Distaplia Della Valle, 1881

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 256-257

Genus Distaplia Della Valle, 1881

Distaplia mikropnoa ( Sluiter, 1909) ( Figs 44 ; 119B)

Polyclinum mikropnous Sluiter, 1909: 94 , pl. 5, fig. 1. Type locality: Indonesia.

Distaplia mikropnoa – Tokioka 1967: 129, fig. 46, Palau.

MATERIAL EXAMINED. — Palau. Koror, West Malakal Harbour mouth, 7°20.37’N, 134°25.7’E, 40 m, 20. V.1994 ( MNHN A3 DIS 69).

DESCRIPTION

The colonies have several lobes on thick peduncles arising from a common base. In formalin, the largest lobe has a head as long as the peduncle 2 cm and a head diameter of 1.8 cm. The colonies in life were pink; the colour has faded in formalin fixative but a red spot remains at the neural ganglion. There are several common cloacal openings on each head; these apertures have a lobed edge and are situated apically at the ends of double rows of zooids (Fig. 117B). The zooids lie perpendicular to the colony surface.

The zooids have wide cloacal openings with two lips ( Fig. 44A ). The anterior one has a pointed or lobed tip and some transverse musculature. There are 12 oral tentacles of two orders. The branchial sac has more than 25 stigmata on each side in the first row. There are no parastigmatic vessels.

The gut forms a wide open loop ( Fig. 44A ). The stomach has numerous neat folds. There is a pyloric ampulla in the loop.

The gonads are appended in a posterior pouch of the abdomen ( Fig. 44A ). About 15 male follicles are in a tight cluster. The sperm duct is directed posteriorly and then forms a loop against the ovary before running anteriorly to follow the rectum ( Fig. 44A ).

The larvae ( Fig. 44B ) are incubated in pouches hanging on the right side of the zooid’s thorax ( Fig. 44A ). They have a trunk 1.1 mm long and three adhesive papillae in a triangle. The larval gut, folded under the thorax, already has a plicate stomach.

REMARKS

The zooids of this species are very similar to those of Distaplia stylifera ( Kowalevsky, 1874) . They differ essentially in the absence of parastigmatic vessels.

Tokioka’s (1967) description from Palau specimens exactly corresponds to our material, with similar irregular double rows of zooids, pedunculate colonies, and an absence of parastigmatic vessels.

Figures

FIG. 44. — Distaplia mikropnoa (Sluiter, 1909); A, zooid; B, larva. Scale bars: A, 1 mm; B, 0.5 mm.