Cystodytes hapu Monniot C. & Monniot F., 1987

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 235-237

Cystodytes hapu Monniot C. & Monniot F., 1987

( Figs 26 ; 27 ; 116C )

Cystodytes hapu Monniot C. & Monniot F., 1987: 64 , fig. 23A-D, pl. IVE-F. Type locality: New Caledonia. MATERIAL EXAMINED. — Palau. Koror, Ngerikuul Pass, 7°19.22’N, 134°29.24’E, 7 m, 23.V.1994 (MNHN A3 CYS 96).

Maldives. S Male Atoll, oceanside North reef, 4°07.54’N, 73°30.55’E, 7 m, 1.X.1997 ( MNHN A3 CYS 105).

DISTRIBUTION. — Polynesia, Palau, and Maldives Islands.

DESCRIPTION

The colonies are encrusting, 5 mm thick, grey, with a round edge. The smooth surface is pierced by slits that are the openings of amphipodsheltering cavities. The systems are not very regular. The superficial tunic is translucent and without spicules but contains brown, round pigment cells ( Fig. 116C ), which are also found around the zooids in formalin preserved specimens. Deeper inside the colony the spherical brown cells are irregularly scattered.

Numerous small spherical spicules made of concentric needles are distributed through the subsurface thickness of the tunic, but are more numerous below that and between the zooids. They have an average diameter of 50 µm ( Fig. 27 ). Disc-shaped spicules 600 to 800 µm in diameter ( Fig. 27 ) make capsules around the zooids and around the larvae. There are very few spicules of intermediate size.

The zooids lie perpendicular to the colony surface. The oral siphon has six to eight lobes, the cloacal siphon six to seven lobes ( Fig. 26A ). The thoraces are too contracted to count the stigmata or to distinguish a body-wall fold on the waist.

The digestive loop has the common shape of the genus, with a large central space containing the rosette of testis lobes. Ten to 12 oval testis lobes converge on the sperm duct, which runs straight from its origin ( Fig. 26B ). The oocytes are locat- ed near the oesophagus. Developed larvae are incubated in a pouch protruding on a short and narrow peduncle from the waist of the zooid ( Fig. 26C ) (giving the species its Polynesian name). The larval size varies, with a maximum trunk length of 1.4 mm. The three anterior papillae, in a line, are encircled by a ring made of four fused pairs of ampullae ( Fig. 26D, E ), a common structure in the genus Cystodytes . On the left side only, an ampullar structure with a deeply toothed margin lies over the anterior part of the larval body ( Fig. 26E ). The larvae are not gemmiparous, but two stigmata rows are soon pierced. Each larva has its own capsule of flat spicules.

REMARKS

This sample from Palau differs from the type of C. hapu Monniot C. & Monniot F., 1987 from Polynesia in the abundance of small spicules, and the tooth-edged structure on the larva. Nevertheless, thin vascular processes are also present on the left larval body side in Polynesian colonies. Specimens collected in the Indian Ocean have both small spicules and larger ones in capsules and larvae in a pedunculate brood pouch with ampullae on the left side. They are assigned to the same species.

Two New Caledonian species have spicules in pin-cushions. Cystodytes luteus Monniot F., 1988 has a different anatomy of its zooids and larvae, and Cystodytes mucosus Monniot F., 1988 has numerous siphonal lobes, abundant mucus, and no dark pigment, and its larvae are incubated at the stomach level.

Figures

FIG. 26. — Cystodytes hapu Monniot C. & Monniot F., 1987; A, B, zooid in two parts; C, incubating zooid; D, right side of the larva; E, anterior part of the left side of the larva. Scale bars: A, B, D, E, 0.5 mm; C, 1 mm.

FIG. 27. — Cystodytes hapu Monniot C. & Monniot F., 1987, spicules. Scale bar: 100 µm.

FIG. 116. — A, Clavelina robusta Kott, 1990; B, Citorclinum laboutei Monniot F. & Millar, 1988; C, Cystodytes hapu Monniot C. & Monniot F., 1987; D, Eudistoma album Monniot F., 1988; E, Eudistoma fluorescens n. sp.; F, Eudistoma fucatum n. sp.