Amphitritides sp. 1

Amphitritides Augener, 1922

Amphitritides sp. 1

Voucher. SEA LION: station 40MFB.

Diagnosis. Voucher specimen is a large, robust, complete specimen; about 85mm long and 5mm wide, with 16 thoracic chaetigers with notochaetae and numerous (>200 abdominal uncinigers).

Distal part of prostomium forming conspicuous shelf-like process from which buccal tentacles originate (tentacles mostly missing); basal part of prostomium without eyespots. Peristomium forming lips and continuing laterally from mouth for short extension; upper lip short, hood-like, lower lip narrow.

Segment 1 short, most developed ventrally and ventrolaterally, forming protruding ventral lobe below lower lip. Segments 2–4 with anterior margins thickened, but without lobes. Branchiae present; two pairs on segments 2-3 (left branchia on segment 2 missing); second pair aligned slightly laterally to first pair; first pair about twice as large as the second ones (both shorter than body width); both dichotomously branching with short ramifications; each with short and thick main stem. Nephridial papillae present segments 3 and 6-8; inserted laterally to branchial stem on segment 3 and anteriorly to base of notopodia and aligned to them on segments 6-8.

Notopodia from segment 4, present on 16 segments. Notochaetae arranged in two rows with those in anterior row shorter; notochaetae smooth, subdistally with bi-limbate inflation, inflation expanded basally; distally extending into slender tip. Neuropodia beginning on chaetiger 2 (segment 5), as low rectangular ridges slightly raised from the surface of the body throughout, without internal supporting rods. Uncini short handled, with conspicuous dorsal button, short triangular heel and prow distally pointed and downwardly directed; uncini in double rows, from thoracic unciniger 7 (segment 11) until posterior body (including many abdominal segments, but about posteriormost 1/3 of the body with uncini in single rows again).

Pygidium slightly damaged, not clearly observed. Tube: fine, smooth, muddy; patches of thin sand encrustation on the body observed.

Remarks.  Falkland Island specimen agrees well with genus Amphitritides in having two pairs of small, dichotomously branching branchiae, much shorter than body width, neuropodia as low ridges along whole body, with uncini arranged in double rows from the 7th uncinigerous segment until posterior segments, where in single rows again. Similar genera Neoleprea Hessle, 1917 and Tyira Hutchings, 1997 can be distinguished in that notopodia begin on segment 2 in Tyira, segment 3 in Neoleprea while it is segment 4 in Amphitritides (Nogueira and Hutchings, 2007). The species in genus Amphitritides can be distinguished from each other mainly by the number of pairs of notopodia, morphology of notochaetae and uncini, segments with nephridial papillae and their position. Combination of these characters suggests that Falkland Island specimen represent a new species and should be formally described. The comparison of Falkland Island specimen and six known species of Amphitritides is provided in the table below (see also Nogueira and Hutchings, 2007 for more details).

Comparison of species currently assigned to the genus Amphitritides (modified from Nogueira and Hutchings, 2007).