Phallusia sp.

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 311-312

publication ID	https://doi.org/ 10.5281/zenodo.5391440
persistent identifier	https://treatment.plazi.org/id/F57D87A3-FFB1-3154-EA1C-FA96FB3D1398
treatment provided by	Marcus
scientific name	Phallusia sp.
status

Treatment

Phallusia sp.

( Figs 85 View FIG ; 126C View FIG )

MATERIAL EXAMINED. — Tonga. Vava’u, sunken wreck Glen McWilliam near Neiafu, 18°40.25’S, 173°59.45’W, 18 m, 11.XI.1997 ( MNHN P5 PHA 95).

DESCRIPTION

This large size specimen (10 cm) was found inside clumps of calcareous algae on a sunken wreck. The individual is attached by two third of its left side. Though hidden in the algae, this animal has a tunic devoid of epibionts. It is white and hard ( Fig. 126C View FIG ). The siphons are far apart. The long oral siphon has a dozen flat lobes with patches of white pigment. The siphons are grooved and interiorly they have lines of white pigment prolonged as far as the circle of oral tentacles. All pigmentation disappears after formalin preservation. The thick, stiff tunic contains a network of blood vessels ending in small papillae at the surface, but there are no vascular ampullae as there are in other Phallusia species. The body is elongated and its siphons are far apart ( Fig. 85A, B View FIG ). The body wall is thin. The weak musculature is made of a regular network of thin bundles covering the whole right side of the body and the anterior part of the left side. The oral tentacle ring is far down at the base of the siphon. There are about 45 tentacles of very different sizes, not distributed in regular orders. The prepharyngeal band has two equal slightly folded blades. The neural ganglion is very posterior. The neural gland channel has some accessory apertures ( Fig. 85E View FIG ); it opens through a small dorsal tubercle slit in the shape of a C that is open anteriorly ( Fig. 85D View FIG ).

The whole prepharyngeal area and the dorsal tubercle are covered with small papillae. These are also present less numerously on the internal surface of the oral siphon.

The dorsal lamina is double as far as the neural ganglion. In this anterior region, the right side is even but the left blade is dentate. In its middle part the dorsal lamina has irregular teeth and is moderately high, and after the oesophagus entrance it becomes progressively lower. On the right side is a row of papillae joined posteriorly in a right dorsal lamina identical to that of the left side.

The branchial tissue is well-plicated and passes beyond the gut. There are about 60 regularly spaced longitudinal vessels on each side. The branchial meshes are square. The papillae are high with lateral extensions. There are no intermediate papillae.

The gut is located in the posterior part of the body ( Fig. 85A View FIG ). The stomach has irregular ridges. The rectum is dilated even when the gut is empty ( Fig. 85C View FIG ). The anus has two lobes.

The ovary is more developed on the internal side of the gut ( Fig. 85C View FIG ), with a mass of small lobes, few of which are visible externally ( Fig. 85A View FIG ). The testis lobes cover a large part of the gut. The gonoducts end in a common papilla beside the anus. This papilla remains orange even after preservation in formalin.

About 20 fish larvae occupied the posterior part of the cloacal cavity on the left side.

REMARKS

This species is placed in the genus Phallusia Svigny, 1816 according to the presence of some accessory openings on the neural gland channel.

Family PLURELLIDAE Kott, 1973