Aplidium rosaceum, Monniot & Monniot, 2001

Monniot, Françoise & Monniot, Claude, 2001, Ascidians from the tropical western Pacific, Zoosystema 23 (2), pp. 201-383 : 215-216

publication ID	https://doi.org/ 10.5281/zenodo.5391440
DOI	https://doi.org/10.5281/zenodo.5467952
persistent identifier	https://treatment.plazi.org/id/F57D87A3-FFD1-3134-EA50-FF3BFC2716E0
treatment provided by	Marcus
scientific name	Aplidium rosaceum
status	sp. nov.

Treatment

Aplidium rosaceum View in CoL n. sp.

( Figs 10 View FIG ; 113B)

TYPE MATERIAL. — Papua New Guinea. Louisiade Archipelago, Deboyne Lagoon, 10°47.46’S, 152°23. 08’E, 12 m, 30. V.1998 ( MNHN A1 APL.B 415).

ETYMOLOGY. — From the Latin rosaceus: rosaceous.

DESCRIPTION

One or several lobes arise from a common base. They are 3 to 3.5 cm high, cylindrical, and about 2.5 cm in diameter with a flat top. The tunic is an opaque pink (Fig. 113B). No sand adheres to the surface. Each head has a single system or a group of just a few systems. The tunic is raised around each system, which has a central common cloacal opening encircled by a groove where the oral siphons open.

The zooids are very large, averaging 25 mm long ( Fig. 10A, B View FIG ). The oral siphon ( Fig. 10C View FIG ) has six petal-like lobes and a red spot between each lobe. The cloacal aperture is a narrow hole, its anterior rim prolonged by a wide languet deeply cut into three pointed lobes ( Fig. 10C View FIG ). There is a median dorsal protrusion posterior to the base of the cloacal siphon ( Fig. 10A View FIG ).

The large branchial sac has 22 rows of about 40 stigmata on each side.

The thoracic musculature that issues from each siphon is dense, with numerous longitudinal fibres especially on the dorsal side. This gives the thorax a distorted aspect with its dorsal side shorter than its endostylar region ( Fig. 10A View FIG ). In contracted animals, there is a constriction between the thorax and abdomen.

The abdomen is about half the size of the thorax ( Fig. 10A View FIG ). The stomach is mid-way down the descending gut loop. Its wall has oblique, irregular, and branched folds, emphasized by a brown pigment. In transverse section we counted 10 to 12 ridges. There is an annular post-stomach and an oval mid-intestine. The rectum opens three rows above the base of the branchial sac with an anus that has two large lobes.

The post-abdomen is as long as the thorax plus abdomen. The ovary lies at mid-length, followed by a loose cluster of testis follicles ( Fig. 10B View FIG ). The gonads are included in an abundant reserve tissue. In addition, above the gonads and up to the base of the gut loop, the post-abdomen is filled by a mass of white tissue of unknown origin.

No larvae were present in the colonies observed.

REMARKS

This species has several original characters: large zooids with a particularly large branchial sac, a stomach reticulated with low irregular plications, and a long post-abdomen but with clustered testis follicles. The colony shape reminds one of Aplidium clivosum Kott, 1992 but the zooids are distinctly different.