Polycarpa rigida Herdman 1881

Polycarpa rigida Herdman 1881, p 76; Kott 1985, p 199.

Distribution

Previously recorded (see Kott 1985): Tasmania (Thobin Bay Vansittart I., NW and NE Tasmania, Shouten Passage, Banks Strait, Port Arthur, Port Davey); Victoria (Bass Strait, Cape Howe); New South Wales (Port Jackson). New records: Tasmanian Canyons (Banks Strait, 168 m; Pieman Canyon, 176 m; King I. Canyon, 249 m).

Description

Newly recorded specimens are the usual large (up to 10 cm long) wedge- to crescentshaped individuals, with a concave dorsal surface and the terminal branchial aperture and antero- dorsal atrial opening each on short naked siphons. The remainder of the test is thin, sand filled, but flaccid. The delicate body wall is closely applied to the test. Eight fine branchial tentacles are around the base of the branchial siphon. The dorsal tubercle has a U-shaped slit with the horns turned out. Branchial folds are low and narrow with about 12 internal longitudinal vessels and about eight stigmata per mesh between them and more than twice that number of internal longitudinal vessels on the folds. The gut forms an almost circular arc between the oesophagus and the atrial aperture. The stomach is small, spherical with longitudinal folds. Gonads are senescent in the newly recorded specimens.

Remarks

The species differs from P. chinensis, P. procera, and P. tinctor in its flaccid rather than hard firm test. Polycarpa tinctor has distinctive separate male and female gonads and the other species have hermaphrodite gonads. These are scattered over the body wall in the present species, rather than being arranged in a line on each side of the endostyle (P. procera) or each side of the dorsal lamina (P. chinensis). Records of the present species are from more southerly latitudes than other species of Polycarpa except P. zeteta Millar, 1982 and P. pegasis Michaelsen, 1922.