Polycirrus clavatus

Polycirrus clavatus (Kinberg, 1867)

Fig. 16a–e

Cyaxares clavatus Kinberg, 1867: 348.

Polycirrus clavatus.— Hessle, 1917: 227.

Polycirrus habitats Carrerette & Nogueira, 2013: 166–170, figs 9–10, tables 2, 6. New synonym.

Type locality. Brazil, Alagoas, 9°S.

Material examined. HOLOTYPE: SMNH 993. Brazil, 9° S, 33 m (18 fms), coll. Werngren, 1852.

Description. Holotype poorly preserved with body wall and many chaetae damaged, pale brown in colour, anterior fragment of 9 segments 2 mm long, 0.5 mm wide excluding buccal tentacles, mid-body fragment of 7 segments 2 mm long, 0.5 mm wide, poorly preserved, these 2 fragments may have been connected originally giving a total of 16 segments. Sex unknown.

Dorsum anteriorly smooth. Venter anteriorly with mid-ventral groove and poorly defined ventro-lateral pads; pads more-or-less smooth. Mid-ventral groove from segment 3 (Fig. 16a).

Buccal tentacles of two types, with few remaining attached: (1) cylindrical, thickened distally, distinctly grooved and (2) cylindrical, uniformly thin, weakly grooved, both arising at junction between prostomium and upper lip. Upper lip prominent medial lobe with slight lateral expansions at base forming enclosed diverticulae, margin of medial lobe straight; oral surface glandular and ciliated. Outer lower lip subconical lobe protruding above venter, tessellated (Fig. 16a).

Notochaetigerous segments at least 14, extending to segment 16 (holotype broken after segment 16). Notopodia digitiform, prechaetal lobe low, postchaetal lobe digitiform, longer than prechaetal (Fig. 16b). Notochaetae within a chaetiger consisting of one type (chaetigers 4, 14 examined), gradually elongating from dorsal to ventral, pinnate, posteriorly same form as those anteriorly (Fig. 16c). Neurochaetae beginning on segment 4 or 5 (left-right side variation). Neuropodial tori ridge-like, similar along body. Uncini with moderately long neck and undulating base (Type 2, but see Comments), teeth above main fang arranged in double transverse series (MF:1:7) enlarged median tooth above main fang present, subrostral process absent (Fig. 16d–e).

Nephridial papillae present, globular. Pre-gular membrane nephridial papillae present on segments 3, 4. Postgular membrane nephridial papillae present, extending from segment 5 to 6; situated at ventral base of notopodia (Fig. 16a).

Comments. There is some confusion in the literature on the type locality of P. clavatus. Most authors simply refer it to Brazil, but Carrerette & Nogueira (2013) appear to have introduced the more specific locality of Rio de Janiero. However, the type description clearly states that it was found from latitude 9°S, which puts it in the present State of Alagoas in northeast Brazil. Polycirrus clavatus is very similar to two other species described from Brazil: P. abrolhensis Garraffoni & Costa, 2003 from the Abrolhos Archipelago (18°S) in 10 m of water (see Comments for this species), and P. habitats Carrerette & Nogueira, 2013, collected from off Rio de Janeiro in 720 m. The similarity with the latter species is in fact quite striking, and based on a comparison between the holotype of Cyaxares clavatus Kinberg, 1867 and the comprehensive description of Carrerette & Nogueira (2013) we suggest formal synonymy of the two species. According to Carrerette & Nogueira (2013) P. habitats differs from P. clavatus in having notopodia extending to segment 17 (i.e., 15 pairs) and neuropodia beginning on segment 9 (an additional difference mentioned in their key is the presence of both limbate and pinnate notochaetae in P. clavatus, but present observations indicate that P. clavatus only has pinnate notochaetae like P. habitats). As can be seen in Table 1 the mean variation within a Polycirrus species in terms of number of notopodia is about five segments and for the start of the neuropodia is about four segments, so that P. habitats falls in the range of variation expected for P. clavatus. As there appear to be no other differences between the two species, apart from the uncini (which are taken from different parts of the body and therefore would be expected to be different), we propose that P. habitats should be relegated to a junior synonymy.

The holotype of P. clavatus consists of only 16 segments, so we were unable to observe the uncini of the posterior body. Those of the anterior body (Fig. 16d, e) however are not typical of Type 2 as defined by Glasby & Glasby (2006), which has an elongate rostrum, long neck and arched (concave) base. Nevertheless, the results of their morphometric analysis utilising all components of shape variation placed these uncini in the Type 2 category. It is likely that the uncini of the posterior body have a more typical Type 2 shape. As noted in the section on morphological characters, at least three other species show the combination of Type 2 uncini and early start of uncini occurring on poorly developed neuropodia. In addition, analysis of co-varying notochaetal characters by these authors provided further support for the grouping of this species with other species bearing Type 2 uncini.