Aplidium cyclophorum, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 207-208

Aplidium cyclophorum n. sp.

( Fig. 3 )

TYPE MATERIAL. — Papua New Guinea. Southern Louisiade Archipelago, Long Reef, 11°11.10’S, 151°51.57’E, 12 m, 5. VI.1998 ( MNHN A1 APL.B 418).

ETYMOLOGY. — From the Greek kuklos: circle and phor-: wearing.

DESCRIPTION

The single colony is a large pad 8 × 4.5 cm and 1.5 cm thick. The colour in life is unknown, but it is dark brown in formalin. The surface is smooth without sand or any epibiont. There are well-separated depressed systems made of a circular groove into which the oral siphons open. In the centre of each system is a cloacal aperture at the top of a short chimney. The zooids are perpendicular to the colony surface and much retracted.

The oral siphon has six petal-like lobes. In some cases the three ventral lobes are much longer than the three dorsal ones ( Fig. 3A ).

The cloacal aperture is narrow with a stout single languet on its anterior rim ( Fig. 3A, B ). When the aperture is expanded five teeth appear on its posterior margin.

The thoracic musculature is strong with numerous regularly criss-crossed transverse and longitudinal fibres. We counted 20 longitudinal fibres on each side in one zooid.

The branchial sac contains 18 to 20 rows of numerous stigmata. There are no parastigmatic vessels. The dorsal languets are short.

The gut forms a rather short loop. The stomach has a neat typhlosole with a fold on each side, but other plications are not pronounced ( Fig. 3A ). In some specimens the stomach wall has five obscure longitudinal folds ( Fig. 3C ). The gut was too contracted to see intestinal compartments. There is no narrowing between the abdomen and post-abdomen. The ovary lies at some distance from the gut, followed by numerous testis follicles in two rows filling the whole post-abdomen ( Fig. 3A ).

Only poorly advanced larvae are incubated in the cloacal cavity of some zooids ( Fig. 3B ). The oldest found has sensory organs and a trunk 0.3 mm long encircled by the tail.

REMARKS

This species is much like A. longithorax Monniot F., 1987 . The shape of the colony is about the same, but in that species the colour is always yellow in formalin (Monniot F. 1987: 525; Monniot F. & Monniot C. 1996: 139, pl. 1c). A. longithorax differs in having eight lobes at the oral siphon, an elongated stomach with five deep folds, a different musculature, and an unperforated space between the stigmata and the endostyle.

Aplidium crateriferum ( Sluiter, 1909) and A. clivosum Kott, 1992 have systems of different shape, some sand embedded in the tunic, and a cloacal lip inserted clearly anterior to the cloacal aperture.

Figures

FIG. 3. — Aplidium cyclophorum n. sp.; A, zooid; B, thorax of another zooid; C, abdomen. Scale bar: A, B, 1 mm; C, 0.5 mm.