Diazona textura Monniot C., 1987

Kott, Patricia, 2009, Taxonomic revision of Ascidiacea (Tunicata) from the upper continental slope off north-western Australia, Journal of Natural History 43 (31 - 32), pp. 1947-1986 : 1957

Diazona textura Monniot C., 1987

( Figure 1C ) Diazona textura Monniot C., 1987, p. 4 . Monniot F. and C. 2001, p. 293 and synonymy?> D. tenera Monniot F. and C. 1996, p. 226; 2001, p. 293).

Distribution

Previously recorded ( Monniot F and Monniot C 2001): Micronesia, Indonesia, New Caledonia, Philippines. New record: CSIRO 05 / 07 western Australia (Station 125-060, Lacepede, 15.81 S 121.16 E, 90 m, Sled tow, 1.7.07, QM G328571 ) .

Description

The present specimen is a scrap of a colony consisting of a horizontal, almost cylindrical, basal mass of firm, translucent test with a rough surface, from which arise two vertical branches about 3 cm long, one subdivided terminally. The test on the base and on the upright branches is the same with the exception only of the terminal part of each lobe, which has soft, transparent, thin, flexible test that is mutilated in this specimen.

Traces of a number of zooids are present in each lobe extending in parallel down towards the cylindrical base. Six well-formed lobes are present around each of the apertures. About 20 crowded rows of stigmata are in the branchial sac. At least 12 internal longitudinal vessels supported by papillae can be seen to extend the length of the branchial sac. However, neither the stomach nor the gonads were detected and the structure of the zooids is largely obscured by contraction and mutilation.

Remarks

The colony superficially resembles Polycitor circes Michaelsen, 1930 in the Polycitoridae , which has vertical lobes with terminal transparent test in which zooids are completely embedded. The latter species also resembles Clavelina arafurensis, Millar (1975 ; p. 208) remarking that: “it is disturbing to note the similarity between the present material and Clavelina arafurensis Tokioka , whose colony is almost identical and whose zooids differ mainly in the possible smooth-rimmed siphons and the apparent absence of longitudinal thoracic muscles”. The delicate, elastic thoracic test of the present specimen differs from the test in which the polycitorid zooids are embedded. However, although the colony resembles Clavelina arafurensis in consistency, the zooids of the present specimen have six-lobed apertures that, together with the size of the branchial sac and the presence of internal longitudinal branchial vessels (of which traces were detected), indicate that the specimen belongs to Diazona .

A few Diazona spp. have some part of the zooids projecting from the surface of the colony ( D. formosa and D. textura ; see Key earlier) and although the zooids of the present specimen are not seen to project, the test in the terminal part of the lobes is certainly soft and very mutilated and in living specimens the zooids may well be found to project separately from the top of the lobe. Those Diazona spp. with completely embedded zooids have smooth firm test throughout, rather than the delicate, transparent head of the species to which this specimen is assigned.

Figures

Figure 1. (A–B) Diazona fungia (QM G328570); (A) colony; (B) zooid. (C) Diazona textura (QM G328571) colony. (D) Polycitor translucidus (QM G328573) colony. (E–F) Sigillina mjöbergi (QM G328563); (E) colony; (F) zooid. Scales: A, C, D, 0.5 cm; B, 1.0 mm; E, 1.0 cm; F, 0.5 mm.