Sigillina cyanea ( Herdman, 1899 )

Kott, Patricia, 2007, Taxonomic affinities of three stalked colonial species of the Ascidiacea (Tunicata) from the central coast of New South Wales and indications of a trans-Tasman connection, Journal of Natural History 41 (9 - 12), pp. 633-645 : 643-644

Sigillina cyanea ( Herdman, 1899)

Figure 3C

Colella cyanea Herdman 1899, p. 70 (syntypes AM U153 , U346 ).

Sigillina cyanea: Kott 1990, p. 89 and synonymy.

Distribution

Previously recorded (see Kott 1990). Western Australia (the Dampier Archipelago and the Montebello Is and south to North West Cape and Exmouth Gulf, Shark Bay , Houtman’s Abrolhos, Dongara, Cockburn Sound, Cape Naturaliste, King George’s Sound) ; New South Wales (Port Hacking, Port Jackson , Arrawarra, Nambucca Heads); Aru Is .

New record. New South Wales (Port Stephens, QM G 308882; Port Macquarie and Coffs Harbour, fide N.Coleman).

Description

Colonies are dark blue to purple and are relatively hard in preservative. The thick stalk is about 1.5 cm in diameter, and the head slightly wider, to 2 cm. The branchial sac has an extensive pre- and post-stigmatal area of unperforated pharyngeal wall. About 20 long, narrow stigmata are in each of the three rows. About 10 fine longitudinal muscles extending from the short siphons (close to one another at the anterior end of the zooid), along each side of the thoraces, the relatively short abdomina and the long vascular stolons extend down into the base of the stalk parallel to one another. Transverse muscles were not detected. Both colony and zooids of this species are as previously described (see Kott 1990)

Remarks

The genus Sigillina contains species with cushion-like encrusting, or massively lobed, or small flat-topped colonies and only three are reported to be stalked like the present species. One stalked species, S. mjöbergi Hartmeyer, 1919 is distinguished by a number of characters including its remarkable larvae with tubular adhesive organs (see Kott 1990). The other stalked species known, the type of the genus Sigillina australis Savigny, 1816 , resembles the present one in most respects, although the colour of S. cyanea readily distinguishes it. Kott (1990) thought the number of stigmata was a distinguishing character, but these seem to vary between 20 and 30 in each of the species. Further, transverse thoracic muscles have not been detected in either, although there are a few in other species of the genus. Larvae of both these stalked species are large and have only two large adhesive organs in the antero-median line, although the present species has a larger (up to 3.3 mm long) trunk, sessile adhesive organs and lateral ampullae have not been detected (see Kott 1990) while the larvae of S. australis have a trunk to 2 mm long, thickstalked adhesive organs with long, narrow, adhesive areas and lateral ampullae around their base.

The nudibranch, Nembrotha sp. is reported in a commensal or predatory relationship exclusively on specimens from Port Stephens, Port Macquarie and Coffs Harbour.

Figures

Figure 3. In situ colour images: (A) Euclavella claviformis; (B) Hypsistozoa distomoides colony lying flat on the sea floor at low slack tide; (C) Sigillina cyanea from high-energy location, showing tip of colony worn by abrasion on sea floor sediments. The possibly commensal nudibranch Nembrotha sp. is associated with the colony.