Trididemnum cyclops Michaelsen, 1921

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 262-263

Trididemnum cyclops Michaelsen, 1921

Trididemnum cyclops Michaelsen, 1921: 19 . Type locality: Madagascar. — Monniot F. & Monniot C. 1996: 149, western Pacific, and synonymy.

MATERIAL EXAMINED. — Palau. KB Channel, Airai seagrass bed, 7°19.35’N, 134°31.73’E, 0.5 m, 20. VI.1996 ( MNHN A2 TRI 133).

Trididemnum discrepans ( Sluiter, 1909) ( Fig. 48 )

Leptoclinum discrepans Sluiter, 1909: 77 . Type locality: Indonesia. Synonymy: see Monniot F. 1990a: 520, fig. 2.

MATERIAL EXAMINED. — Tonga. Vava’u, Vaipua Inlet, 18°37.92’S, 173°58.79’W, 1 m, 14.XI.1997 ( MNHN A2 TRI 148).

Philippines. Palawan, Honda Bay, 9°55.87’N, 118°55.02’E, 20 m, 24.XI.1997 ( MNHN A2 TRI 119).

DESCRIPTION

This species forms colonies that break up into aggregations of small lobes. The size of each lobe is 5-6 mm in diameter and 3-5 mm in thickness. The very soft gelatinous cushions are black with a translucent tunic. There are no spicules in the upper layer and they are rare in the basal parts, where they are mixed with faecal pellets. The siphons are short. There is a particularly large unperforated area between the oral tentacles and the branchial sac ( Fig. 48A ). The stigmata are numerous, up to 14 in the first half row, but fewer posteriorly. The waist is very long and the retractor muscle extends from it. The gut loop is wide and flat. The single testis lobe lies in its middle, covered by five to six coils of the sperm duct ( Fig. 48A ). The ovary lies against the testis.

The larvae ( Fig. 48B ) are large, 1.3 mm for the trunk. The tail is wound in a half turn around the trunk. The three adhesive papillae have long stalks. On each side are six digitiform ampullae. The larvae are not gemmiparous.

REMARKS

This species is characterised by the small joined lobes of the colony, the colony’s black colour, and the absence of spicules from almost all the tunic, as well as by the numerous stigmata in the zooid and the larval structure. It is a species of very shallow water found in Indonesia, Australia, New Caledonia, Fiji, and now Tonga.

Figures

FIG. 48. — Trididemnum discrepans (Sluiter, 1909); A, zooid; B, larva. Scale bar: 0.5 mm.