Cystodytes philippinensis (Herdman, 1886)

KOTT, PATRICIA, 2003, New syntheses and new species in the Australian Ascidiacea, Journal of Natural History 37 (13), pp. 1611-1653 : 1619-1621

Cystodytes philippinensis (Herdman, 1886)

(figure 2A–E)

Cystodytes philippinensis Herdman, 1886: 140 ; Tokioka, 1950: 123.

Cystodytes hapu Monniot and Monniot, 1987: 64 ; 2001: 235.

Distribution. New records: Queensland (Heron I., QM G308020; Swain Reefs QM G305801). The species previously was known from the western Pacific ( Philippines, Herdman, 1886; Palau Is, Tokioka, 1950; Monniot and Monniot, 2001; French Polynesia, Monniot and Monniot, 1987; the Maldives, Monniot and Monniot, 2001).

Description. Both living and in preservative one of the colonies (QM G305801) is a hard pearl-grey tongue-shaped slab about 6 mm thick and about 8 cm long. The colour results from the spherical black pigment cells amongst the large globular spicules. The colony from Heron I. (QM G308020) is an even, tough mat about 5 mm thick with its surface divided into white patches (owing to the absence of pigment) separated by a network formed by dark reddish brown pigment mixed with white spicules. The branchial apertures are in the darker areas and the test around the thoraces (the upper part of the colony) also contains dark pigment amongst the spicules. In both colonies globular spicules to 0.09 mm diameter are crowded in the test making it hard and rigid. Parallel, vertical hour glass-shaped compartments for the zooids interrupt the test, the thoraces in the upper half of the colony, and the abdomina in the lower half. The basal half of each compartment is surrounded by a capsule of three or four overlapping layers of saucer-shaped spicules (to 0.5 mm diameter). This capsule is itself surrounded by the crowded globular spicules that occupy the remainder of the test. The saucer-shaped spicules are present only around the abdominal parts of each zooid compartment. In both the newly recorded colonies the upper half of each compartment is empty, the zooids being contracted and withdrawn into the basal (abdominal) half and the abdomen pulled up to the right of the thorax. On the surface of the colony are numerous large common cloacal apertures, each surrounded by three to five branchial apertures (six-lobed). The common cloacal cavities are fairly shallow depressions in the surface, receiving the openings of the atrial siphons which, when distended, presumably fill the spaces in the stiff, rigid test between the thoracic compartments and cloacal cavities. The test over the cloacal cavities is thin and in the preserved specimens lies in the folds around the central aperture. In the living specimen this thin test may be forced up into a short chimney by the excurrent flow of water, probably exposing the whole of the cloacal cavity to the exterior.

Zooids are black in life but beige coloured in preservative. Four rows of stigmata are present, although the number in each row was not determined. Both apertures are on short anteriorly directed siphons with six-lobed apertures. The thoracic muscles are mainly longitudinal and they continue on to the abdomen in two strong, wide bands, one along each side of the ventral mid-line. The stomach is smooth-walled, and the gut loop wide.

The testis is a circle of about eight club-shaped follicles, the narrow ends converging in the centre of the circle where they join the vas deferens that extends toward the base of the atrial cavity between rectum and stomach and oesophagus. Neither eggs nor larvae were found in either specimen.

Remarks. The species is distinguished by its large globular spicules as well as the capsule of saucer-shaped ones. Spicule distribution is variable—the globular spicules crowded throughout the test in the present specimens, although Tokioka (1950) and Herdman (1886) found them only in the abdominal test, around the top of the abdominal capsule. Tokioka (1950) found them to be only 0.04 mm diameter, but of identical form to the variably sized spicules crowded throughout the newly recorded colonies.

The larva, incubated in a pouch at the top of the abdomen, has been described for C. hapu Monniot and Monniot, 1987 (see Monniot and Monniot, 2001). This species conforms with the present one in all its significant characters.

The oesophageal muscle found in the test of Cystodytes dellachiajei (see Kott, 1990a) has not been observed in the present specimens (in which the whole zooid is withdrawn from the thoracic space), although it may be present and obscured by the crowded globular spicules.

Cystodytes ramosus Kott, 1992 Cystodytes ramosus Kott, 1992b: 629 .

Distribution. New records: Queensland (Heron I, QM G307481; Swain Reefs, QM GH5731 G305480; Chauvel Reef, QM G315446; S. of Waining Reef, QM G304378). Formerly known only from the holotype, the new records demonstrate it to be a conspicuous and relatively common component of reef slope and inter-reefal habitats from 20 m and more (see Kott, 1992b).

Description. Colonies are tight complex masses (to 8 cm diameter) of thick, cylindrical branches (to 3 cm diameter), rounded terminally. Newly recorded colonies are larger but otherwise similar to the holotype (Kott, 1992b).