Lissoclinum bistratum ( Sluiter, 1905 )

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 283

Lissoclinum bistratum ( Sluiter, 1905)

Didemnum bistratum Sluiter, 1905: 103 . Type locality: Somalia.

Lissoclinum bistratum – Monniot F. 1992: 566, New Caledonia.

Lissoclinum voeltzkowi ( Michaelsen, 1920) – Monniot F. & Monniot C. 1996: 175, Palau.

MATERIAL EXAMINED. — Indonesia. Tawata Island, 20 m, coll. Erhardt ( MNHN A2 LIS 160).

Palau. Koror, Ngerchelangael, 7°19.27’N, 134°29.32’E, 10 m, 3.IX.1996 ( MNHN A2 LIS 147).

Tonga. Tongatapu, Tufaka Island, 21°03.83’S, 175°15.42’W, 2 m, 19.XI.1997 ( MNHN A2 LIS 155).

Fiji. Coll. Ireland ( MNHN A2 LIS 113-114).

Yemen. Socotra Island, coll. Monniot ( MNHN A2 LIS 164).

Tanzania. Pemba Island, 5°09.20’S, 39°37.88’E, 10 m, coll. Monniot ( MNHN A2 LIS 143).

Mozambique. Ibo Island, 2-10 m, coll. Monniot ( MNHN A2 LIS 140-142).

Comoros. Mayotte Island, 15 m, coll. Aknin ( MNHN A2 LIS 139).

Madagascar. Nosy-Be, 12-15 m, coll. Laboute ( MNHN A2 LIS 112).

South Africa. KwaZulu Natal, Sodwana Bay, 19 m, coll. Schleyer ( MNHN A2 LIS 136).

REMARKS

Green flat cushions of Lissoclinum colonies, containing abundant symbiotic algae in their common cloacal cavity, have been collected in many stations, as well in the western Pacific Ocean and the Indian Ocean. All colonies have similar zooids and larvae. Differences appear only in the shape and size of spicules. The presence of brown pigment cells in the tunic is variable.

We have examined the type specimens of Lissoclinum bistratum ( Sluiter, 1905) , MNHN A2 LIS 24 and Lissoclinum timorensis ( Sluiter, 1909) ZMA TU 482 and 1274. They differ only in the shape of spicules. Both shapes of spicules, and intermediate ones, were found either in the Pacific or Indian colonies that we studied, sometimes in the same locality. The anatomical characters of all these specimens are constant. In Michaelsen’s (1920) description, L. voeltzkowi differs from L. bistratum in lateral organs protruding into the tunic instead of being internal. But examining the type of L. bistratum , the lateral thoracic organs protrude externally. Michaelsen’s species is said to be brown, Sluiter did not specify the color in life of L. bistratum .

Kott (1998) synonymized L. voeltzkowi with L. timorensis , without any explanation.

Considering the large variability of the spicules in the same geographical area, the absence of distinctive anatomical characters in the zooids and larvae, and the similar structure of the colonies, we propose to gather all the material described as L. voeltzkowi or L. timorensis in a single species L. bistratum ( Sluiter, 1905) which has priority.

Nevertheless, the chemical differences found by chemists in populations of L. bistratum and L. voeltzkowi in New Caledonia remain puzzling, but they may be due to different symbionts.