Tanaopsis laticaudatus Sars 1882

Tanaopsis laticaudatus (Sars, 1882)

Leptognathia laticaudata Sars, 1886, 353–358, Pl. 15, figs 14–17.

Material examined. 5 females, 3 males (NHM.2008.4805–4812), station RFI 3, 31º53.842’N 034º33.300’E, 57 m depth; 1 female, (NHM.2008.4813), station RFI 7, 31º48.809’N 034º28.892’E, 62 m depth; both 14 September, 2006. 1 female, RFI 2 (TAU AR 28421), 31°53.328’N 034°32.853’E, 58.0 m depth; 1 female, RFI 3(TAU AR 28422); both 0 3 May 2007. 1 female, RFI 2 (NHM.2008.4814), 2 males, RFI 3 (NHM.2008.4815–4816), 1 female, RFI 4, 31°54.193’N 034°33.241’E, 59.0 m depth; 1 male, RFI 5 (TAU AR 28423), 31°53.633’N 034°33.251’E, 55.0 m depth; 3 females, 2 males (TAU AR 28424), RFI 7; all 20 October 2007. All fine mud.

Remarks. Tanaopsis laticaudatus has long been regarded as a junior synonym of T. graciloides (Lilljeborg, 1864), the only taxon in this genus recognized from the north-eastern Atlantic region. In practice, Sars’ material from Italy is the only record in litt. from the Mediterranean: from what has been found recently regarding allopatric and sympatric speciation within Tanaidacea (e.g. Larsen, 2001; Bamber, 2007; Larsen & Shimomura, 2008), it seems highly likely that his species is distinct from the north-east Atlantic T. graciloides. Unfortunately, no comprehensive description, or figure, was given by Lilljeborg, and indeed, the only figure for a Northeast Atlantic-Mediterranean Tanaopsis is that of T. laticaudatus by Sars (loc. cit.; also Sars, 1899, pl. 14).

The present material accords entirely with Sars’ detailed descriptions and figures of T. laticaudatus. Further, the present material, from depths between 55 and 62 m, is all collected from fine mud: recent analysis of extensive T. graciloides material from the Irish Sea (Bamber, in press) found this species to be characteristic only of coarser heterogeneous substrata such as muddy gravel. Until material from nearer Scandinavia is examined and described in detail (a project beyond the scope of the present study) the validity of any synonymy of these two forms cannot be established, so it is considered necessary to distinguish the Mediterranean T. laticaudatus at present.