Oculinaria australis Gray, 1868

Kott, Patricia, 2005, Novel Australian Polyzoinae (Styelidae, Tunicata), Journal of Natural History 39 (32), pp. 2997-3011 : 3002-3003

Oculinaria australis Gray, 1868

( Figures 1D–H , 5B ) Oculinaria australis Gray 1868, p 564 ; Kott 1985, p 226 and synonymy.

Distribution

New records: Western Australia ( Warnboro ) ; South Australia (Kangaroo I., SAM E3267 ) ; Tasmania ( One Tree Point , QM G308760 ) ; New South Wales (Warren Head-Ulladulla, Sydney Harbour QM G304560 ) . Previously reported (see Kott 1985): Western Australia (Dongara, Wonerup, Cockburn Sound, Albany ) ; South Australia (Great Australian Bight, Wright I., West I.); Tasmania (Stanley); Victoria (Rams Head, off Lakes Entrance , Port Phillip Bay ) ; New South Wales (Port Jackson). Records of the species indicate a temperate species with a continuous range around the southern half of the continent.

Description

In situ photographs of the newly recorded specimen show it to have pink apertures showing through the sand. In preservative, it has a characteristic appearance, with the lower half of the zooids completely embedded in a solid basal mat of sandy common test and the anterior half of each zooid free and covered with thin, brittle, sand-impregnated test. The terminal free end of each zooid is more or less flattened, circular, with a small central four-lobed branchial aperture and is surrounded by a rounded marginal fold. The atrial aperture is a similar four-lobed aperture on the dorsal side of the free part of the zooid, behind the marginal fold that surrounds the flat anterior surface. Both apertures, especially the atrial one, are obscured by the sand embedded in the colony. A slight iridescence can be detected in the test around the apertures and lining the short siphons. This iridescence is caused by minute overlapping siphonal spines, their points directed toward the opening of the siphon. They have a slightly sinuous, curved profile, the pointed tip curving out and the posterior end of the base curving in. Near the base of the siphon the spines have a flattened, frayed posterior end and the base of the spine is completely open. Further up the siphon each side of the posterior end of the spine is closed in, meeting the opposite side in the midline and leaving only a small circular opening about halfway along the base, beneath the hollow terminal pointed projecting part of the spine. The spines are about 0.136 mm from the posterior end of the base to the terminal tip of the spine.

The body wall is delicate, with thin muscle bands radiating a short distance down the body, which is closely attached to the test. Crowded simple branchial tentacles are at the base of the branchial siphon. The duct of the neural gland has a simple opening on the dorsal tubercle. Four deeply curved branchial folds are in the branchial sac and the branchial formula is: E8(12)7(14)6(12)3(12)1DL. There are 8–10 stigmata per mesh. The gut, attached only very loosely to the body wall by few ligaments, forms a simple open loop diagonally across the posterior end of the left side of the body. The oesophagus is narrow and opens abruptly into the broad cardiac end of a pear-shaped stomach with about 28 internal folds. Gonads are not present on the left side of the body, but on the right up to seven long narrow straight ovarian tubes converge from around the ventral border toward the atrial aperture, which is about halfway down the dorsal surface in a concavity behind the bulge where the body forms a rim associated with the anterior marginal fold of the test. The long, narrow ovarian tubes have two rows of about 20 crowded male follicles per row beneath them and occasionally extending around their sides. Vasa efferentia extend around the sides of the ovary to join the vas deferens which runs along the centre of its mesial surface, opening at the base of the short oviduct.

Remarks

The siphonal armature and the position of the atrial aperture outside the anterior marginal fold are two of the most striking characteristics of this species but both were previously overlooked. Their presence has been confirmed in re-examined specimens from Victoria ( QM G9592 and G11857) .

Pyura tasmanensis Kott, 1985 has siphonal spines that resemble those in the present species both in size and shape, although their base is more closed in than those in the present species and they have a flange developed. Ctenyura tortuosa Kott, 1985 has similar but shorter spines and the spines in some Microcosmus species are also similar although their points are better developed and at a greater angle to the base. Certain species of the Styelinae also have siphonal armature but it is more often scales than spines. Scales are present in Styela spp. and a number of Cnemidocarpa spp. (see Kott 1985) although Cnemidocarpa intestinata Kott, 1985 and Polycarpa olitoria ( Sluiter, 1890) have spines. The only other species of Polyzoinae (besides the present one) known to have siphonal armature is Stolonica diptycha ( Hartmeyer, 1919) although it has scales rather than spines (see Kott 1985). It appears that no higher taxon level phylogenetic significance can be attached to either the form or the presence of siphonal armature.

Gonads of the present species suggest an affinity with Cnemidocarpa rather than most known species of Polyandrocarpa with their short, numerous, polycarp-type gonads. Polyandrocarpa abjornseni ( Hartmeyer and Michaelsen, 1928) is the only exception with two longish-oval gonads on each side of the body, although each has only six pairs of male follicles and is readily distinguished from the present species.

Figures

Figure 1. (A) Polyandrocarpa colemani (QM G308755): left and right pallial wall showing gut and gonads. (B, C) Polyandrocarpa colligata (QM G308758): (B) colony surface; (C) gut loop. (D–H) Oculinaria australis (SAM E3267): (D) portion of colony; (E) inner pallial body wall on right showing gonads; (F) inner pallial body wall on left showing gut and gonads; (G, H) siphonal spines. In (G), the open base of the spine in the centre of the light micrograph is showing; in all the other spines, only the hollow centres of the pointed tips are in focus. Scale bars: 1.0 mm (A); 2.0 mm (B, D–F); 0.2 mm (C); 0.05 mm (G, H).

Figure 5. In situ images. (A) Polyandrocarpa colemani (QM G308755) (photograph: Merrick Ekins); (B) Oculinaria australis (SAM E3267) (photograph: K. Gowlett Holmes); (C) Stolonica vermiculata (QM G308756) (photograph: Neville Coleman); (D) Botryllocarpa elongata (SAM E3232) (photograph: K. Gowlett Holmes).