Polysyncraton polysystema, Kott, 2005

Kott, Patricia, 2005, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (Part 3), Journal of Natural History 39 (26), pp. 2409-2479 : 2435-2436

Polysyncraton polysystema sp. nov.

Polysyncraton pavimentum: Kott 2002a, p 32 . Not Monniot 1993, p 9.

Distribution

Previously recorded (see Kott 2002a): Northern Territory (Darwin Harbour). Type locality: Northern Territory (Darwin Harbour, Plater Rock, 8–10 m, coll. K. Gowlett Holmes, 21 November 1999, holotype NTM E170 ). The previously recorded specimen is from the type locality .

Remarks

Although their colonies are similar and their spicules are the same size, P. pavimentum: Kott, 2002a and P. pavimentum Monniot, 1993 from Chesterfield Reef and New Caledonia appear not to be conspecific. The nominal species has 13–15 pointed rays in optical

Figure 5. (A–C) Polysyncraton papyrus (SAM E3253): (A) colony; (B) thorax; (C) gut loop. (D–F) Polysyncraton pedunculatum (SAM E3272): (D) colony (E) thorax, (F) abdomen. Scale bars: 1.0 mm (A); 0.1 mm (B, C, E, F); 1.0 cm (D).

transverse section, while those of the new species have only 9–11 conical, pointed or truncated rays in optical transverse section.

Polysyncraton lithostrotum: Monniot, 1993 and P. pavimentum Monniot, 1993 , both from Chesterfield Reef and New Caledonia, have similar stellate spicules with 13–15 pointed rays in optical transverse section and some globular spicules, six coils of the vas deferens, a small retractor muscle, similar larvae with the larval trunk 0.7–0.8 mm long, and a circle of 24 larval epidermal ampullae. However, Kott (2001) was wrong in thinking them synonymous, for, despite their very similar appearance, the maximum diameter of spicules of P. lithostrotum: Monniot, 1993 is only 0.04 mm —half the size of the largest spicules in P. pavimentum Monniot, 1993 . Further, the New Zealand species, P. lithostrotum (Brewin, 1956) is distinguished from the tropical P. lithostrotum: Monniot 1993 by its larger spicules with rounded rays. It is probable that P. lithostrotum: Monniot 1993 is another undescribed species in this related group, with a maximum spicule diameter of 0.04 mm and pointed spicule rays—different from the large spicules with rounded rays of the New Zealand species.

It appears that the scale line of 0.1 mm applied to the larvae of P. lithostrotum: Monniot, 1993 is incorrect, the larval trunk being reported as 0.8 mm long but measuring 1.6 mm ( Monniot 1993, Figure 1F ).

Figures

Figure 1. (A, B) Leptoclinides frustus sp. nov. (SAM E3255, holotype): (A) vertical section through a common cloacal canal (semi-diagrammatic); (B) zooid. (C) Leptoclinides lissus (QM G308709): larva. Scale bars: 0.5 mm (A); 0.1 mm (B, C).