Diplosoma marsupiale, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 276-277

Diplosoma marsupiale n. sp.

( Figs 60 ; 121D )

TYPE MATERIAL. — Philippines. Bohol Sea, Camiguin Island, 9°12.89’N, 124°38.03’E, 4 m, 18.IV.1997 ( MNHN A 2 DIP. A 148).

ETYMOLOGY. — From the Latin marsupium: pouch.

DESCRIPTION

The colonies extend in thin whitish sheets on a sandy bottom. The thin and soft tunic is colourless, most transparent at the edge of the colony and between the groups of zooids. It contains a white pigment around the zooids ( Fig. 121D ). The basal layer includes sediment particles.

Brown pigment cells make a peculiar design in the body wall of the zooids. There are six radiating lines around the base of the oral siphon, a speck with a diffuse outline at the anterior end of the endostyle, and a spot at the anterior edge of the cloacal aperture. In addition, there is a brown pigmentation on the gut and gonads.

The oral siphon has six large, petal-like lobes above a strong sphincter ( Fig. 60A ). The cloacal opening is wide. The branchial sac has 10 elongated stigmata on each side in the first row. The retractor muscle is shorter than the thorax, and issues from the posterior part of the thorax ( Fig. 60A ).

The abdomen is folded under the thorax. The two testis lobes ( Fig. 60B ) are pressed against each other and against the gut loop. The ovary has the usual place against the testis. The eggs remain in the abdomen, and even advanced larvae with a developed tail and buds remain includ- ed in the abdomen against the digestive loop.

The larvae ( Fig. 60C ) measure 0.75 mm for the trunk. They are made opaque by an abundance of round white cells distributed throughout the larval body wall except at the base of the tail and the tip of the adhesive papillae. The adhesive papillae have narrow brown stems. They are encircled by eight or more often 10 short ampullae.

REMARKS

This species has some characters in common with Diplosoma versicolor Monniot F., 1994 : brown pigment, large oral lobes, a retractor muscle, and two testis lobes. It differs in the shape of the colony, and the size and internal structure of the larva.

Figures

FIG. 60. — Diplosoma marsupiale n. sp.; A, thorax; B, abdomen; C, larva. Scale bar: 0.5 mm.

FIG. 121. — A, Polysyncraton aspiculatum Tokioka, 1949; B, Polysyncraton cerebellum n. sp.; C, Polysyncraton thallomorpha Monniot F., 1993;D, Diplosoma marsupiale n. sp.; E, Diplosoma pannosum n. sp.; F, Diplosoma pavonia Monniot C. & Monniot F., 1987.