Polycarpa reviviscens n. sp.

(Figs 95; 129A)

Polycarpa papillata – Monniot C. 1987b: 299, fig. 10, shallowest form. — Monniot F. & Monniot C. 1996: 252, pl. 9D.

TYPE MATERIAL. — Papua New Guinea. Louisiades, Calvados Island, Brooker Channel, overhang, 11°03.09’S, 152°28.62’E, 7 m, 1. VI.1998 (MNHN S1 POL.B 406).

ETYMOLOGY. — From the Latin revivisco: to be live again.

MATERIAL EXAMINED. — Papua New Guinea. Milne Bay Province, N side of East Cape, Hiliwau, wall, 10°15.65’S, 150°42.75’E, 10 m, 28. V.1998 (MNHN S1 POL.B 407).

Solomon Islands. Santa Cruz Islands, Vanikoro, 33 m, 25.III.1998, coll. Erhardt (MNHN S1 POL.B 419).

DESCRIPTION

The individuals, 2 to 3 cm high and 1 cm in diameter, are erect, grouped in clumps (Fig. 129A). The tunic is clean except at the base, where it forms a kind of peduncle that carries some epibionts. The colour is pale yellow with a pink tint at the siphonal rims. The siphons have four lobes.

The body wall is yellowish and opaque. It penetrates into the basal peduncle in a thick, dense, and vascularised extension.

The oral tentacles, about twenty, are in three orders, with minute ones between them. The prepharyngeal band has two blades, with undulations around the top of the folds and a deep dorsal V. The dorsal tubercle is not protruding; its aperture is a variable sinuous slit.

The dorsal lamina is long with a smooth edge. The branchial sac has four high folds on each side which do not overlap each other. There are eight to 11 vessels on the folds and two to four vessels between the folds. Parastigmatic vessels are present.

The gut forms a simple loop (Fig. 95). Entirely enclosed in a large mesenteron, the stomach has low longitudinal ridges and a small, curved caecum. The straight rectum ends in numerous finger-like anal lobes (Fig. 95).

The gonads are elongate polycarps (Fig. 95). We usually counted three or more polycarps in the middle of the left side of the body and an average of 14 polycarps scattered on the right side. The endocarps are distributed over the whole internal side of the body wall; those anterior to the gut are longer (Fig. 95). There is a thin cloacal velum covered with numerous thread-like papillae.

REMARKS

This new species has probably been confused several time with P. papillata (Sluiter, 1885) and P. captiosa (Sluiter, 1885), with which it shares many characters. The differences include the size of the individuals (smaller here), the structure and colour of the tunic surface, the assemblage of individuals in clumps, and the posterior fleshy prolongation of the body wall.