Aplidium grisiatum Kott, 1998

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 208-209

Aplidium grisiatum Kott, 1998

( Fig. 4 )

Aplidium griseum Kott, 1992a: 551 , fig. 80, preoccupied by Aplidium griseum Lahille, 1890 , Mediterranean Sea. Replacement name. Type locality: Great Barrier Reef.

Aplidium grisiatum Kott, 1998: 119 . Replacement name.

MATERIAL EXAMINED. — Palau. Koror, “White Face” sand slope S of Lighthouse Reef, 7°15.84’N, 134°27.68’E, 62 m, 22.VIII.1997 (Sample: CRRF). — Lighthouse Reef Basin, 7°16.72’N, 134°28.35’E, 47 m ( MNHN A1 APL.B 416).

DESCRIPTION

The largest colony measures 7 × 3 × 5 cm, but it surrounds a sponge and its thickness actually does not exceed 1 cm. Its surface has a clear design of meandriform systems, well-isolated from each other. There is not any zooid external to the systems. Each system has one central common cloacal opening. Each system is externally and superficially fringed by an accumulation of fine sand grains in a convoluted line. The centre of each system is perfectly transparent, devoid of sand, and reveals the upper part of the zooids. The remainder of the tunic contains sparse sediment, except that on the sides of the colonies it is abundant. The colour in life is unknown; in formalin it is brown with light brown zooids, which may have been red. The thin zooids reach 1 cm in length ( Fig. 4A, B ). The thorax as longer as the abdomen. Zooids have six oral lobes. The narrow cloacal siphon lies at the level of the second stigmata row ( Fig. 4A, C ). The cloacal languet is pointed, inserted well ahead of the cloacal aperture ( Fig. 4A, C ).

There are 13 to 14 rows of stigmata, but their number in any row could not be counted.

The abdomen has the usual gut compartments. The stomach has eight deep longitudinal folds ( Fig. 4A ).

The post-abdomen is long ( Fig. 4A, B ). We have found only an ovary in the posterior part, far from the gut, but no testis follicles. The postabdomen shortens when the ovary is mature.

One or two embryos are incubated in the cloacal cavity ( Fig. 4A ). The elongated trunks of mature larvae are 0.8 mm long with three well-spaced adhesive papillae and two short, pointed median ampullae. On each side of the trunk is an anterior crown of dense small vesicles ( Fig. 4D ).

REMARKS

This species exactly corresponds to the description of Aplidium griseum by Kott (1992a) but the name she chose was preoccupied by Aplidium griseum Lahille, 1890 for a Mediterranean species and so Kott (1998) created the replacement name A. grisiatum .

The superficial design of the colony is characteristic.

Figures

FIG. 4. — Aplidium grisiatum Kott, 1998; A, B, two parts of a zooid; C, another zooid; D, larva. Scale bars: A-C, 1 mm; D, 0.25 mm.