Diplosoma unitestis Monniot & Monniot 2001, n. sp.

Diplosoma unitestis n. sp. (Fig. 64 A-C) TYPE MATERIAL. — Palau. Koror, West Uchelbeluu Reef, Short Dropoff, cave, 7°15.96’N, 134°31.28’E, 12 m, 28.VIII.1997 (MNHN A 2 DIP. A 157). ETYMOLOGY. — From the Latin unus: one and testis: testis. DESCRIPTION The colonies are very soft cushions about 1 cm thick when fixed. They probably were much inflated in life. They are colourless in formalin with a transparent tunic that allows one to see the zooids and embryos. The zooids have a small oral siphon with six pointed lobes and a large cloacal aperture without a languet, uncovering most of the branchial sac (Fig. 64A). There are eight stigmata per side in the three first rows and six in the last row. There is no retractor muscle. The abdomen is folded under the thorax (Fig. 64A, B). The digestive loop is wide and in its centre is a single spherical testis lobe. At its beginning the sperm duct moves well away from the lobe (Fig. 64A, B) and then it follows the rectum. The ovary is isolated into a pouch of the body wall below the abdomen (Fig. 64A, B). There are several oocytes maturing at the same time. A digitiform vascular appendage protrudes from the centre of the gut loop and penetrates the tunic next to the ovary (Fig. 64A, B). The larvae (Fig. 64C) are incubated in large numbers in the basal layer of the colony, but few have reached full development in our specimen. They have a small size (0.4 mm in diameter) and are not gemmiparous. They have three adhesive papillae and one pair of lateral ampullae on each side. REMARKS Few species of Diplosoma have only one testis follicle. Among them are D. ata Monniot C. & Monniot F., 1987, Diplosoma multipapillata Kott, 1980, D. redika Monniot F., 1994: these have gemmiparous larvae. The European Diplosoma singulare Lafargue, 1968 has more lateral ampullae in the larva. D. handi Eldredge, 1967 and D. hiatti Eldredge, 1967 and Diplosoma siphoniata Romanov, 1977 are not sufficiently described to be compared. Diplosoma versicolor Monniot F., 1994 (Figs 64D; 122B) Diplosoma versicolor Monniot F., 1994: 9, fig. 4. Type locality: New Caledonia. MATERIAL EXAMINED. — Philippines. Bohol Sea, Camiguin Island, 9°12.89’N, 124°38.03’E, 7 m, 18.IV.1997 (MNHN A 2 DIP. A 147). Federated States of Micronesia. Pohnpei, NE lagoon, Tehpehk Island, bath sponge farm growing on nylon line, 6°57.68’N, 158°17.85’E, 15.X.1996 (MNHN A 2 DIP. A 142). DESCRIPTION The colonies of this species are thick, with very few common cloacal openings. The tunic is opaque with a variable design in well-delimited brown and pure white patches (Fig. 122B). The zooids are grouped in cores of tunic in a wide common cloacal cavity. The zooids have a long thorax and a brown body wall.There are at least 10 stigmata in a half row. The retractor muscle is located at the base of the thorax. The large abdomen encloses a voluminous stomach. The testis is usually made of two follicles, but in the same colony there are three testis follicles in some zooids. The larvae are large, round, and deeply coloured (Fig. 64D). The trunk is 1 mm in diameter. The three short and wide adhesive papillae are well-separated. At the base of the papillae, four pairs of club-shaped ampullae are barely visible through the opaque body wall. REMARKS A pontomid shrimp was sheltered in the wide cloacal cavity of one colony. Parasitic copepods inhabit the tunic. This species was described from New Caledonia with the same colony shape and superficial design. The Philippines colonies allow us to describe the larvae of this species, which were absent from the immature New Caledonian specimens.Published as part of Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, pp. 201-383 in Zoosystema 23 (2) on pages 280-281, DOI: 10.5281/zenodo.539144