Pista Malmgren, 1866

Nogueira, João Miguel De Matos, Harris, Leslie, Hutchings, Pat & Fukuda, Marcelo Veronesi, 2011, Four terebellines (Polychaeta, Terebellidae) with problematic taxonomic histories, Zootaxa 2995, pp. 1-26 : 3

Genus Pista Malmgren, 1866

Type species: Amphitrite cristata Müller, 1776 , by original designation.

Diagnosis. Usually two or three pairs of branchiae, on segments 2–3 or 2–4, a few species with a single pair of branchiae on segment 2; branchiae usually with long basal stem. Lobes present on segments 1–4, sometimes also on 1–3 subsequent segments. Usually 17 pairs of notopodia, beginning from segment 4, with broadly winged, distally smooth notochaetae. Neuropodia from segment 5, with long-handled uncini on some anterior segments, frequently until end of notopodia (segment 20), then short-handled until end of body; uncini in double rows on segments 11–20, usually in a completely intercalated arrangement. Nephridial papillae usually on segment 3, dorsal to insertion of lobes on segment 3, genital papillae usually on segments 6–7, located posterior to notopodia and dorsally aligned with them.

Remarks. Pista is a large genus, reported worldwide, characterized by the presence of lobes on anterior segments, long-handled uncini occurring for variable number of segments on the region with biramous parapodia, and 17 pairs of notopodia with broadly winged notochaetae, starting from segment 4.

As discussed by Santos et al. (2010), the morphology of lobes in this group, especially with regard to the shape of lobes on segment 1, is important for distinguishing species. There are two groups of species of Pista , separated by the morphology of lobes on segment 1. One group, which includes the type species P. cristata , has low ventrolateral lobes on segment 1 near the lower lip, not extending anteriorly and not covering the anterior end. The other group, including both species described in this paper, has larger lobes on segment 1 that extend anteriorly and laterally, frequently covering the anterior end, and connected to each other by a lower mid-ventral membrane partially exposing the lower lip.

Other important characters in addition to the morphology of the lobes on segment 1 are uncini shape and the arrangement of nephridial and genital papillae. Smith (1992) discussed intrageneric variation in the morphology of the uncini and the arrangement of nephridial and genital papillae, and Santos et al. (2010) discussed intrageneric morphological variation in other characters within Pista .