Eudistoma gracilum Kott, 1990

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 240-241

publication ID	https://doi.org/ 10.5281/zenodo.5391440
persistent identifier	https://treatment.plazi.org/id/F57D87A3-FFF8-3113-E864-FCAEFEA01280
treatment provided by	Marcus
scientific name	Eudistoma gracilum Kott, 1990
status

Treatment

? Eudistoma gracilum Kott, 1990 View in CoL

( Fig. 30 View FIG )

Eudistoma gracilum Kott, 1990: 211 View in CoL , fig. 79e, f. Type locality: Queensland.

MATERIAL EXAMINED. — Palau. Ngemelis, Bailechesengel Island, Big Drop Off, 7°06.22’N, 134°15.06’E, 1.5 m, 21.XI.1996 ( MNHN A3 EUD 221).

DESCRIPTION

Colonies consist of flat cushions 0.5 cm thick and 1 to 3 cm in diameter made of one lobe or several lobes pressed together, arising from a harder common base. The tunic is translucent and soft, but difficult to tear. It is colourless in formalin.

The zooids are very short ( Fig. 30A View FIG ): wellrelaxed ones are only 3 mm long, with a 1 mm thorax and 2 mm abdomen. They extend from the surface of the colony to its common base. Both siphons have six lobes. The cloacal siphon is inserted a little lower than the neural ganglion and is longer than the oral siphon. There are six short oral tentacles. The three rows of stigmata have about 12 perforations in each half row.

The thoracic musculature is made of strong longitudinal fibres extending down to the abdominal extremity and fine transverse fibres particularly visible around the incubatory cavity.

The abdomen is twice the length of the thorax when relaxed, and then the gut loop is straight. The round, smooth walled stomach is posterior, followed by an inflated mid-intestine ( Fig. 30A, B View FIG ). There are a few testis follicles in a bunch in the bottom of the gut loop and one central oocyte. The mature gonads protrude on the left side of the gut loop. There are one or two vascular extensions at the posterior end of the abdomen.

Two or three embryos are incubated in the cloacal cavity. They are very small, with trunks only 300 µm long ( Fig. 30C View FIG ). They have three adhesive papillae on short, stout peduncles separated by two odd ampullae.

REMARKS

This example of this species differs from the original species description in a tunic with a firmer consistency, the absence of dark pigment cells in preservative, and a smaller larva. Also the colonies may be constituted of several flat cushions on a common base. Nevertheless, the general organisation of the zooids and larvae and their very small size place our colonies in the species Eudistoma gracilum Kott, 1990 .