Apomatus Philippi, 1844

Kupriyanova, Elena K. & Nishi, Eijiroh, 2010, Serpulidae (Annelida, Polychaeta) from Patton-Murray Seamounts, Gulf of Alaska, North Pacific Ocean, Zootaxa 2665, pp. 51-68 : 54

Genus Apomatus Philippi, 1844

Type-species: Apomatus ampulliferus Philippi, 1844

Generic diagnosis (modified from ten Hove & Kupriyanova 2009).

Tube white, opaque, circular in cross-section, keels and collar-like rings absent. Granular overlay may be present. Operculum a soft membranous vesicle without endplate borne on unmodified pinnulated radiole. Opercular constriction may be present. Pseudoperculum may be present on unmodified radiole. Radioles may be exceptionally flat ribbon-like; arranged in semi-circles (may be up to ¾ of a circle), maximum number up to 40 per lobe in larger species. Inter-radiolar membrane present. Branchial eyes present in the form of ocellar clusters. Stylodes absent. Mouth palps present. Seven thoracic chaetigerous segments. Collar trilobed with smooth margin. Thoracic membrane long, forming ventral apron across anterior abdominal segments. Tonguelets between ventral and lateral collar lobes absent. Collar chaetae limbate, of two sizes, may exceptionally be supplemented by Apomatus chaetae. Apomatus chaetae present in bundles of other thoracic chaetae. Thoracic uncini saw-to-rasp-shaped with approximately 30 teeth in profile, up to 3–6 teeth in a row above and continuing onto peg; anterior peg long, blunt, almost rectangular. Ventral thoracic triangular depression absent. Abdominal chaetae sickle-shaped with finely denticulate blades; uncini rasp-shaped with approximately 30 teeth in profile. Short achaetous anterior abdominal zone present. Posterior capillary chaetae present. Posterior glandular pad present.

Remarks. The controversy whether Apomatus Philippi, 1844 and Protula Risso, 1826 should be regarded as separate genera (ten Hove & Pantus 1985) or synonymized under Protula ( Kupriyanova & Jirkov 1997) has not been resolved yet (ten Hove & Kupriyanova 2009). The genera are separated mainly by the presence ( Apomatus ) or absence ( Protula ) of a soft vesicular operculum on an unmodified radiole, although ten Hove & Pantus (1985) examined operculate and non-operculate forms in the Mediterranean and listed further differences in thoracic blood-vessel patterns, distribution of Apomatus -chaetae, and rows of compound eyes in branchial radioles as differentiating Protula and Apomatus . However, with the exception of the Apomatus chaetae distribution, the characters suggested by ten Hove & Pantus (1985) can be observed only in fresh material and the results are still confusing as significant variability exists. Ben-Eliahu & Fiege (1996: 27) further elucidated the differences between Apomatus and Protula in a key, but none of the studies includes all species of the genera, so a proper revision is much-needed. The new species here clearly belongs to the Apomatus - Protula complex and has been referred to the genus Apomatus because of the distinct soft globular opercula typical for this genus. The generic diagnosis given by ten Hove & Kupriyanova (2009) has been emended here to take into account the features of the new species.