Polycitorella stellifera, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 253-254

Polycitorella stellifera n. sp.

( Figs 41B ; 42 ; 118F )

TYPE MATERIAL. — Papua New Guinea. Milne Bay Province, East Cape, Boia Boia Waga Island, overhang wall, 10°12.26’S, 150°44.75’E, 18 m, 27. V.1998 ( MNHN A3 POL.B 7).

ETYMOLOGY. — From the Latin stellifer: stellate.

A

DESCRIPTION

The incrusting colonies are 1 cm thick, with stellate white systems encircled by greenishbrown areas ( Fig. 118F ). The colony is soft, rather gelatinous at the surface. There are nine to 10 zooids in a system’s circle, and the cloacal openings are grouped in the centre of each system.

The expanded zooids ( Fig. 42A ) measure 8 to 9 mm in length, with the thorax much longer than the abdomen. Both siphons are very short with six lobes. There are 24 oral tentacles in two orders, sometimes with small ones between them. The thorax is wide and inflated, with very thin longitudinal and transverse muscular fibres that are regularly spaced and crossed. The branchial sac contains four stigmata rows grouped in pairs ( Fig. 42A ), with 35 to 40 stigmata in the first two half rows. The dorsal part of the first row curves anteriorly.

The gut loop is straight with a smoothwalled stomach ( Fig. 42A, B ) in the middle of the abdomen or slightly anteriorly of that. The different parts of the intestine are not well-separated. The anus opens at the base of the last row of stigmata. The gonads lie in the gut loop. There are about 10 elongated testis follicles, and the ovary lies close to the sperm duct ( Fig. 42B ): when mature, an oocyte protrudes beneath the abdomen ( Fig. 42C ).

The spicules are large (0.4 mm in diameter), with a few long, tapering branches ( Fig. 41B ). They look like some spicules of Lissoclinum species. Pigment cells, brown and round lie scattered in the tunic between the spicules.

REMARKS

This species differs from all other Polycitorella species in its branchial sac with only four rows of stigmata. P. hospitiolum ( Savigny, 1816) has six rows of stigmata; all others species have many more rows.

Figures

FIG. 41. — Spicules; A, Polycitorella mariae Michaelsen, 1924; B, Polycitorella stellifera n. sp. Scale bars: 10 µm.

FIG. 42. — Polycitorella stellifera n. sp.; A, zooid in a male phase; B, detail of the gut; C, zooids in a female phase. Scale bar: A, B, 1 mm; C, 2 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.