Ascidia ornata, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 306-307

Ascidia ornata n. sp.

( Figs 81 ; 125E )

TYPE MATERIAL. — Philippines. Bohol Sea, Balicasag Island, SW of Bohol, 9°31.26’N, 123°41.05’E, 13 m, 16.IV.1997 ( MNHN P5 ASC.A 298).

ETYMOLOGY. — From the Latin ornatus: ornate.

OTHER MATERIAL EXAMINED. — Philippines. Bohol Sea, Camiguin Island, W side of White island, offshore sand cay, 9°15.38’N, 124°39.12’E, 18 m, 19.IV.1997 (Sample: CRRF). — SW Bohol, Panglao Island, 9°32.27’N, 123°43.54’E, 20 m, 21.IV.1997 (Sample: CRRF).

DESCRIPTION

The type specimen, 7 × 4 cm in size, was attached by its left side to the ceiling of a cave. The tunic is mammillated, transparent and without epibionts ( Fig. 125E ). It contains a network of dichotomously branching blood vessels making small ampullae just under the tunic surface, but these are not reflected on the surface by papillae. The siphons are far apart and slightly protruding. There are about 20 lobes on the oral siphon. They are round, not dentate, but a white pigment line gives them a sharp appearance. In both siphons the velum has a network of white pigment. The whole body wall is reddish; the siphons and the tentacles are the most coloured.

The other specimens are somewhat different. One of them is transparent without lines on the siphon lobes and has a yellow velum. Another has white lines on the siphons, and its vascular ampullae are white, giving it a spotted look, but its velum is not visible. This appearance accounts for the species name. All pigments disappear in fixatives.

The body wall is thin and the musculature is weak. On the right side the muscles cover the whole body in a loose network. On the left side there are only some longitudinal fibres, while the transverse musculature is only present in the dorsal part, anterior to the gut.

There are about 30 long, cylindrical oral tentacles irregularly arranged. In life they are red. They are planted on a crest where some very small ones are intercalated. The prepharyngeal area is narrow, covered by small papillae. The prepharyngeal band has two unequal blades, the anterior one is high and wavy. The dorsal curve is filled by a flat dorsal tubercle ( Fig. 81C ). It has two openings in the type specimen ( Fig. 81C ) but only one in other specimens. The neural ganglion is far from the dorsal tubercle, at 3/5 of the inter-siphonal distance. There are no accessory openings of the neural gland or its channel. The dorsal lamina is high and double down to the neural ganglion, then becomes a thin blade without teeth, and then farther posteriorly it has thin teeth that correspond to its ribs. It is prolonged without change below the oesophagus entrance. On the right side of the dorsal lamina, the branchial papillae are elongated.

The oesophagus entrance is 3/5 the way down the branchial sac which is prolonged beneath the gut. The branchial tissue is thin, slightly pleated. The meshes contain six to 10 stigmata each. The papillae are large and flat. There are no intermediate papillae. The gut is massive ( Fig. 81A, B ) with an uncommon shape. The anus is anterior to the top of the gut loop, which is at the level of the oesophagus entrance. The stomach is almost longitudinal; its thin wall reveals its internal glandular ridges. The ascending limb of the intestine is narrow and the descending limb dilated. The rectum is large. The gaping anus has a rolled, plain rim. The shape of the gut does not correspond to that of any other Ascidia species of the western Pacific.

Ascidia sydneiensis Stimpson, 1855 ( Figs 82 ; 125F )

Ascidia sydneiensis Stimpson, 1855: 387 . Type locality: Australia, Port Jackson.

MATERIAL EXAMINED. — Palau. Southwest Islands, Sonsoral, 5°20.88’N, 132°13.80’E, 9 m, 24.VII.1995. — Koror, West Uchelbeluu Reef, 7°16.41’N, 134°31.43’E, 31 m, 9. V.1997. — Koror, West Uchelbeluu Reef, 7°15.96’N, 134°31.28’E, 112 m, 15.IX.1998 (Samples: CRRF).

Papua New Guinea. Milne Bay Province, N side of East Cape, Hiliwau, 10°15.65’S, 150°42.75’E, 3 m, 27. V.1998 (Sample: CRRF).

Tonga. Vava’u dock, 18°40.62’S, 174°01.70’W, 1 m ( MNHN P5 ASC.A 311).

REMARKS

This very common species ( Figs 82 ; 125F ) is widely distributed. Its shape and consistency are highly variable and depend on the habitat. Generally, more stout forms are found in pollut- ed areas, such as harbours, that are rich in organic matter.

A. sydneiensis from the Pacific Ocean is very closely allied to Ascidia canaliculata Heller, 1878 from the Atlantic Ocean and South Africa, in which dorsal tubercle openings are in a double spiral. Both species are vicariant.

Figures

FIG. 81. — Ascidia ornata n. sp.; A, left side of the body; B, internal side of the gut loop; C, dorsal tubercle. Scale bars: A, B, 1 cm; C, 1 mm.

FIG. 125. — A, Perophora modificata Kott, 1985; B, Perophora namei Hartmeyer & Michaelsen, 1928; C, Ecteinascidia bandaensis Millar, 1975; D, Ascidia gemmata Sluiter, 1895 s.l.; E, Ascidia ornata n. sp.; F, Ascidia sydneiensis Stimpson, 1855.

FIG. 82. — Ascidia sydneiensis Stimpson, 1855; A, B, left and right sides of the body; C, neural area; D, internal side of the gut loop. Scale bars: A-C, 1 cm; D, 2.5 mm.