Polycarpa rima Monniot F. & Monniot C., 1996

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 330-333

Polycarpa rima Monniot F. & Monniot C., 1996

( Fig. 96 )

Polycarpa rima Monniot F. & Monniot C., 1996: 254 , fig. 54C, D, pl. 9F. Type locality: Papua New Guinea. MATERIAL EXAMINED. — Palau. Airai Ongelungel, 7°20.69’N, 134°32.08’E, 7 m, 15.V.1996 (MNHN S1 POL.B 380).

Federated States of Micronesia. Yap, Goofnuw Channel, 9°34.27’N, 138°12.26’E, 18 m, 5.VIII.1995 ( MNHN S1 POL.B 382).

Fiji. Viti Levu, Suva Harbour Channel, 18°08.63’S, 178°24.07’E, 3 m, 23.X.1996 ( MNHN S1 POL.B 381).

Tonga. Tongatapu, Hakau Mama’o Reef, 20°59.80’S, 175°12.85’W, 7 m, 19.XI.1997 ( MNHN S1 POL.B 415).

Papua New Guinea. Coral Sea, Eastern fields, 10°00.66’S, 145°39.90’E, 65 m, 14. VI.1998 ( MNHN S1 POL.B 416). — Louisiade Archipelago, Deboyne Lagoon, Nivani Island, 10°47.46’S, 152°23.08’E, 12 m, 30. V.1998 ( MNHN S1 POL.B 404). — Milne Bay Province, Samarai, 10°36.98’S, 150°39.77’E, 27 m, 10. VI.1998 ( MNHN S1 POL.B 423).

DESCRIPTION

The specimens are 6 to 8 cm long, 3 cm wide and 2 cm thick. The protruding siphons, 1 to 2 cm long, are 1 cm in diameter. They clearly have four lobes with the aperture forming a cross when contracted. The body is fixed by the left posterior side. In life the tunic is a pale ochre or grey and the cloacal siphon has four pinkish patches on the lobes. When fixed in formalin the tunic becomes a dark brown.The tunic is partly covered with epibionts, algae and didemnids. It is thin and soft but tough. It interior surface is slightly nacreous.

The 1 mm thick body wall is opaque. It is made of three layers: one external, thin, with granules, one internal, containing a dark musculature, and a lighter internal layer containing the gonads and full of granules, which are pale with a black spot or entirely dark. The granules around the gonoducts are always dark. The internal side of the siphons has a continuous layer of longitudinal fibres.

There are about 50 oral tentacles in three or four orders of size, those of smallest order with a variable development. The prepharyngeal band is close to the tentacular ring. It is made of two fleshy pads on the sides of a deep groove ( Fig. 96C ); it makes a dorsal V and is prolonged by a more or less developed groove towards the dorsal lamina. The dorsal tubercle is flat and full of granules. Its opening is complex ( Fig. 96C, D ). The dorsal lamina is fleshy and low. Its height increases near the oesophagus. The endostyle is not attached to the body wall and is particularly high (1 mm).

The branchial sac is light brown with black granules on its external side. One formula is:

R. E. 7 18 4 16 5 17 5 15 3

D.L. 2 13 7 16 4 16 4 14 6 E. L.

The formula is slightly different in specimens from Yap;

R. E. 3 10 4 13 3 15 3 (8 2 5) 0

D. L. 3 13 4 16 3 14 3 14 3 E. L.

The first fold on the right doubles posteriorly when four of the six sinuses of the anterior part of the branchial sac form a pseudo-fold. The formula becomes ([7 to 8] [5])2 D. L. etc. The first vessel on the right parts from the dorsal lamina posteriorly. By the oesophagus entrance it is separated from the dorsal lamina by more than 20 stigmata. The folds are high and slightly overlap each other. There are more than 10 elongated stigmata in a mesh between the folds and five to eight on the folds. There are no parastigmatic vessels.

The gut occupies the posterior third of the left side ( Fig. 96A ). The stomach is externally smooth. In section the glandular grooves are irregular and not well-marked. The rectum has some black granules. It is attached to the body wall. The anus has a smooth or undulated rim and opens at some distance from the cloacal siphon.

The gonads ( Fig. 96B ) are included in the thickness of the body wall. In section they are spherical with a central ovary circled by elongated male lobes. The ducts open in the middle of a mass of black granules. The male papilla diverges the female papilla. In one specimen the gonads are numerous (about 90 on the right and 70 on the left side) but almost inactive. They are less numerous (about 37 on the right and 28 on the left) in specimens from Yap ( Fig. 96A ), but they are functional, more protruding, and form somewhat polygonal masses.

There are three endocarps in the intestinal loop, one of them a thin blade following the rectum. There are no endocarps elsewhere.

REMARKS

This species seems common and widely distributed in the western tropical Pacific Ocean. It belongs to the group that Kott (1985) names the “pedunculata group” which comprises species having one to three endocarps in the gut loop, and gonads included in the body wall and encircled by granules. These species, some of which have bright colours in life, generally become dark brown or black in fixatives. The species differ in the shape of the dorsal tubercle, the gonad structure and particularly the shape of the testis lobes, and the shape of the gut loop and anus.

Polycarpa pedunculata Heller, 1878 has few gonads, elongated and clearly protruding into the cloacal cavity, with testis lobes deeply divided.

Polycarpa ovata Pizon, 1908 is a more or less pedunculate species with a simple dorsal tubercle and lobed testis lobes.

Polycarpa molguloides Herdman, 1882 , adapted to live on soft bottoms, shows differentiation of the tunic and has a coating of sand. The dorsal tubercle is simple, the testis lobes are ramified, and the anus is lobed.

Polycarpa viridis Herdman, 1880 is slightly pedunculate with a complex dorsal tubercle, lobed testis lobes and a divided anus. There is a single endocarp, in the gut loop.

Polycarpa obscura Heller, 1878 has a black tunic in life, with an orange ring around each siphon. The dorsal tubercle is complex and the testis lobes are very elongated. As described by Kott (1985) P. obscura is a pedunculate species, erect, with a long oral siphon oriented toward the current.

Polycarpa flava Kott, 1985 is a bright yellow in life, and has a simple dorsal tubercle, a lobed anus, and only one endocarp.

P. descipiens Herdman, 1906 is a small species (2 cm) with a simple dorsal lamina, divided testis lobes, and a rolled and lobed anus.

P. rima Monniot F. & Monniot C., 1996 is distinguished by a gut with a long rectum; the gonads have long ducts protruding into the cloacal cavity. The siphons of P. rima have a light internal surface.

P. rima approaches the species group Polycarpa mytiligera ( Savigny, 1816) - P. pigmentata Herdman, 1906 . But both those species are larger (more than 10 cm), erect, and totally black in life. They have only one or two endocarps in the intestinal loop.

Figures

FIG. 96. — Polycarpa rima Monniot F. & Monniot C., 1996; A, gonads distribution; B, polycarp; C, D, dorsal tubercles. Scale bars: A, 1 cm; B, 2 mm; C, D, 1 mm.