Eudistoma vineum, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 246-247

Eudistoma vineum n. sp.

( Figs 35 ; 117E)

TYPE MATERIAL. — Papua New Guinea. Louisiade Archipelago, Deboyne Islands, Panaete Island, 10°41.72’S, 152°20.13’E, 5 m, 30. V.1998 ( MNHN A3 EUD 227).

ETYMOLOGY. — From the Latin vinum: wine.

DESCRIPTION

The colonies are made of small lobes about 2 cm in height and 1 cm in diameter for the head. The lobes arise from a common base and are sometimes ramified. There are some epibionts on the peduncles but not on the heads which hold the thoraces and abdomens of the zooids. The colony surface is sand-free but there is some sparse sand inside. The colour is wine purple (Fig. 117E) (hence the species name). The most extended zooids are 8 mm long ( Fig. 35A, B ). Both siphons are short with six lobes. No arrangement in systems could be seen. In formalin the dark pigment is mostly present in the upper layer of the tunic and in the upper part of the thoraces.

The strong thoracic musculature is prolonged in two ribbons along the abdomen, at the bottom of which they make little horns. The body is prolonged by a vascular process. The first stigmata row has about 12 stigmata on each side. The abdomen is longer than the thorax. The stomach is posterior. The gut loop is straight and the rectum is not twisted. The gonads are normally placed in the bottom of the gut loop, with many round testis follicles and a central ovary ( Fig. 35B ).

One larva is incubated at a time in the cloacal cavity ( Fig. 35C ). The larval trunk measures 0.85 mm. There are three adhesive papillae in a line and four pairs of flat, stout ampullae, partly bifurcated, the posterior ones ventrally elongated into triangle.

REMARKS

The species has no very distinctive adult character; it is best characterised by the structure of its larva. But the colour of the colonies and their development of ramified lobes, while not distinctive, are nonetheless uncommon.

Eudistoma viride Tokioka, 1955 ( Figs 36 ; 117F)

Eudistoma viridis Tokioka, 1955: 49 , pl. IV, figs 1-5. Type locality: Palau.

Eudistoma viride – Tokioka 1967: 122, Palau. — Millar 1975: 220, fig. 12, Philippines. — Nishikawa 1984: 118, Chuuk, Ponape. — Rho & Huh 1984: 106, pl. 9, figs 1-4, Korea. — Rho & Lee 1989: 65, Korea.

MATERIAL EXAMINED. — Federated States of Micronesia. Chuuk Lagoon, Dublon Island, on mangrove roots, 7°22.90’N, 151°53.55’E, 0.5 m, 9.VII.1992 ( MNHN A3 EUD 136).

Palau. Koror, Ngermerrangel Island, Flatworm , marine lake, 7°19.12’N, 134°30.40’E, 1 m, 4.VII.1994 ( MNHN A3 EUD 135 ) ; Shrimp lake, marine lake on E side Ngerruktabel Island, Ngeremdiu , 7°15.27’N, 134°26.68’E, 1 m, 26.XII.1994 ( MNHN A3 EUD 152 ) .

Fiji. coll. Ireland ( MNHN A3 EUD 92).

DESCRIPTION

The colonies are bushes of small lobes (Fig. 117F). The zooids, arranged in one to three systems per lobe, protrude slightly on round heads. The tunic is translucent. The zooids have a yellow-green pigment in the body wall with a black spot on the neural ganglion and at the top of the endostyle. Both siphons are short. There are six oral lobes and six, sometimes eight, cloacal lobes. There are unperforated areas anteriorly and posteriorly to the branchial sac, which has about 25 stigmata in a half row (but this was difficult to count, the zooids being contracted). There is no narrowing between the thorax and abdomen. The gut loop is long with a posterior smooth-walled stomach in trapezium. The rectum bends at the stomach level even in less contracted zooids ( Fig. 36 ). The gonads lie in the posterior gut loop ( Fig. 36 ).

One to three larvae are incubated in the cloacal cavity. They were not mature in the specimens we examined.

REMARKS

By the shape of the colonies, the pigmentation, and the size of the zooids, this material corresponds well to the original description of the species, and was collected in the same area.

Figures

FIG. 35. — Eudistoma vineum n. sp.; A, B, zooid in two parts; C, larva. Scale bars: A, B, 1 mm; C, 0.5 mm.

FIG. 36. — Eudistoma viride Tokioka, 1955, two zooids. Scale bar: 1 mm.