Clavelina maculata, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 233-234

Clavelina maculata n. sp.

( Figs 25 ; 115E)

TYPE MATERIAL. — Philippines. Bohol Sea, Balicasag Island SW of Bohol, 9°31.23’N, 123°40.98’E, 22.IV.1997 ( MNHN A3 CLA 114).

ETYMOLOGY. — From the Latin maculatus: spotted.

DESCRIPTION

The sample is a group in which large zooids are isolated down to their base (Fig. 115E). Each zooid produces long, ramified stolons interlaced with those of nearby individuals. This bush of zooids does not contain developing buds, so it is difficult to decide if it is a colony or a group of solitary individuals. The tunic is soft on the thorax and more resistant on the abdomen, which is frequently covered by epibionts. In a relaxed animal, the thorax and abdomen are of equal length ( Fig. 25A, B ). In living specimens the tunic is opaque white with dark blue spots distributed without particular order (Fig. 115E). The terminal oral siphon has two latero-dorsal white triangles. The cloacal siphon is slightly posterior.

The internal surface of the siphons and the transverse vessels are black. When preserved in formalin, the tunic becomes transparent and the body takes on a reddish colour, making the examination of the muscles difficult.

The thoracic musculature ( Fig. 25C ) comprises bundles issuing from both siphons and about 10 bundles coming from the ventral zone. On the lateral and dorsal sides of the body, these fibres are thin and rarely anastomosed. Left and right musculatures join in the postero-dorsal part of the thorax. Ventrally the bundles are much stronger, ramifying and anastomosing before fusing with the muscles alongside the endostyle. As the musculature is stronger ventrally, the contraction of the body displaces the cloacal siphon to an apical position and the oral siphon laterally ( Fig. 25C ). On the abdomen, the musculature becomes more delicate and almost invisible below the stomach.

There are a dozen oral tentacles, all large, planted on the posterior side of a high crest and linked to it by ribs. The prepharyngeal band has two high parallel crests; it is not indented dorsally. The dorsal tubercle opens as a simple hole. The dorsal lamina has long languets on the transverse vessels. The branchial sac has 19 rows of stigmata.

The oesophagus is short in these contracted specimens but probably longer in life. We have not seen a dilation of the oesophagus anterior to the stomach, but its absence may be due to the contracted state of the body. The stomach has the shape of a saddle, its concave side applied to the dilated intestine. A conspicuous typhlosole separates two glandular areas with lateral crests ( Fig. 25A ). The intestine is not differentiated into regions. The anus opens at the base of the cloacal cavity ( Fig. 25B ).

The diffuse ovary is on the left side of the gut loop. The testis lobes, which lie on the intestine posteriorly to the stomach, are not well-developed in these specimens ( Fig. 25B ). An enormous heart with an obvious internal membrane dilates all the right side of the abdomen below the stomach.

The larvae are incubated inside a dilated oviduct in the posterior part of the left cloacal cavity, and they develop further in the cloacal cavity. The fully developed larvae become blackish and reach 1.1 mm in length. They have three adhesive papillae in a triangle ( Fig. 25D ).

REMARKS

By its morphology C. maculata n. sp. is close to C. meridionalis ( Herdman, 1891) , a solitary species. Both species have these traits in common: a pigmentation concentrated in the tunic and making it opaque, a darkly coloured body wall and branchial vessels that become reddish in formalin, and the disposition of the thoracic musculature and its progressive disappearance posterior to the stomach. But in the solitary species of Clavelina , the bottom of the gut loop reaches to the stolons at the base of the tunic, while in C. maculata n. sp. there is still an erect part of the tunic under the abdomen containing a long vascular process. C. maculata n. sp. does not have the basal thickening of hard tunic which, in C. meridionalis (Monniot F. & Monniot C. 1996) , represents the trace of the successive regenerations of the solitary zooid. The dense stolonial network, probably related to the large size of the heart, is far different from the short root-like vascular processes of solitary species.

Clavelina moluccensis ( Sluiter, 1904) ( Figs 24D ; 115F)

Podoclavella moluccensis Sluiter, 1904: 5 . Type locality: Indonesia.

Synonymy and distribution: see Clavelina moluccensis

– Monniot C. 1997a: 208, fig. 7e.

MATERIAL EXAMINED. — Papua New Guinea. Milne Bay Province, China Straits, 10°34.50’S, 150°40.73’E,

9 m, 9. VI.1998 (Sample: CRRF).

Philippines. Bohol Sea, Balicasag Island SW of Bohol, 9°31.02’N, 123°40.83’E, 3 m, 15.IV.1997 ( MNHN A3 CLA 107).

Mariana Islands. Guam, Apra Harbour, Jade Shoals, 6-18 m, 5. VI.1997, coll. Paulay( MNHN A3 CLA 121).

REMARKS

Some specimens in this collection have the usual appearance of the species, with transparent zooids with three dark spots in a line perpendicular to the siphon axis (Fig. 115F). In another colony the colour is more opaque and intensifies in older zooids, in which, as well, the three characteristic spots, present in young specimens disappear. In colonies with zooids of both colours, many zooids show dilations of some branchial vessels to produce clear ampullae.

This species is well-characterised by its musculature ( Fig. 24D ) and the position of the anus well anterior to the oesophagus entrance.

Figures

FIG. 25. — Clavelina maculata n. sp.; A, B, both sides of a zooid; C, thorax; D, larva. Scale bars: A-C, 2 mm; D, 0.5 mm.

FIG. 24. — Clavelina fecunda (Sluiter, 1904); A, zooid; B, abdomen; C, larva; D, Clavelina moluccensis (Sluiter, 1904), zooid. Scale bars: A, C, 0.5 mm; B, D, 2 mm.