Diplosoma pavonia Monniot C. & Monniot F., 1987

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 278-279

publication ID	https://doi.org/ 10.5281/zenodo.5391440
persistent identifier	https://treatment.plazi.org/id/F57D87A3-FF92-3175-E82C-FDB6FCA41320
treatment provided by	Marcus
scientific name	Diplosoma pavonia Monniot C. & Monniot F., 1987
status

Treatment

( Figs 62 View FIG ; 121F View FIG )

Diplosoma pavonia Monniot C. & Monniot F., 1987: 60 , fig. 21. Type locality: Solomon Islands.

MATERIAL EXAMINED. — Indonesia. N Sulawesi, West of Manado, 1°23.52’N, 124°32.64’E, 5 m, 14.IV.1993 ( MNHN A 2 DIP. A 144).

DESCRIPTION

The colonies are dark green, growing on dead corals ( Fig. 121F View FIG ). The common cloacal cavity is filled with symbiotic algae. The plate-like colony is attached to the coral by a short, narrow peduncle. The colony surface is flat with a central common cloacal aperture. The tunic is hard and resistant. The zooids have a long oral siphon, often curved, as in the type specimen, with six small lobes. The cloacal siphon is large but the body wall covers the first and fourth rows of stigmata. The retractor muscle is insert- ed very posteriorly on the oesophageal peduncle. The abdomen has the common shape of the genus. There are two voluminous testis follicles. The sperm duct is straight. The ovary, with a very large oocyte, lies on the side of the testis.

The larvae are large, 1.1 mm in diameter for the trunk ( Fig. 62 View FIG ). They have many adhesive papillae in a line, some of them on bifurcated stems ( Fig. 62 View FIG ), and two pairs of digitiform ampullae. The larvae are gemmiparous. A very large “rastrum” in the shape of two wings occurs at the base of the tail. Many larvae in the colony had degenerated, with only the adhesive papillae and sensory organs remaining in their bodies.

REMARKS

This species is recorded again here for the first time.

Diplosoma redika Monniot F., 1994 ( Figs 63 View FIG ; 122A View FIG )

Diplosoma redika Monniot F., 1994: 7 , fig. 3. Type locality: New Caledonia.

MATERIAL EXAMINED. — Philippines. Mindanao, Davao, Pakiputan Strait, 7°07.36’N, 125°40.11’E, 33 m, 3.IV.1996 ( MNHN A 2 DIP. A 134). — Bohol Sea, Camiguin Island, 9°12.89’N, 124°38.03’E, 7 m, 18.IV.1997 ( MNHN A 2 DIP. A 143).

DESCRIPTION

The colonies are very thin and soft, transparent ( Fig. 122A View FIG ), in large gelatinous sheets encrusting calcareous pebbles. In life, the common cloacal apertures are atop erect small chimneys on colonies that are 5 to 10 mm thick underwater, but reduced to 1 mm thick when fixed. The zooids are colourless, hardly visible as pale flecks in the vitreous tunic, which often falls apart into mucous strings.

The oral siphon is narrow with short lobes. The cloacal aperture is wide. The number of stigmata could not be counted in the very retracted zooids. There is no retractor muscle ( Fig. 63A View FIG ).

The abdomen is folded under the thorax. The gut loop is narrow, and a single testis follicle protrudes from its exterior side ( Fig. 63A, B View FIG ). The sperm duct is enlarged along the testis, where it makes a groove. The ovary is located against the testis, but the maturing oocytes enter a pedunculate pouch of the body wall that rapidly isolates them from the mother zooid ( Fig. 63B View FIG ).

Numerous small larvae ( Fig. 63C View FIG ) lie in the basal layer of the colony. They measure 0.5 mm in diameter. They have three urn-shaped adhesive papillae on thin stems and four pairs of well-separated clavate ampullae. There is one bud on each side of the larval body.

REMARKS

This species, previously described from New Caledonia, is characterised by its colourless, translucent, gelatinous colonies, a single testis follicle, and a larva with four well-separated ampullae on each side of the adhesive papillae. The distribution of this species may be wide but its fluid consistency excludes any collection except by SCUBA and so may have excluded as well wider records from the tropical western Pacific.