Polycitor circes Michaelsen, 1930

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 249-250

Polycitor circes Michaelsen, 1930

Polycitor circes Michaelsen, 1930: 495 . Type locality: Australia. — Monniot F. & Monniot C. 1996: 184, Indonesia, and synonymy.

A

B

MATERIAL EXAMINED. — Papua New Guinea. Louisiade Archipelago, Conflict Group, 10°43.52’S, 151°44.54’E, 20 m, 29. V.1998 ( MNHN A3 POL.A 32).

Polycitor giganteus ( Herdman, 1899) ( Figs 38A ; 118B )

Polyclinum giganteum Herdman, 1899: 79 . Type locality: South Australia.

Synonymy: see Polycitor giganteus – Kott 1990: 171, fig. 64, pl. 13d-h.

MATERIAL EXAMINED. — Papua New Guinea. Louisiade, Nivani, 10°47.46’S, 152°23.08’E, 7 m, 30. V.1998 ( MNHN A3 POL.A 33).

DESCRIPTION

The translucent colony ( Fig. 118B ), 6 cm in diameter, was collected in a crevice. From the surface, the zooids can be seen in the tunic, but there are no white rings around the siphons, only white spots on the oral lobes. The tunic’s consistency is firm with a very resistant surface layer and a more gelatinous internal tunic.

The zooids are not crowded and not distributed in organised systems. Both siphons are tubular with six lobes. The longitudinal thoracic muscles converge toward the base of the endostyle. There are 14 rows of numerous stigmata. The zooids are strongly contracted, and so the structure of the abdomen was not clearly evident. The stomach has two longitudinal bands.

The larvae are numerous in the cloacal cavity, up to six in a zooid. The larval trunk measures 1.25 mm. The three adhesive papillae, in a line, have long thin stems; between them are four round ampullae which are not well-formed ( Fig. 38A ).

REMARKS

This spectacular species was, until now, known only from Australia, so it is surprising to find it in Papua New Guinea. It differs from P. circes Michaelsen, 1930 in its larval structure.

Polycitor translucidus Kott, 1957 ( Figs 38B ; 118C )

Polycitor translucidus Kott, 1957a: 81 . Type locality: western Australia. Synonymy: see Kott 1990: 177, fig. 66 d-g.

MATERIAL EXAMINED. — Palau. Babeldaob, West channel, 7°32.42’N, 134°28.37’E, 10 m, 25.X.1997 ( MNHN A3 POL.A 29).

DESCRIPTION

The colonies are dome-shaped, firm, gelatinous, glassy, with a short and thick peduncle. The tunic is perfectly transparent and colourless, and reveals the widely spaced, radially arranged zooids ( Fig. 118C ). The largest colonies have a hemispherical head 5 to 6 cm in diameter and 2 to 3 cm thick. There is no sediment on or in the colonies.

The fixed zooids are deeply retracted into the colony head. Both siphons have six rounded lobes. The thoracic musculature is mostly longitudinal with eight to 10 strong bundles, prolonged in ribbons along the abdomen. There are 12 to 14 rows of elongated stigmata, separated by high transverse membranes. About 35 stigmata were counted in the second half-row.

The abdomen is long, but so contracted that the different parts of the gut cannot be detailed. The stomach is very posterior, cylindrical, with a smooth wall raised in two longitudinal crests on each side of the typhlosole. The gonads, of ordinary appearance, are located in the gut loop. One or several irregular but thick vascular processes prolong the abdomen.

The embryos are incubated (up to 10) in large number in the thoracic cloacal cavity. The most advanced larvae are rather small (0.75 mm for the trunk), with three adhesive papillae in a line at the top of long and very thin stems. Between them are three pairs of odd ampullae that have a round tip on one side and pointed tip on the other side ( Fig. 38B ).

REMARKS

This species is very close to the European P. crystallinus (Renier, 1804) , which has even smaller but very similar larvae. P. translucidus is widely distributed from western Australia into the western and central tropical Pacific Ocean.

Figures

FIG. 38. — Larva; A, Polycitor giganteus (Herdman, 1899); B, Polycitor translucidus Kott, 1957. Scale bars: 0.5 mm.

FIG. 118. — A, Eudistoma sp.; B, Polycitor giganteus (Herdman, 1899); C, Polycitor translucidus Kott, 1957; D, Polycitorella coronaria Monniot F., 1988; E, Polycitorella mariae Michaelsen, 1924; F, Polycitorella stellifera n. sp.