Homoeodistoma omasum, Monniot, 1987

Monniot, Françoise, 2012, Some ascidians from the southern coast of Madagascar collected during the “ AtimoVatae ” survey, Zootaxa 3197, pp. 1-42 : 20-22

publication ID

https://doi.org/ 10.5281/zenodo.246182

DOI

https://doi.org/10.5281/zenodo.4893781

persistent identifier

https://treatment.plazi.org/id/3055E11F-FF83-FF84-71A5-CA46FBC269B2

treatment provided by

Plazi

scientific name

Homoeodistoma omasum
status

 

Homoeodistoma omasum ? Monniot, 1987

( Figure 17 View FIGURE 17 )

Homoeodistoma omasum Monniot F., 1987: 503 fig. 2C–E pl. 1B, New Caledonia. Monniot & Monniot: 2008 View Cited Treatment : 831 View Cited Treatment figs 45; 76E, New Guinea.

Stations. TR 1 (MNHN: A1 HOM 10). TA 25 (MNHN: A1 HOM 11)

Bellona Island, Salomon Islands, 11° 51.086 S –159° 27.617 E, 10m, 20/04/2002, P. Laboute col. (MNHN: A1 HOM 7)

The colonies are sandy, made of thick lamellae or polygonal lobes united at their base ( Fig. 17 View FIGURE 17 A). The zooids apertures are lined on the sides of protruding rims located at the outline of a colony lobe, or along convoluted pads in colonies with several systems. Both siphons are long ( Fig. 17 View FIGURE 17 D) with red longitudinal stripes (the colour progressively disappears in formalin).Their rim is dentate and a strong sphincter encircles their base. The musculature of the thorax is dense with thin longitudinal and transverse fibres regularly crossed ( Fig. 17 View FIGURE 17 D). The branchial sac ( Fig. 17 View FIGURE 17 B) has from 17 to 21 elongated stigmata crossed by parastigmatic vessels. There are no papillae on the transverse vessels. A constriction separates the thorax from the abdomen. The stomach has a smooth wall. It is followed by a narrow segment and farther the intestine widens in a part whose wall shows an areolation ( Fig. 17 View FIGURE 17 C) which becomes obvious only after staining. The rectum begins with 2 caeca and is straight until the base of the thorax. The anus has 2 lobes. The post-abdomen is long with an anterior ovary followed by a double line of testis vesicles limited to the first half of the post-abdomen length. The larvae, 1.8mm long, have 3 well divergent adhesive papillae and a very large anterior cap of numerous vesicles on each side.

The morphology of the colonies and zooids is the same as in the type material from New Caledonia and also corresponds to the material from Bellona (Solomon I.). The specimens identified by Monniot & Monniot (2008) from Papua New Guinea differ by the absence of parastigmatic vessels on the branchial sac; all other characters are similar, the larva has the same structure but is a somewhat smaller.

It is likely that several species of Homoeodistoma exist, but no striking characters are obvious allowing to separate them, their particularities are given in Monniot & Monniot (2008). Kott (1992) groups in a new monospecific genus Condominium several species of Homoeodistoma : Placentela areolata Kott, 1963 and Placentela ellistoni Kott 1972 whose type was reexamined ( Monniot & Monniot 2008). Kott’s genus is not retained here.

The genus Homoeodistoma is recorded here for the first time from the Indian Ocean.

Kingdom

Animalia

Phylum

Chordata

Class

Ascidiacea

Order

Enterogona

Family

Polyclinidae

Genus

Homoeodistoma

Loc

Homoeodistoma omasum

Monniot, Françoise 2012
2012
Loc

Homoeodistoma omasum

Monniot 2008: 831
Monniot 2008: 2008
Monniot 1987: 503
1987
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