Lissoclinum Verrill, 1871

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 282

Genus Lissoclinum Verrill, 1871

Lissoclinum abdominale Monniot F., 1983 ( Figs 65 ; 122C )

Lissoclinum abdominale Monniot F., 1983: 33 , fig. 14. Type locality: Guadeloupe; 1992: 566, New Caledonia.

MATERIAL EXAMINED. — Papua New Guinea. Milne Bay Province, Reef SE of Drawari Island, 10°18.03’S, 151°03.94’E, 16 m, 6. VI.1998 (Sample: CRRF).

DESCRIPTION

As the type of the species is, these colonies are mucous, transparent, and encrust all kinds of substrates ( Fig. 122C ). They disintegrate very easily when touched. The spicules are concentrated in two spots, one at the top of the endostyle and another on the abdomen at its contact with the thorax. The small zooids are colourless, but the spicules give them a spotted white aspect. There are six small oral lobes ( Fig. 65A ). The thorax is about 0.5 mm in length. The cloacal aperture is wide but often narrowed by the thoracic musculature ( Fig. 65A ). There is no cloacal languet. We have not found lateral thoracic organs or a retractor muscle.

The abdomen is folded under the thorax, with the usual shape of the gut loop. The single testis lobe lies in the middle of the gut loop but the ovary protrudes to the side ( Fig. 65A ).

The larvae ( Fig. 65B ) are numerous in the mucous basal layer of the colonies. They have three adhesive papillae on long peduncles and four pairs of digitiform ampullae. There is one bud on each side of the vitellus mass. The larvae are 0.55 mm in length, and the tail is wound in half a turn around the trunk.

The spicules are small balls of numerous needles that are not regularly arranged.

REMARKS

This Atlantic species was collected, too, in New Caledonia (Monniot F. 1992), so its geographical range is wide. It is surprising to find so fragile a species in such far-removed places, but no character or combination of them allows a separation of these Lissoclinum Verrill, 1871 specimens into separate species.

Figures

FIG. 65. — Lissoclinum abdominale Monniot F., 1983; A, zooid; B, larva. Scale bars: A, 0.5 mm; B, 0.25 mm.

FIG. 122. — A, Diplosoma redika Monniot F., 1994; B, Diplosoma versicolor Monniot F., 1994; C, Lissoclinum abdominale Monniot F., 1983; D, Lissoclinum guinense n. sp.; E, Lissoclinum taratara Monniot C. & Monniot F., 1987; F, Lissoclinum textile n. sp.