Polycarpa nigricans, HELLER (1878)

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 86-87

POLYCARPA NIGRICANS HELLER (1878) ( Fig. 17 )

Polycarpa nigricans Heller, 1878: 174 , fig. 8 – Mauritius; Hartmeyer, 1905: 390, pl. 1, figs 1,2,14; Vasseur, 1967: 115, pl. 5, figs 37–40 – Mauritius; Monniot F. & Monniot C., 1999: 31 – Tanzania.

Not Polyandrocarpa nigricans: Tokioka, 1970: 91 , fig. 5 – Philippines = Polycarpa tokiokai Monniot F. & Monniot C., 1996 .

Not Polycarpa nigricans: Kott, 1985 ; Monniot C., 1987; Monniot C & Monniot F., 1989 = Polycarpa tokiokai .

Material

Mozambique: Ibo Island, coll. C. Monniot, 1995.

Description

The individuals are either isolated or aggregated into plaques that are more or less united by the tunic at their base. In life they are brick-red with darker areas, almost black at the base of the body. The internal side of the tunic has the same colouration but paler. The specimens are often covered with varied epibionts. When fixed in formalin, the tunic becomes darkbrown, almost black. Even when individuals are strongly pressed against each other, they can be separated, and debris gets lodged between the tunics. Traces of regeneration were not found, and so this species is placed in the genus Polycarpa .

The tunic is soft, the internal side somewhat gelatinous. The body wall is opaque, dark-brown, with whitish granules on its internal side; these granules are more or less abundant according to the individual, but sometimes virtually absent. They are denser around the dorsal tubercle, and on the gonads and gut.

The oral tentacles, 25–40 in three orders, may be missing in some parts of some oral siphons. The prepharyngeal band has two thick crests, and is deeply indented dorsally. The dorsal tubercle does not occupy the whole peri-tubercular area; its opening is generally U-shaped, but sometimes a little ramified. The dorsal lamina, smooth and low, begins after a short groove. The branchial sac has four low folds. There are no grouped vessels between the dorsal lamina and the first right fold.

Two branchial formulae:

Figures

Figure 17. Polycarpa nigricans: A, specimen with gonads protruding into the cloacal cavity. B, specimen with gonads included in the body wall. C, detail of a polycarp. Scale bars: A,B = 5 mm, C = 0.5 mm.