Herdmania pallida ( Heller, 1878 )

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 341-343

? Herdmania pallida ( Heller, 1878)

( Figs 104; 129F)

Cynthia pallida Heller, 1878: 96 , pl. III, figs 17; 18. Type locality: unknown.

Herdmania momus – Monniot C. 1992: 16, fig. 6A.

MATERIAL EXAMINED. — Palau. Koror, Ngederrak Reef along Ngel Channel, seagrass bed, 7°17.90’N, 134°28.34’E, 19. VI.1996 ( MNHN S2 HER 23). — Koror, Mutmelachel, Ucheliungs Island, algae flat, 7°18.56’N, 134°30.10’E, 17.II.1995 ( MNHN S2 HER 24).

DESCRIPTION

The body is round and the tunic has no epibionts. Some sediment particles adhere to the tunic (Fig. 129F). The siphons were red in life. In preservative the tunic becomes transparent, colourless, and soft. All tissues contain acicular spicules with rings of spines.

There is a large oral velum. The tentacles are bushy and pinnate. The dorsal tubercle is very protruding, with a horseshoe-shaped opening, and included in a deep V of the prepharyngeal band ( Fig. 104C, D). The dorsal lamina is long with numerous sharp languets. The musculature is restricted to the siphonal areas ( Fig. 104A, B). In the largest specimen, 4 cm in diameter, the branchial sac has nine folds on the right side and eight on the left side with the formula:

R.E. 0 3 0 8 1 12 1 14 1 17 1 16 1 17 1 14 2 9 2 D.L. D.L. 2 11 2 14 1 17 1 17 1 17 1 14 1 10 1 6 2 E.L. The youngest specimens have fewer branchial folds and fewer vessels on them.

The gut forms an open loop that contains the left gonad ( Fig. 104C, D). The rectum is slightly curved. The hepatic gland has two lobes ( Fig. 104C, D) made of very numerous digitiform papillae with round tips. The anus is plain.

A

B

The gonads, one on each side, are elongated and straight ( Fig. 104C, D). The ovary is central in an elongated mass; the testis lobes encircle it. Well-separated in young specimens, the testis lobes join when the animal grows. Their ducts are directed toward the axis of the ovary, where they fuse to make a straight common sperm duct running on the ovary’s internal side. The simple male papilla lies close to the wide short female papilla ( Fig. 104E). There is no membrane developed around the female opening

There is a large cloacal velum but no cloacal tentacles. The spicules are of the usual shape in the genus Herdmania : long spindle-like spicules with two pointed ends in the tissues, and short sticks with a round end raised in numerous small points in the tunic, as described by Lambert G. & Lambert C. (1987).

REMARKS

By its straight ovary this species recalls the cosmopolitan form described as C. pallida Heller, 1878 . It clearly differs from the typical H. momus ( Savigny, 1816) from Suez, which has a contorted ovary and multiple openings of small sperm ducts, a lobed anus – all characters confirmed by a re-examination of old material from Suez. Numerous forms have been described and that identified as H. momus differ mainly in the shape of the gonads and their ducts. The number of branchial folds and longitudinal vessels are not reliable for identification, as they vary according to the size and maturity of the specimens. The variability also reflects the substrate and habitats where the animals are collected, a higher variability being found in harbours.