Cynthia momus Savigny, 1816: 90

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 111

Cynthia momus Savigny, 1816: 90 , pl. 1, fig. 2, pl. VI,

fig. 1 – Red Sea.

Rhabdocynthia pallida: Sluiter, 1905:14 – Djibouti, Obok and Musha.

Halocynthia momus: Sluiter, 1905: 15 – Djibouti.

Pyura momus typica: Michaelsen, 1919:54 – Red Sea.

Pyura momus : aut. mult.

Material

Type?: S2 HER 41 Red Sea, J.C. Savigny, 1801 .

Other material examined: Red Sea: Mascate, coll. M. Maindron, 1877; Suez, coll. Letourneux, 1880; Perim Island, coll. F. Jousseaume, 1891; Aden, coll. R. PH. Dollfus, 1929; coll. ISRSE, 1962.

Djibouti: Musha Island, coll. C. Gravier, 1904; Djibouti, coll. C. Monniot, 1996.

Lebanon: Kafar Abida , 9 m, coll. G. Bitar , 1995; Beyrouth, coll. H. Zibrowius ; Ibail , 15 m, coll. H. Zibrowius.

Cyprus: Famagouste Harbour , 7 m, coll. H. Zibrowius , 1998.

Yemen: Socotra Island, coll. C. Monniot, 1997.

Mozambique, coll. Heurtel, 1886; Ibo Island, coll. C. Monniot, 1995

Description

The external aspect is highly variable according to the place where the specimens have been collected. The tunic is always soft and somewhat sclerified at the surface, which is much corrugated. Epibionts are present on old specimens and those collected in harbours. The siphons are protruding, their spacing is variable. The tunic contains short spicules.

The body wall is thin. The musculature is mostly dorsal, with strong sphincters around the siphons and regularly spaced radiating fibres, that extend on the right side as far as the gonad and on the left side as far as the gut loop (Fig. 36A,E) The oral tentacles are tertially ramified; large and small tentacles alternate along the base of a velum. The prepharyngeal band forms a shallow dorsal V. The dorsal tubercle has a U-shaped opening with horns rolled in.

The dorsal lamina has sharp languets. The branchial sac has seven to nine high folds on each side, according to the body size.

The gut lies in the posterior part of the body on the left side, where it makes an open loop (Fig. 36A,E). The very short oesophagus leads to an inconspicuous stomach. The intestine does not curve in a secondary loop (Fig. 36A,E). The anus is far from the oesophagus and edged with round lobes, irregular in shape and in number (usually 10; Fig. 36D). The hepatic gland is made of one lobe on the right side of the oesophagus and two linked lobes lying along half the length of the ascending limb of the gut (Fig. 36A).

The gonads are elongated, one on each side. The left gonad is totally included inside the gut loop, against the rectum (Fig. 36A,E). The right gonad lies in the middle of the right side of the body (Fig. 36A,E). Each gonad has a long, sinuous ovary ending in a short wide oviduct whose opening is surrounded by a large collarlike membrane (Fig. 36C), well figured by Savigny. The testis almost entirely covers the ovary; it has many lobes placed edge-to-edge and opens by short, simple papillae on the ovary’s internal surface (Fig. 36B). In young specimens it appears that a single sinuous sperm duct receives minor ducts from several testis lobes (Fig. 36F), and this common sperm duct then opens on the ovary surface by numerous papillae distributed along its length. In old specimens, with bulky gonads, the sperm ducts do not remain visible and even the papillae are scarcely apparent (Fig. 36B), for they are only small sessile holes along the ovary surface.

The cloacal velum is scalloped.

Spicules are abundant in all organs. Some of them reach 1 cm in length. They are made of annular rings of about 40 spines for the largest ( Fig. 35C ).

Remarks

The above account applies as much to specimens in very old collections stored in the MNHN as it does to others collected more recently. It corresponds exactly to the detailed description provided by Savigny, and to a specimen collected in 1801 that I believe is the type .

The distribution of this species covers the eastern Mediterranean Sea, the Red Sea, and the western Indian Ocean down to Mozambique. Many other specimens of Herdmania collected worldwide have been attributed to the species Herdmania momus , based on the presence of acicular barbed spicules in their tissues and the general disposition of their gut and gonads. But in the process, several species have been confused as one. They differ in the distribution of the musculature, the shape of the gut and the hepatic gland, and the shape of the gonads and their ducts. The shape of the dorsal tubercle and the number of branchial folds also have to be considered, even when these traits are more variable, more dependent on body size and consequently more difficult to assess.

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.