Britorchestia, Bopiah, Arundathi, 2012

Bopiah, Arundathi, 2012, Britorchestia, a new talitrid genus from western Europe and the Mediterranean Sea and a revision of Pseudorchestoidea and Sardorchestia (Crustacea, Amphipoda, Talitridae), Zootaxa 3451, pp. 60-67 : 61-64

Britorchestia gen. nov.

( Figs 1 , 2 )

Type species. Talorchestia brito Stebbing, 1891 .

Included species. Sandhoppers. Britorchestia includes 2 species: B. brito ( Stebbing, 1891) ; B. ugolinii ( Bellan-Santini & Ruffo, 1991) .

Etymology. Named for the type species ‘ T. brito ’ in combination with the Orchestia stem.

Diagnostic description (based on male). Eyes large (greater than 1/3 head length). Antenna 1 short, not longer than article 4 of antenna 2 peduncle. Antenna 2 peduncular articles well developed, slender; peduncular article 3 without ventral process. Labrum without robust setae. Mandible left lacinia mobilis 5-dentate. Maxilliped palp article 2 distomedial lobe well developed; article 4 fused to article 3. Gnathopod 1 parachelate; posterior margin of carpus and propodus each with lobe covered in palmate setae. Gnathopod 2 subchelate; merus and carpus free; dactylus not modified distally. Pereopods 3–7 cuspidactylate. Pereopods 5–7 without setae along posterior margin of the dactylus. Pereopods 6–7 not sexually dimorphic, without row of short setae along posterior margin of dactyli. Pleonites 1–3 without dorsal spines. Pleopods all well developed. Epimera without vertical slits. Uropod 1 rami without apical separ-shaped setae; outer ramus slender; with marginal robust setae. Uropod 3 well developed; ramus subequal or slightly shorter in length to peduncle. Telson entire, with 3–6 robust setae per lobe.

Remarks. Britorchestia brito ( Stebbing, 1891) was originally described from North Devon, England in the genus Talorchestia and subsequently transferred to Pseudorchestoidea by Bousfield (1982). It is a widespread species known from Poland in the Baltic Sea to the Mediterranean and along the Atlantic coast in Morocco. Britorchestia ugolinii ( Bellan-Santini & Ruffo, 1991) was originally described from Corsica in the Mediterranean Sea in the genus Talorchestia and is currently confined to records in the Mediterranean Sea. The main generic-level character differences that excludes these taxa from either Pseudorchestoidea or Talorchestia are: the presence of marginal robust setae on the outer ramus of uropod 1 in Britorchestia (absent in Pseudorchestoidea and Talorchestia ) and the sparse number of telsonic setae (3–6) in Britorchestia (at least 10 in Talorchestia ).

Britorchestia appears to be more similar to Africorchestia Lowry & Coleman, 2011 , Americorchestia Bousfield, 1991 and Sinorchestia Miyamoto & Morino, 1999 . It differs from Africorchestia in the non-sexually dimorphic pereopod 6, in the absence of setae on the posterior margin of the dactyli of pereopod 6–7 and in the smooth dorsum of the pleonites. Britorchestia appears to be the immediate sister taxon of Americorchestia and differs from that taxon mainly in the less well developed eyes and in the length of the uropod 3 ramus. Britorchestia also appears to be similar to Sinorchestia . The main generic-level difference is the ventral plate on peduncular article 3 of antenna 2.

Distribution. Eastern Atlantic: Norway, England, Ireland, Denmark, Holland, France, Morocco. Mediterranean Sea: Corsica, France, Tunisia.

Figures

FIGURE 1. Britorchestia brito (Stebbing, 1891), male, female, Tunisia, Mediterranean Sea (after Bellan-Santini & Krapp- Schickel 1993).

FIGURE 2. Britorchestia ugolinii (Bellan-Santini & Ruffo, 1991), male, female, Tunisia, Mediterranean Sea (after Bellan- Santini & Krapp-Schickel 1993).