Pyura scortea, KOTT, 1985

Monniot, Claude, 2002, Stolidobranch ascidians from the tropical western Indian Ocean, Zoological Journal of the Linnean Society 135 (1), pp. 65-120 : 102-105

PYURA SCORTEA KOTT, 1985 ( Figs 27B , 29 )

Pyura scortea Kott, 1985: 324 , fig. 159 – Western Australia; not Monniot C., 1989: 487 – New Caledonia.

Material

Seychelles: Mahé, anse à la Mouche.

Mozambique: Ibo Island, coll. C. Monniot, 1995.

Djibouti, coll. C. Monniot, 1996.

Description

The body lies in a thick, hard tunic that is corrugated at the surface. The body shape varies according to the substrate; the animal is fixed by its ventral side. The specimen collected in the Seychelles is 4 cm in diameter, the others are smaller. All have long, red siphons set apart by half the body length. The tunic lining of the siphons remains red in formalin. The siphonal spinules form conical scales with a straight edge ( Fig. 27B ).

The body wall is thin but contains a strong musculature. Longitudinal fibres coming from the siphons cross each other, and the most dorsal ones fuse. The oral tentacles are slightly branched. The prepharyngeal band forms a deep dorsal V prolonged by a groove. The slit of the round dorsal tubercle is C-shaped, opening anteriorly. The six high folds on each side contain about 20 vessels each. Each longitudinal vessel ends in a papilla at the oesophagus entrance.

The gut forms a long, rather open loop, without a secondary curve ( Fig. 29A,C ). The anus rim is wavy. The hepatic gland is divided along the stomach into several lobes, resembling a cauliflower ( Fig. 29A,C ).

The gonads, one on each side, comprise lobes linked by thin ducts to a straight axial gonoduct ( Fig. 29A–C ). Only the terminal part of the sperm duct and oviduct are curved toward the cloacal aperture; they are narrow and do not contain gametes. The gonads are only loosely connected to the body wall.

There are no endocarps.

The cloacal velum is wide, arising from a scalloped basal membrane.

Remarks

The specimens collected in the western Indian Ocean correspond well to Kott’s (1985) description. Monniot (1989) identified large specimens from New Caledonia as P. scortea . These specimens differ by having endocarps of variable number and size, and a hepatic gland that forms a single mass. P. scortea ’s constancy of anatomical characters in the Indian Ocean confirms the holotype description and indicates that the New Caledonian specimens belong to a different species.

PYURA TONGAEA MONNIOT C. & MONNIOT F., 1976 ( Figs 27C , 30 )

Pyura tongae Monniot C. & Monniot F., 1976: 381 , fig. 6A – Mozambique; Millar, 1988: 840 – Mozambique.

Pyura sansibarica , not Michaelsen, 1908, Millar, 1956: 929 – Mozambique.

Material

Madagascar: Nosy-Be, coll. R. Plante, 1966

Djibouti, coll. C. Monniot, 1996.

Description

The body, 1–2.5 cm in diameter, is covered with sediment. The short siphons have needle-shaped spinules ( Fig. 27C ). The tunic is about 1 mm thick, embedded with sand except for a thin, soft, internal layer. The body wall is transparent and shows a musculature comprising large fibres, regularly spaced and crossed, that issue from the siphons. The gonads and gut can be seen in transparency.

Both siphons have a large velum.

About 20 oral tentacles are arranged in three orders of size and are twice ramified. The prepharyngeal band has two unequal rims, the anterior one thick and the posterior one a blade. The dorsal tubercle forms a button with a C-shaped opening, that lies in a dorsal indentation. The long dorsal lamina is cut into sharp languets.

The branchial sac has six high folds on each side. 18–20 longitudinal vessels were counted on the folds and 3–4 vessels between the folds. These vessels end around the oesophagus entrance in long, sharp papillae. There are parastigmatic vessels.

The oesophagus is very short ( Fig. 30C ). The hepatic gland presents several very branched lobes along an unconspicuous stomach. The hepatic lobe located on the pyloric side of the stomach is the most voluminous lobe; it is pedunculated and of a pale colour. The long primary loop of the intestine reaches almost to the anterior limit of the branchial sac ( Fig. 30C ). The rectum curves in a short secondary loop. The anus is wide open and simple.

The gonads are in the shape of an arc on each side of the body ( Fig. 30A–C ). The left gonad occupies the intestinal loop ( Fig. 30C ). The gonads are made of lobes protruding from the body wall and alternating regularly on each side of a wide oviduct ( Fig. 30C ). Each lobe comprises an ovarian part and an apical testis ( Fig. 30D ). A common sperm duct lies on the ovarian axis. The genital papillae are close together, opening near the anus ( Fig. 30E ).

Variably numerous endocarps lie along the outer curve of the intestinal loop ( Fig. 30C ). They are only at the level of the stomach and rectum in small specimens, but all around the gut in larger animals. Small endocarps are also found on the gonad lobes, but none along the heart.

The cloacal velum is particularly well developed. There are no cloacal tentacles.

Remarks

The general organization of this species is very similar to that of Pyura gangelion ( Savigny, 1816) . It differs by having a smaller size, the constant presence of embedded sand in the tunic, and the absence of endocarps on the body wall itself.

Pyura tongaea is currently known only from the western tropical Indian Ocean.

Figures

Figure 27. Siphonal spinules: A, Pyura gangelion; B, Pyura scortea; C, Pyura tongae; D, Microcosmus madagascariensis; E, Microcosmus pupa. Scale bars: A,C,D,E = 100 mm, B = 20 mm.

Figure 29. Pyura scortea: A, specimen from the Seychelles ventrally opened. B, right side of the body. C, specimen from Djibouti. Scale bars = 1cm.

Figure 30. Pyura tongae: A,B, both sides of the body. C, body ventrally opened. D, part of the gonad. E, genital papillae. Scale bars: A,B,D = 1mm, C,E = O.5mm.