Aplidium pictum, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 214

Aplidium pictum n. sp.

( Figs 9 ; 113A) TYPE MATERIAL. — Papua New Guinea. South coast, Coutance Island on barrier reef, 10°13.80’S ,

148°06.87’E, 9 m, 12.VI.1998 (MNHN A1 APL.B 414).

ETYMOLOGY. — From the Latin pictus: painted.

DESCRIPTION

The round cushions of this species, inflated in life (Fig. 113A), become very flat when fixed. In each system there is a central common cloacal aperture toward which channels in which the zooids open in double rows converge. The test is colourless. The zooids have a black ring around the oral siphons and black pigment on the cloacal languets (hence the species name). The strongly contracted zooids are very short, only 4-5 mm long ( Fig. 9 ). The oral siphon has six lobes. The cloacal aperture is rather large. Its anterior border has a languet dominated by three long prolongations with dark pigment ( Fig. 9 ). The remainder of the body is colourless except for a darker tinge in the stomach folds.

There are 10 rows of stigmata in the branchial sac. The abdomen is short. The gut compartments are not well-separated. The stomach, wider than it is long has 20 to 30 longitudinal folds ( Fig. 9A ). There is no annular post-stomach in the contracted animals.

The post-abdomen is short. The ovary lies immediately behind the gut, followed by a series of testis follicles in a line. The zooids were not fully mature. There is a brood pouch on the right side of the rectum, at the junction of the thorax and the abdomen. This pouch is empty but present in all zooids, even those with no trace of gonads ( Fig. 9 ).

No larvae were found.

REMARKS

This species is closely similar to Aplidium sacciferum n. sp. and Aplidium altarium ( Sluiter, 1909) as described by Kott (1992a). The cushion-like colonies, the small size of the zooids, the 10 rows of stigmata, and the numerous stomach folds are the same in these species; but the other two lack the black ring around the oral aperture and the large cloacal languet so deeply cleft into three long lobes. The presence of an incubatory pouch in the new species is also distinctive.

Figures

FIG. 9. — Aplidium pictum n. sp., two zooids. Scale bar: 1 mm.