Proscoloplos cygnochaetus Day 1954

Proscoloplos cygnochaetus Day, 1954

Figure 58

Proscoloplos cygnochaetus Day, 1954: 21, Fig. 3 a–f; 1967: 538, fig. 23.1 E–G; Meyer et al. 2008: 879 –889, fig. 1.

Proscoloplos confusus Hartmann-Schröder, 1962b:133 –134, figs. 161–162; Rozbaczylo 1985:131. Proscoloplos bondi Kelaher & Rouse, 2003: 909 –917.

Material examined. Juan Fernandez Islands, Anton Bruun Cruise 12, Sta. 65-240, 24– 27 m, (1, USNM 60646).— Juan Fernandez Islands, Chile Bay, behind Punta Suroeste, Anton Bruun Cruise 12, Sta. 134, shallow subtidal (1, USNM 65240). — Argentina, Golfo San Matías, IBM Sta. SAO V-201 (1, USNM 1407115); Sta. SAO V-236 (1, USNM 1407116).

Description. A small species, present specimens 3.5 mm long and 0.35 mm wide for up to 40 setigerous segments. Color in alcohol: opaque white. Body cylindrical throughout, slightly expanded in anterior setigers. Prostomium short, smoothly rounded on anterior margin; no eyespots; peristomium with two achaetous rings (Fig. 58 A–B). Anterior parapodia all similar; thoracic and abdominal region demarcated by reduction of neuropodial lobes and appearance of neuropodial swan hooks on setiger 7–9. Branchiae from setigers 5–6 (Fig. 58 A–B). Body narrowing posteriorly; pygidium with two dorsal and two ventral cirri (Fig. 58 C).

Notopodia of anterior and posterior setigers simple, with cirriform postsetal lobes (Fig. 58 D). Notosetae all crenulated capillaries; neurosetae of first 6–8 setigers all capillaries; two neuropodial swan hooks present from setiger 7–9 (Fig. 58 E); superior hook accompanied by 2–3 delicate capillaries; superior hook distinctly larger than inferior hook and with more prominent apical teeth; hooks with large main fang surmounted by 3–5 apical teeth (Fig. 58 E–F); shaft of both hooks bent, with swelling at point of bend.

Branchiae from setiger 5–6, continuing to near posterior end of body; each branchia short, stubby, with several internal bacillary glands (Fig. 58 B).

Remarks. The form of the neuropodial swan hooks readily differentiate this species from all other orbiniids from the area of study. These setae resemble long handled uncini found in other families, not known from any other orbiniid.

Three species of Proscoloplos have been described: P. cygnochaetus from Tristan de Cunha and South Africa by Day (1954, 1967), P. confusus from Chile by Hartmann-Schröder (1962b), and P. bondi from near Sydney, Australia by Kelaher & Rouse (2003). All three species are similar morphologically with the main characters used to separate them being minor differences in the form of the swan hooks and the segmental occurrence of branchiae and hooks. Kelaher & Rouse (2003) examined hundreds of specimens of their P. bondi as part of year-long collections and did not find any evidence of gametes. These authors did, however, find evidence of asexual reproduction and regeneration. Meyer et al. (2008) identified specimens of Proscoloplos from the French Atlantic coast and initiated a study to compare morphology using SEM and molecular markers ITS1 and ITS2 of specimens from France, South Africa, and Australia; SEM was used for a paratype of P. confusus from Chile. No characters were identified to support three species and the molecular results did not result in any clades separating the three widespread populations that would support the retention of three distinct species. Meyer et al. (2008) therefore suggested that both P. confusus and P. bondi were synonyms of P. cygnochaetus. These authors also found no evidence of gametes in any materials examined but did find regenerating specimens in the French populations. Habitats recorded for the species in Australia and France included turf algae. Hartmann-Schroder (1962b) also reported P. confusus from intertidal algae. In order to account for the widespread distribution of P. cygnochaetus Meyer et al. (2008) suggested that algal growth on the hulls of ships could provide a comparable habitat to support short or long-distance transport.

The specimens examined here exhibited branchiae from setigers 5–6 and swan hooks from setigers 7–9 which is within the range of variability reported by Kelaher & Rouse (2003) and Meyer et al. (2008). I conclude therefore, that Chilean specimens described as P. confusus are in fact synonymous with P. cygnochaetus.

Distribution. Chilean coast, intertidal with algae; off the Chilean coast and Juan Fernandez Islands, shallow subtidal, 27 m; Argentina, subtidal. Also from NSW Australia, South Africa, and the French coast in intertidal to shallow subtidal habitats associated with algae.