2008).

The male chela of H. digitalis originally illustrated by Brown (1956: fig. B5) is similar to that of adult males in other Halmyrapseudes species; its dactylus is elongate and much longer than the fixed finger, and the bases of the dactylus and fixed finger are well separated. The chelae of the males we observed, however, lack these features but resemble the chelae of subadult male Halmyrapseudes . Brown’s (1956) specimen is ca. 6.1 mm long (measured from his fig. B1), whereas ours are 3.13 mm (SAM A19360.1) and 4.63 mm (A19361.1) long. We thus believe that the two males we observed are subadult specimens that show weaker chela dimorphism than adults, as in other Halmyrapseudes species (Băcescu & Guţu 1974, 1975; Bamber et al. 2002; this study).