Pseudopotamilla

Pseudopotamilla sp. cf. P. reniformis (Brugière, 1789)

(Fig. 21 E–G)

Amphitrite reniformis Brugière, 1789: 57.

Pseudopotamilla reniformis.— Bush 1905: 203; Moore 1905: 359; Hartman 1945: 47; Jirkov 2001: 551, figs 1–6.

Potamilla reniformis.—Mclntosh 1922: 232; Fauvel 1927: 309, figs 107a–1; Pettibone 1954: 336, fig. 380u; Day 1967: 764, figs 37.3a–f; 1973: 126; Hartmann-Schröder 1971: 506, figs 174A–H.

Pseudopotamilla sp. A.—Capa 2007: 556–559, figs 11I –P, 12G–J, 13.

Pseudopotamilla sp. B.—Capa 2007: 559–562, figs 12K–N, 14.

Material examined. Queensland, Lizard Island: AM W.41158, AM W.41159, Watsons Bay, 14°39′26′′S, 145°27′03′′E, coral rubble, 4.5 m, 28 Aug 2010; AM W.44368, MI QLD 2406; AM W.44369, AM W.44457, AM W.44458, AM W. 44459, MI QLD 2392.

Description of material examined. Specimens up to 20 mm long, 1 mm wide, 8–12 thoracic and numerous abdominal chaetigers. Pigmentation among specimens varies, with some almost unpigmented, some with base of radiolar crown and anterior chaetigers darkly pigmented, and others with radioles distally pigmented in orange or light brown (Fig. 21 E–G). Radiolar eyes vary from orange to dark purple. Preserved specimens maintain the colour pattern with some purple pigment faded into dark brown (Fig. 21 F–G). Radiolar crown with semicircular lobes and radioles decreasing in length dorsoventrally. Dorsal basal flanges thin, with straight margin, ventral flanges well developed, subquadrangular (Fig. 21 G). Basal membrane reduced. Radioles with smooth margins, flanges absent. Nine to twelve vacuolated cells in cross section supporting radioles basally. Circular compound radiolar eyes in a single row along the outer margin of radioles numbering up to six in some dorsal radioles and decreasing in number to lateral radioles; absent in dorsalmost and ventral ones (Fig. 21 E–G). Dorsal lips with medium length dorsal radiolar appendages. One pair of pinnular appendages shorter than radiolar appendages. Ventral lips and parallel lamellae present; ventral sacs inside the crown. Posterior peristomial collar with dorsal margins fused to faecal groove, with low rounded notches and pockets on each side; lateral margin of collar oblique, increasing in length ventrally to ventral lappets, separated by a short midventral incision (Fig. 21 F–G). Glandular ridge absent on anterior chaetigers. Ventral shields separated from tori by wide gap, with midsegment transverse groove; first one with M-shaped anterior margin (Fig. 21 G). Interramal eyespots absent. Collar chaetae elongate broadly-hooded chaetae. Following thoracic chaetigers with short conical notopodia with superior elongate narrowly-hooded chaetae and inferior paleate chaetae. Thoracic neuropodial uncini avicular, with over 20 rows of small teeth over main fang, occupying more than half its length; narrow breast and long handle. Companion chaetae with asymmetrical hood, with dentate appearance along most of its length. Abdominal chaetigers with slightly elevated neuropodia with broadly-hooded chaetae. Abdominal uncini avicular, with more than 20 rows of small teeth over main fang, number of rows of teeth increase in posterior chaetigers, occupying 3/4 of length of main fang, with narrow breast and short handle. Pygidium bilobed with lateral eyespots on both sides. Tube chitinous with some sand attached at the anterior end in some specimens.

Remarks. Two species of Pseudopotamilla, very similar to P. reniformis, have been described from Australia, Pseudopotamilla sp. A and sp. B, only distinguished by their colour pattern. There is no other evidence to split these specimens until molecular analyses are performed, and differences with the commonly reported P. reniformis, originally described from Iceland but also reported in many biographical regions around the world (e.g., Chughtai & Knight-Jones 1988; Jirkov 2001; Müller 2004; Kolbasova et al. 2014), have yet to be found. Therefore, the species herein is referred to as Pseudopotamilla sp. cf. P. reniformis. Members of this species are distinguished from other Australian congeners in the number and shape of eyes. While P. monoculata has a single ovoid compound eye per radiole, P. reniformis bears several eyes aligned in a longitudinal row, generally more abundant in the more dorsal radioles.

Habitat. Generally associated with hard substrates such as rocks and boulders, but also with coral rubble and dead coral. Appears to be capable of boring into calcium carbonate substrates such as shells, limestone or coral (Chughtai & Knight-Jones 1988; Capa 2007).

Type locality. Iceland.

Distribution. North Atlantic (Eastern European and Mediterranean, American coasts), Arctic (Barents and White Seas), Caribbean, North Pacific (Bering and Japan Seas), Australia (Western Australia, Queensland, New South Wales, Victoria).