Diazona fungia Monniot F., 2001

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 : 1955-1957

Diazona fungia Monniot F. and C., 2001

( Figure 1A–B )

Diazona fungia Monniot F. and C., 2001, p. 291.

Distribution

Previously recorded ( Monniot F and Monniot C 2001): Fiji, Vanuata, 53 m. New record: CSIRO 05 / 07, western Australia (Station 029-047, Dampier, 19.79 S 115.47 E, 108 m, Beam trawl, 12.6.07 – three specimens QM G328570 ) .

The new record significantly extends the known depth range of this species.

Description

Although the type colonies of this species are said to be “massive and pedunculate” their actual measurements are similar to the newly recorded colonies (2–3 cm and 3–4 cm diameter heads). Zooids open independently to the flattened upper surface. In the preserved colonies the zooids are only slightly visible through the almost opaque, tough, white test. The diameter of the colony is reduced and the consistency of the test becomes harder toward the base.

Zooids are very contracted and firmly embedded in the tough test. Often they are withdrawn from the surface into the centre of the colony and toward the base. Strong longitudinal muscle bands that extend along each side of the thorax and the abdomen surround them. Transverse muscles were not detected. Both apertures are on relatively long siphons at the anterior end of the body and appear to have the rims lined with six long lobes (although these are obscured and often mutilated in removing the zooids from the test). Long, simple tentacles are at the base of the branchial siphon and project well down into the branchial sac. About 25 rows of at least 30 stigmata in each half row are in the branchial sac but it is so contracted that these numbers cannot be considered reliable. Also, the internal longitudinal vessels, which in some places appear to be present, are generally completely obscured by contraction. The abdomen is about three times the length of the thorax and consists of a moderately long oesophagus, a large stomach clearly marked with characteristic crowded, parallel, longitudinal ridges is in the middle third of the posterior half of the descending limb of the gut loop and the rectum is a wide cylindrical tube occupying the whole of the distal (ascending) limb of the gut loop. Gonads, consisting of a large egg and a diffuse mass of male follicles are in the loop of the gut.

Remarks

Despite their contracted condition, which has obscured many of the more significant characters of the zooids, these specimens have been assigned on the basis of the shape

of the colonies, the large number of rows of stigmata, the form of the stomach and the striations in its wall and the length of the abdomen.

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.