Eudistoma punctatum, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 243-244

Eudistoma punctatum n. sp.

( Figs 33 ; 117C)

TYPE MATERIAL. — Papua New Guinea. East Cape, Taodovu Reef, 10°21.21’S, 150°56.27’E, 6 m, 6. VI.1998 ( MNHN A3 EUD 222).

ETYMOLOGY. — From the Latin punctus: point.

DESCRIPTION

The colony is made of several lobes arising from a common base. Each lobe has a cylindrical peduncle covered with epibionts and an enlarged transparent head, in which one can see the zooids arranged in a circle. The cloacal openings are grouped in the centre of each system. The zooids have two large yellow spots between the siphons (Fig. 117C): this emphasizes the arrangement of zooids in one circular system in each lobe. The largest lobes of the colony reach only 8 mm in height. The zooids ( Fig. 33A, B ) are long, with their thoraces in the heads of the colony and their abdomens in the peduncles. All were contracted. The siphons are tubular with six elongated lobes. They each have a pale yellow ring that becomes brown in formalin. Two large spots lie on each side of the neural ganglion, yellow in life and dark brown in formalin preservative. The remainder of the zooid is colourless.

The strong musculature is made of longitudinal and transverse fibres covering the whole thoracic surface. The longitudinal bundles are prolonged on the abdomen.

There are three rows of elongated stigmata. The first row is curved anteriorly on the dorsal side. There are about 30 stigmata in the second row on each side. The abdomen is longer than the thorax and has a posterior stomach. The gonads are located in the bottom of the gut loop, with numerous testis lobes and a central ovary ( Fig. 33A ).

In a few zooids, one immature larva with ocellus and otolith was incubated in the cloacal cavity ( Fig. 33C ). The three anterior adhesive papillae were not well-developed. The trunk is 0.75 mm in length.

REMARKS

The shape of the colonies, the translucent tunic, and the expanded head on a stiff peduncle reminds one of Eudistoma rubra Tokioka, 1954 , but that species is much larger and lacks the two well-marked pigment spots between the siphons. The first row of stigmata runs anteriorly beside the dorso-median line in both species, but this is a rather common arrangement in the genus Eudistoma . The pigmentation and the translucent heads of these colonies are uncommon in the genus Eudistoma Caullery, 1909 .

Figures

FIG. 33. — Eudistoma punctatum n. sp.; A, B, zooids; C, larva. Scale bars: A, B, 1 mm; C, 0.5 mm.