Polysyncraton dealbatum, Kott, 2008

Kott, Patricia, 2008, Ascidiacea (Tunicata) from deep waters of the continental shelf of Western Australia, Journal of Natural History 42 (15 - 16), pp. 1103-1217 : 1172-1174

publication ID	https://doi.org/ 10.1080/00222930801935958
persistent identifier	https://treatment.plazi.org/id/E8619D71-2D07-4265-FE06-FB21FD60FB3F
treatment provided by	Felipe
scientific name	Polysyncraton dealbatum
status	sp. nov.

Treatment

Polysyncraton dealbatum View in CoL sp. nov.

( Figures 13A View Figure 13 , 16G View Figure 16 )

Distribution

Type locality: Western Australia, CSIRO SS10 View Materials / 05 (Shark Bay, Stn 112, 112.8230E 25.9076S, 100 m, 6 December 2005, holotype WAM Z27527 View Materials , QM G 328119 ) GoogleMaps .

Description

The holotype is part of an encrusting colony, white in preservative, with the spicules crowded throughout. Zooids are arranged along each side of shallow, thoracic, circular common cloacal canals and occasionally sessile common cloacal apertures are at the junctions of these canals. A layer of surface test containing the thoraces is relatively thin and even while the thicker basal layer of test is uneven, extending into irregularities in the substrate. Spicules are burr-like, to 0.05 mm diameter, with crowded elliptical or club-shaped rays. Zooids are contracted. A muscular atrial tongue projects from the upper rim of the sessile, open atrial aperture which exposes most of the branchial sac to the common cloacal cavity. A short, contracted retractor muscle projects from the postero-ventral corner of the thorax. About 10 stigmata on each side were detected in the fours rows in the branchial sac. The gut appears to be voluminous, with a large spherical stomach and posterior stomach. It is obscured by a clump of seven or eight testis follicles crowded against the ventrally flexed part of the gut loop. The three coils of the vas deferens are on the surface of the testis and a large yellow egg projects from the side of the abdomen.

Larvae are being incubated in the basal test. The larval trunk is 1.3 mm long. Each of four primary lateral ampullae subdivides to form eight ampullae on each side of the three antero-median adhesive organs. A large, external horizontal lateral ampulla projects back from just behind the adhesive array on the left side of the larva. Four rows of stigmata are in the larval oozooid and in each of two thoracic blastozooids. The tail winds two-thirds of the way around the trunk.

Remarks

Although the zooids are so contracted, the generic characters of Polysyncraton can all be detected, viz. the numerous testis follicles, the four rows of stigmata in the larval oozooid that distinguish it from Trididemnum and Didemnum and the open, sessile atrial aperture, retractor muscle and larval blastozooids that exclude it from Leptoclinides .

In the genus Polysyncraton there are many species with similar common cloacal systems and similar spicules absent from some parts of the colony. These include P. arvum Kott, 2004c and P. purou C.and F. Monniot, 1987 (with larger spicules), P. reticulatum Kott, 2004b and 2007, and P. dromide Kott, 2001 (with smaller spicules). Similar but smaller larvae, with the four subdividing primary lateral ampullae on each side and two larval blastozooids, are present in P. regulum Kott, 2001 and P. rubitapum Kott, 2001 . Polysyncraton pseudorugosum Monniot, 1993 has stellate rather than burr-like spicules, deeper common cloacal canals and more larval ampullae (12 per side) than the present species. Nine vas deferens coils in P. palliolum Kott, 2001 distinguishes it from the present species.