Polysyncraton

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 : 1177-1179

publication ID	https://doi.org/ 10.1080/00222930801935958
persistent identifier	https://treatment.plazi.org/id/E8619D71-2D0A-4260-FE5B-FBFBFD96FBDC
treatment provided by	Felipe
scientific name	Polysyncraton
status

Treatment

Polysyncraton View in CoL ? palliolum Kott, 2001

( Figure 17B View Figure 17 )

Polysyncraton palliolum Kott 2001, p. 118 View in CoL .

Distribution

Previously recorded (see Kott 2001): Western Australia (Rottnest I.). New record: Western Australia CSIRO SS10 View Materials / 05 ( Jurien Bay , Stn 083, 113 m, 02.12.05, QM G328161 ) .

Description

The preserved colony is a scrap of an opaque white sheet with spicules crowded throughout. The surface is irregular and squashed, although occasionally there are traces of surface swellings with terminal common cloacal apertures. Zooids appear to be evenly distributed, the abdomina embedded in the basal test and the thoraces crossing the horizontal common cloacal cavity. Posterior abdominal cavities were not detected. Spicules are small (to 0.03 mm diameter) and most are stellate with 3– 15 almost fusiform rays drawn out into pointed tips but a few are burr-shaped with long rod-like rays with rounded or flattened ray tips.

Despite the fact that the form of the common cloacal systems was not determined, some zooids have particularly large anterior atrial lips with bidentate tips that appear to be like those found incorporated in the margin of large sessile common cloacal apertures in many species of this genus. Other zooids have small contracted atrial apertures with a small atrial lip from its upper margin and probably opened directly into the common cloacal cavity. The branchial apertures are on large tulip-shaped siphons with six conspicuous lobes around the margin of the opening. Thoraces are relatively large with four rows of stigmata and about 15 stigmata per half row. Four or five male follicles were observed in some of the zooids but, although the distal part of the vas deferens was observed extending anteriorly, its possibly coiled proximal part was not detected. In most of the zooids a large yellow egg is present at the posterior end of the zooids against the ventrally flexed part of the gut loop. A retractor muscle was not detected.

Remarks

The characters that, together, support the assignation of this specimen to the genus Polysyncraton are the large tulip-shaped branchial siphon, the large thorax with numerous stigmata in each row, the large bidentate atrial lip, the four or five testis follicles and the large yellow egg tightly held against the ventral flexure of the gut loop at the posterior end of the zooid. The burr-like spicules and the zooids closely resemble those of a number of species of this genus. In particular, P. purou Monniot C. and F., 1987 (from the western Pacific), P. palliolum Kott, 2001 (from Rottnest I., WA) and P. regulum Kott, 2001 (from Queensland) have similar but larger spicules (0.07 mm, 0.06 mm and 0.1 mm diameter, respectively). Polysyncraton dromide Kott, 2001 from Cockburn Sound and tropical Australian waters has similar common cloacal systems and spicules although, like the present specimen, the spicules, are smaller (to 0.04 mm diameter). It is distinguished from both P. palliolum and the present specimen by the absence of spicules from parts of the colony. Geographically, the present specimen has an affinity with both P. palliolum and P. dromide . Although its common cloacal systems together with its smaller spicules could distinguish it from other known species of Polysyncraton , it is questionably assigned to P. palliolum until additional data from better specimens become available.

Polysyncraton pavimentum Monniot, 1993 View in CoL

( Figures 13H View Figure 13 ; 17C View Figure 17 )

Polysyncraton pavimentum Monniot 1993, p. 9 View in CoL . Not Kott 2002c, p. 32 ( P. polysystema Kott, 2005a, p. 2435 View in CoL ).

Distribution

Previously recorded (see Monniot 1993): New Caledonia, Chesterfield Reef. New record: Western Australia CSIRO SS10/05 (Kalbarri, Stn 99, 252 m, 04.12.05, QM G328165: Kalbarri, Stn 102, 96 m, 05.12.05, QM G328058-9; Zuytdorp, Stn 104, 97 m, 05.12.05, QM G328168).

Description

Colonies are extensive, thin, brittle, whitish sheets with a smooth surface. Spicules are crowded throughout. They are to 0.08 mm diameter and are of two sorts, some stellate with 13–15 sharply pointed conical rays in optical transverse section, and others are burr-like, their flat-tipped rays made up of crowded, parallel, rod-like crystals. Zooids are robust, with a long cylindrical branchial siphon. Separate common cloacal systems, each a circle of zooids about seven deep around a central stellate common cloacal aperture, are separated from one another by a band of solid test (visible on the surface of the colony) that divides it into polygonal areas. The position of the zooids is indicated by the stellate branchial apertures, their margins lined with spicules, opening on the surface of the colony. Zooids are small but robust with a conspicuous tulip-shaped branchial siphon, a thin, narrow anterior atrial lip and six or seven stigmata in each half row. The simple gut loop does not appear to be bent ventrally. Gonads were not detected.

Remarks

Although the gonads were not detected in this specimen, it has been assigned to this genus on the basis of its separate cloacal systems (known to occur in a number of Polysyncraton spp ), large branchial siphons, thin, narrow atrial tongues and the size and form of its spicules.

Of the tropical species of this genus known to have spicules to 0.09 mm diameter and separate systems, Polysyncraton polysystema Kott, 2005a from the Northern Territory ( P. pavimentum: Kott 2002c ) has stellate spicules with fewer rays than P. pavimentum Monniot, 1993 (from New Caledonia) which, like the present specimen, has two sorts of spicules, some globular with flat-tipped rays and others stellate with 13–15 pointed rays. Polysyncraton glaucum Kott, 2001 (from the Great Barrier Reef) has long conical spicule rays, P. lithostrotum: Monniot 1993 from New Caledonia ( Polysyncraton sp. ?) has spicules with short rays to only 0.04 mm diameter (see Kott 2005, p. 2436) and P. multiforme Kott, 2001 (from Houtman’s Abrolhos) has stellate spicules (to 0.05 mm diameter) with numerous (17–19) short pointed rays.