Herdmania armata, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 337-339

Herdmania armata n. sp.

( Figs 100 ; 101; 129E)

TYPE MATERIAL. — Papua New Guinea. Nivani, coarse sand and rubble, 10°47.46’S, 152°23.08’E, 10- 18 m, 29. V.1998 ( MNHN S2 HER 20).

ETYMOLOGY. — From the Latin armatus: armed.

DESCRIPTION

Two individuals were found on a sandy bottom, the largest 20 cm in height and 15 cm in diameter. The tunic in life was dark brown, covered with epibionts, the internal surface of the siphons yellow (Fig. 129E) with a pink rim. Both siphons have a square section; they are far apart and diverging. The tunic is thick, leathery, very hard. All tissues of the body are filled with spindle-like spicules ( Fig. 101), all parallel, giving a nacreous quality to the external side of the body wall. The muscles are strong but difficult to see through the opaque pale tissue. The internal and external sides of the siphons are tinted in red.

The tentacles are thick and flattened with thick ramifications of the first order and small ones of the second order. There are eight large, wellspaced tentacles ( Fig. 100B ) with eight smaller ones between them and small intermediate ones.

The prepharyngeal groove is thin and draws a deep dorsal V. The large dorsal tubercle occupies the whole space inside the V. It is pierced by numerous small holes, making a network of convoluted lines ( Fig. 100C ).

The branchial sac contains abundant spicules in the main transverse vessels. There are 14 overlapping folds on each side. In the middle of the branchial sac there is an average of 28 fully developed longitudinal vessels on the folds and eight between the folds. There are also smaller intermediate, flat longitudinal vessels. The transverse vessels are of several orders and as a result the stigmata are very small compared with the size of the branchial sac, with three to four in a mesh.

The digestive tract occupies the whole left side of the body ( Fig. 100A ). The gut loop is closed. The oesophagus is not distinct. The stomach is not wider than the intestine. No compartments can be identified along the intestine.

The hepatic gland is made of several massive lobes, one on the internal side of the oesophagus, the others in a line along the internal side of the loop ( Fig. 100A ). On the stomach these round lobes are dark brown. The anus opens against the oesophagus with a scalloped margin.

The gonads ( Fig. 100A ) are spherical masses included in an opaque tissue. On the left side they lie in a line along the rectum inside the gut loop. On the right side they are large, in a longitudinal line of four masses; the most anterior mass seems empty. These masses are linked by the gonoducts. Each gonad has a single male papilla joined to the female papilla at the distal end of the last gonad lobe, near the cloacal siphon. There are no endocarps on the body wall.

REMARKS

This species is unique for its very large size, the abundance of its spicules, and the peculiar shape of the hepatic gland and of the gonads. It has been placed in the genus Herdmania on the basis of the presence of abundant spicules, but its other anatomical characters do not correspond well to the general structure of species in the genus, and so its assignment to the genus Herdmania remains doubtful.

Figures

FIG. 100. — Herdmania armata n. sp.; A, specimen ventrally opened; B, oral tentacle; C, dorsal tubercle. Scale bars: A, 10 cm; B, C, 0.5 cm.