Polycarpa aurita ( Sluiter, 1890 )

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1199-1200

Polycarpa aurita ( Sluiter, 1890)

Styela aurita Sluiter 1890, p. 338 .

Polycarpa aurita: Kott 1985, p. 152 and synonymy.

Distribution

Previously recorded (see Kott 1985) Western Australia (Cape Jaubert to Cockburn Sound); New South Wales (Port Jackson); Queensland (Moreton Bay, Gladstone, Bowen, Abbot Point, Lizard I. Great Barrier Reef); Northern Territory (Gulf of Carpentaria; Indonesia; Philippines; New Caledonia; Atlantic Ocean (Gulf of Mexico, Caribbean, Venezuela). New record: Western Australia CSIRO SS10/05 (Zuytdorp nr Shark Bay, Stn 110, 26 m QM G328154).

The new record is the first from the Western Australian coast and the only one from the Indian Ocean for this otherwise pan-tropical species.

Description

The newly recorded specimen is about 5 cm long, rectangular and sessile. The test is tough, leathery, wrinkled and warty on the outside. The apertures are sessile and difficult to locate amongst the irregularities of the external test. Dark pigment is in the body wall around the margin of each almost sessile aperture. Internally, the specimen appears to be senescent, with a particularly tough body wall and hard fibrous ligaments joining the branchial sac to the body wall. The four branchial folds on each side are shallow, with internal longitudinal branchial vessels crowded on them. A deep, open, longitudinal reverse S-shaped slit is in the centre of the large, cushion-shaped dorsal tubercle that completely fills the almost fusiform peritubercular area. The gut forms a loop across the posterior end of the body. It is deeply embedded in the body wall and the ligament joining proximal and distal limbs encloses small endocarps in the pole of the loop. Endocarps also are between the limbs of the remainder of the loop. The longitudinal folds lining the stomach can just be seen, through the almost opaque body wall. Gonads are senescent and only traces of their openings can be seen scattered on the body wall amongst degenerate endocarps. The anus is bilabiate and its rim is fringed with small, shallow scallops.

Remarks

Although larger specimens of this species have been reported (to 12.2 cm: Millar 1975), specimens as senescent as this one have not been recorded. Further, it is possible that the present one would have been very much larger when relaxed. It has been assigned to this species on the basis of the almost complete absence of siphonal extensions of the muscular body wall, dark pigment around the margin of each aperture, the deeply incised slit on the large dorsal tubercle that completely fills the peritubercular area, deeply embedded gut, broad stomach with a strong ligature across the distal end of the gut loop, relatively simple gut loop across the posterior end of the body, small endocarps in the gut loop and on the body wall, crowded internal longitudinal vessels on low branchial folds, and tough fibrous connectives between the body wall and the branchial sac.