Eucoelium orientalis (Kott, 1990)

Kott, Patricia, 2006, Observations on non-didemnid ascidians from Australian waters (1), Journal of Natural History 40 (3 - 4), pp. 169-234: 189-190

publication ID 10.1080/00222930600621601

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Eucoelium orientalis (Kott, 1990)


Eucoelium orientalis (Kott, 1990)  

Polycitorella orientalis Kott 1990a, p 187   and synonymy; not E. orientalis: Kott 2003   .


Previously recorded (see Kott 1990a): Western Australia (Rottnest I., Houtman’s Abrolhos); Queensland (Swain Reefs, Heron I., Coral Sea). New records: Tasmanian Canyons (Banks Strait, 168 m)   .


Colonies are dome-shaped to stalked, with a single layer of moderately crowded spicules in the surface over an aspiculate layer of variable thickness. Spicules also are present internally in varying concentrations. Spicules are to 0.05 mm diameter with 5–13 stout conical rays in optical section. Large zooids open around the upper domed surface and converge toward the centre of the base of the colony. They are in a vegetative state, the abdomina breaking up into replicates.


Eucoelium   is known, from only eight species, from Japan, the Gulf of Suez and the western Indian Ocean, New Zealand, and tropical and temperate waters around the Australian continent (where three species are known). The present species has been recorded from the Great Barrier Reef and the Coral Sea, but the present record implies a wider range into temperate waters. All the known species of Eucoelium   are very variable, but can be distinguished by their spicules, those of the present species being to 0.05 mm diameter with 5–15 rays. Eucoelium mariae ( Michaelsen, 1924)   from New Zealand has smaller spicules than the present species and the principally temperate E. coronaria Monniot, 1988   has larger spicules and its zooids are arranged in conspicuous circular systems. Eucoelium orientalis: Kott 2003   has large (to 0.09 mm diameter) globular spicules as well as smaller stellate ones and appears not to be a synonym of the present species.

This genus and another polycitorid genus, Cystodytes   , are the only aplousobranch genera outside the Didemnidae   with the capacity to create calcareous spicules in the test. Although the spicules are very similar to those of the Didemnidae   , a phylogenetic relationship is not implied.

Like other species taken from the Tasmanian Canyons, the new record of the present species from so much further south than it was previously known provides further evidence that the Australian continent may constitutes a route for gene flow of shallow-water tropical species into temperate waters.

Eudistoma anaematum Kott, 1990  

( Figure 2G View Figure 2 )

Eudistoma anaematum Kott 1990a, p 196   .


Previously recorded (see Kott 1990a): Queensland (Great Barrier Reef). New record: Queensland (Bowden Reef, AIMS 17693).


The newly recorded colony has firm gelatinous test containing the usual long polycitorid zooids, which are arranged in circles with the long atrial siphons opening in the centre of the circle. Sand is not present either in or on the colony. The living colony was transparent and bluish beige. Dark, spherical pigment particles are scattered sparsely through the test of the preserved specimen. Zooids are robust, as previously described, with up to 30 stigmata in each of three rows and there is a long prestigmatal unperforated area in the pharynx. The almost spherical stomach is at the end of the long oesophageal neck, at the posterior end of the body. Zooids have up to two embryos developing in the atrial cavity. Larvae are similar to, although the trunk (0.75 mm long) is about half the length of the larval trunk of, E. globosum   . The three antero-median adhesive organs have wide platforms of adhesive cells on short thick stalks, each surrounded by a shallow epidermal cup; and three narrow, median, ectodermal ampullae alternate with the adhesive organs. A large oval yolk mass almost completely occupies the larval trunk. The tail winds about halfway around the trunk.


The species is distinguished from others in this homogenous genus by its naked, sand-free, translucent colony. Its larva is described here for the first time.














Eucoelium orientalis (Kott, 1990)

Kott, Patricia 2006

Polycitorella orientalis

Kott P 1990: 187

Eudistoma anaematum

Kott P 1990: 196