Paraniphargus Tattersall, 1925

Ariyama, Hiroyuki, 2016, Two new species of eyeless amphipods from a coastal area in Japan (Crustacea: Amphipoda: Hadziidae, Melitidae), with reinstatement of the genus Paraniphargus Tattersall, 1925, Journal of Natural History 50, pp. 2277-2297 : 2287-2289

Genus Paraniphargus Tattersall, 1925

Paraniphargus Tattersall, 1925: 241 ; Barnard and Barnard, 1983: 675, fig. 5, map 54. Melita: Sawicki et al., 2005: 66 (in part) [not Leach, 1814: 403].

Type species

Paraniphargus annandalei Tattersall, 1925 by monotypy.

Emended diagnosis

Head, rostrum weak, eyes absent. Antennae slender; antenna l peduncular article 1 longer than article 3, accessory flagellum 2- or 3-articulated; antenna 2 shorter than 1, flagellum short. Mandibular palp slender, with 3 articles; article 1 short, articles 2 – 3 long, article 3 linear, weakly setose. Lower lip with developed inner lobes. Maxilla 1, inner plate ovate, with 3 – 4 apical setae, not setose medially; outer plate with 6 – 9 robust setae distally; palp 2-articulated, with apical robust setae. Maxilla 2, inner plate without facial or medial setae. Coxae relatively long, coxa 4 lobate. Gnathopod 1 small, subchelate; carpus weakly elongate, unlobed; propodus shorter than carpus, trapezoidal, palm transverse, dactylus fitting palm; no sexual dimorphism. Gnathopod 2 enlarged, subchelate; carpus of medium length, weakly lobate; propodus large, roundish rectangular, palm oblique; dactylus long, curved posteriorly; no sexual dimorphism. Pereopods 3 – 4 slender; bases of pereopods 5 – 7 relatively expanded, slightly lobate posterodistally, posterior margins serrate. Uropods biramous; uropods 1 – 2 rami extending subequally, with robust setae marginally; uropod 3 elongate; peduncle short; parviramous, outer ramus long, 1- articulated, with marginal and terminal setae, inner ramus shorter than 20% length of outer. Telson of ordinary length, fully cleft, lobes tapering, each with 2 apical robust setae.

Remarks

Four species have been described in the genus Paraniphargus : P. annandalei Tattersall, 1925 from a freshwater stream in the Andaman Islands; Paraniphargus ruttneri Schellenberg, 1931 from a freshwater lake in Java; Paraniphargus leleuporum Monod, 1970 from groundwater in the Galapagos Islands; Paraniphargus vermiamicus Bamber, 2003 from marine waters in Hong Kong. Paraniphargus leleuporum was subsequently transferred to a new genus, Galapsiellus Barnard, 1976 by Barnard (1976), and P. vermiamicus was transferred to Tegano Barnard and Karaman, 1982 by Horton and Lowry (2012), leaving only two species in the genus.

Several studies have dealt with the difference between Paraniphargus and the related genus, Melita Leach, 1814. Schellenberg (1931) pointed out that they differ only in the 1- articulated outer ramus of the uropod 3, the lack of the anteroventral cusp on the head, the weak mandibular palp, and the naked medial margin of the inner lobes of both maxillae. Barnard and Barnard (1983) stated that many species of Melita have lost article 2 on the uropod 3 outer ramus, and that Paraniphargus differs from Melita in the loss of eyes and medial maxillary setae. Stock and Ilife (1995) suggested that there were only slight differences between Paraniphargus , Melita and a third genus Josephosella Ruffo, 1985 . More recently, Sawicki et al. (2005) synonymized Paraniphargus with Melita citing a lack of distinction in the setation of maxilla 2 and the number of articles in the uropod 3 outer ramus between these genera. The present study recognizes the sexually monomorphic gnathopod 2 as a distinctive generic character of Paraniphargus separating it from Melita species that have a sexually dimorphic gnathopod 2 ( Barnard and Barnard 1983; Jarrett and Bousfield 1996). Although the original description of P. annandalei and P. ruttneri by Tattersall (1925) and Schellenberg (1931), respectively, do not include details of the presence or absence of sexually dimorphic characters, Barnard (1976) proposed the absence of sexual dimorphism in the gnathopods without stating the basis for this observation. The medial margin of the maxilla 2 inner plate is quite bare of setae in all species of Paraniphargus including P. shiosai sp. nov., whereas in the Melita species, number of setae on the medial margin varies from very many to a few but never without setae. Based on the above characters Paraniphargus is here reinstated as a distinct genus from Melita.

Included taxa

Three species: P. annandalei Tattersall, 1925 ; P. ruttneri Schellenberg, 1931 ; P. shiosai sp. nov.