Pyura gangelion

PYURA GANGELION (SAVIGNY, 1816) (Figs 14D, 27A)

Cynthia gangelion Savigny, 1816: 90–147 – Red Sea.

Halocynthia gangelion: Sluiter, 1905: 15 – Djibouti.

Pyura gangelion: Monniot C., 1973: 57 – Red Sea; Monniot F. & Monniot C., 2001: 344, figs 106,108A and 130B.

Pyura (Halocynthia) sansibarica Michaelsen, 1908: 251 – Zanzibar.

Pyura sansibarica: Michaelsen, 1918: 8 – Red Sea; Millar, 1956 – Mozambique; Vasseur, 1969: 926 – Madagascar.

Pyura obesa not Sluiter, 1912; Hartmeyer, 1919: 14 – Western Australia; Kott, 1985: 315 – Australia.

Pyura robusta Hartmeyer, 1922; Kott, 1998: 185 and synonymy – Australia.

Pyura albanyensis Michaelsen, 1927: 193 – Albany; Hartmeyer & Michaelsen, 1928: 435; Monniot C., 1989: 490 – New Caledonia and synonymy; Monniot C. & Monniot F., 1991: 441 – New Caledonia; Monniot F. & Monniot C., 1996: 263 – Papua New Guinea; Kott, 1992: 645 – Australia.

Material

Red Sea, Eilat, coll. ISRSE, 1962.

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

Djibouti, 3–35 m, coll. C. Monniot, 1996.

Description

The mature specimens measure 1.5 cm to 6.5 cm across. They are attached by their ventral side. The largest have epibionts. The thick tunic is reddishbrown, with deep ridges. The youngest specimens have lower protuberances that are more regularly spaced on the sides of the body, and they show double brown lines between the four pale lobes of the siphons (Fig. 14D). The sessile siphons are well apart with obvious spinules. The spinules are dense, about 100 m m in length (Fig. 27A).

The internal anatomy corresponds to the descriptions by Monniot (1973) and Monniot & Monniot (1996). The oral tentacles have few ramifications. The prepharyngeal band has two thick crests. The round dorsal tubercle opens in a C. The branchial sac has six high folds on each side, each with 25 longitudinal vessels, and each fold is separated by three to five vessels. There are parastigmatic vessels.

The gut does not widen much at the stomach. The hepatic gland is made of several lobes. One of the lobes, on the pyloric stomach wall is particularly voluminous, in the shape of a cauliflower, with a green colour that remains in formalin. The gaping anus has a plain edge.

There is one gonad on each side, made of numerous lobes. The left gonad lies in the gut loop.

Endocarps are present above the gonads, along the outer curve of the intestine, and on each side of the heart.

Remarks

This species is widely distributed in the Pacific and Indian Oceans. Among Pyura species with six branchial folds, it is characterized by the disposition of the endocarps and by its siphonal spinules. Its recent collection in the Indian Ocean allows a diverse synonymy to be established here.