Herdmania pallida, (HELLER, 1878)

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 113-115

HERDMANIA PALLIDA ( HELLER, 1878) ( Figs 35D , 37 )

Cynthia pallida Heller, 1878: 96 , pl. III, figs 17,18 – Mauritius, Jamaica, western Pacific; Herdman, 1882: 143 – Fiji.

Cynthia pallida billitonensis Sluiter, 1885: 183 – Indonesia.

Cynthia rosea Sluiter, 1887: 264 – Indonesia.

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

Herdmania pallida: Monniot F. & Monniot C., 2001: 341 – western Pacific.

Material

Types of Cynthia rosea, ZMA TU 400 and Cynthia pallida billitonensis, ZMA TU 895.

Pacific Ocean: Guam, Honolulu, New Caledonia, Hawaii, Vietnam.

Atlantic Ocean: Guadeloupe, Martinique, Brazil, Panama.

Indian Ocean: Djibouti, Zanzibar, Mozambique.

Australia: Sharks Bay.

Description

Heller’s original description does not define a type specimen, but instead blends observations of individuals collected in the three oceans. My identification of specimens as Herdmania pallida is based on later descriptions and especially that of Michaelsen (1919).

Specimens from different sources measure 1–6 cm across, with a tunic that is always soft, wrinkled, and more-or-less covered with epibionts or sometimes sediment. The red colour of the tunic is variable in inten- sity and extension. It disappears when the animals are fixed in formalin or alcohol. The internal lining of the tunic is gelatinous.

Extracted from the tunic, the body is laterally flattened. The body wall, as all other tissues, contains abundant spindle-like spicules ( Fig. 35D ). They are very similar in size and shape to those in H. momus . The musculature is strong in the dorsal half of the body, with a thick sphincter around the siphons and radiating, well-separated bundles, extending down to the level of the middle of the gut loop on the left side, and reaching the gonad on the right ( Fig. 37A ). The ventral side of the body is devoid of muscular ribbons.

The oral tentacles are generally large and secondarily ramified, but some individuals from the same stations have thin, poorly branched tentacles.

The prepharyngeal band is indented into a deep V. The slit of the dorsal tubercle is U-shaped, anteriorly opened with its ends rolled inward in several turns that protrude.

The dorsal lamina has numerous sharp languets. The branchial sac has 8–9 folds on each side, often eight folds on the left side and nine on the right side according to the body size. The folds are high, overlapping each other, with 8–14 longitudinal vessels each. The stigmata are cut with parastigmatic vessels. The endostyle is very long, attached to the stomach wall in its terminal part.

The gut makes a long, simple, and open loop ( Fig. 37A ); the top does not reach the anterior limit of the branchial sac. The short oesophagus leads to a poorly defined stomach. The intestine has a constant diameter and ends in a plain-edged anus; it is not linked to the dorsal lamina. The hepatic gland comprises one lobe on the right side of the ventral line and a larger lobe on the stomach, of irregular outline, covering less than half of the ascending limb of the gut ( Fig. 37A ). The hepatic papillae are dense, thin, with round tips.

There is one long gonad on each side ( Fig. 37A ). The left gonad lies along the whole descending limb of the gut, inside the digestive loop. The right gonad occupies the middle of that side. In each gonad the ovary is sinuous, central, surrounded by a widely developed testis ( Fig. 37B ) that often almost entirely covers the ovary when fully mature. The oviduct is short, attached to the body wall. When they are visible, the male ducts can be seen to converge to join an axial sperm duct that follows the ovary ( Fig. 37B ) and opens

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Figure 36. Herdmania momus : A,B,C,D, specimen from Cyprus. A, body ventrally opened. B, proximal part of a gonad. C, female papilla. D, anus. E,F, young specimen from Mozambique. E, body ventrally opened. F, part of the gonad showing multiple male papillae. Scale bars: A = 1 cm, B,C,D,E = 5 mm, F = 0.2 mm.

by a simple hole against the female papilla. In very large individuals the course of the gonoducts cannot be seen.

The heart extends in a long tube parallel to the endostyle and contains a round concretion.

A scalloped membrane fringes the base of the cloacal siphon.

Remarks

The deep V of the prepharyngeal band around the dorsal tubercle is remarkable, and so is the shape of the dorsal tubercle’s opening: the ends of both horns closely rolled and protruding. The straight, long gonads with short, simple genital papillae are also characteristic of this species.

Herdmania pallida has a worldwide distribution in warm, shallow waters. It settles easily on artificial substrates, even in polluted areas. The species sometimes lives in very dense populations.

Figures

Figure 35. Spicules of internal tissues.A,B, Herdmania coutieri sp. nov., C, Herdmania momus, D, Herdmania pallida. Scale bars: A = 100mm, B, C, D = 10 mm.

Figure 37. Herdmania pallida: A, specimen from Israel ventrally opened. B, apical part of a gonad. Scale bars: A = 5 mm, B = 1mm.