Aplidium intextum, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 209-210

Aplidium intextum n. sp.

( Figs 5 ; 112C )

TYPE MATERIAL. — Philippines. Mindanao, Davao, Pakiputan Strait, rubble, 7°06.81’N, 125°39.99’E, 33 m, 30.IV.1996 ( MNHN A1 APL.B 383).

ETYMOLOGY. — From the Latin intextus: embroided.

DESCRIPTION

The colonies are white and firm, encrusting, up to 3 cm thick, in flat cushions superficially ornamented with swellings separated by transparent and colourless furrows on which the oral apertures open. This suggests a work of embroidery ( Fig. 112C ) (thus the species name). The common cloacal apertures are not located at the groove crossings. The tunic is rubbery hard and translucent interiorly.

The oral siphon has six short lobes above a strong sphincter. The cloacal aperture, which also has circular muscle fibres, faces the second row of stigmata. Even in one colony, its rim may be prolonged by a simple lip-like languet ( Fig. 5B ) in some zooids, while in others the languet lies immediately anterior to the cloacal aperture ( Fig. 5A ). The long thorax has 11 to 12 rows of about 20 stigmata apiece. There are about 15 longitudinal thoracic muscles on each side.

The abdomen is as long as the thorax ( Fig. 5A ). The oesophagus is long. The cylindrical stomach has 15 to 16 deep longitudinal folds that are never interrupted. The ovary lies at some distance from the gut loop and is followed at some distance by two densely packed lines of testis follicles occupying the posterior half of the abdomen, down to the heart ( Fig. 5A ).

The larvae ( Fig. 5C ) are incubated in a distended cloacal cavity ( Fig. 5B ), protruding into the posterior part. We usually found four of them at different stages. The trunk measures 0.5 mm. The three adhesive papillae are not equidistant. They are not separated by ampullar protrusions but are rather lined on each side by an irregular row of clear round vesicles ( Fig. 5C ).

REMARKS

This species closely resembles Aplidium lineatum Monniot F. & Monniot C., 1996 in its colony structure, the branchial sac, and the arrangement of the testis into densely packed rows in the posterior post-abdomen. It differs in its narrow cloacal siphon with an undivided languet, and in having fewer and more regular stomach folds.

This species also differs from A. controversum Monniot F. & Monniot C., 1996 in having fewer stomach folds, in the testis follicles densely gathered in two compact lines very far down the postabdomen, and in the different design of its colony surface.

Figures

FIG. 5. — Aplidium intextum n. sp.; A, zooid; B, thorax of another zooid; C, larva. Scale bars: A, B, 1 mm; C, 0.5 mm.

FIG. 112. — A, Aplidium breviventer n. sp.; B, Aplidium cerebrum n. sp.; C, Aplidium intextum n. sp.; D, Aplidium longithorax Monniot F., 1987; E, Aplidium macrolobatum Kott, 1992; F, Aplidium nadaense (Nishikawa, 1980).