Polysyncraton pseudomagnetae, Kott, 2010

Kott, Patricia, 2010, New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (part 2), Journal of Natural History 38 (26), pp. 2455-2526 : 2483-2484

Polysyncraton pseudomagnetae sp. nov.

( figure 17E )

Distribution. Type locality: Northern Territory (Darwin, Angler Reef, 10–12 m, coll. B. Glasby and party, 31 August 2002, holotype QM G308612).

Description. The colony is a hard sheet mottled white and grey. Spicules are in the surface sometimes, especially over the common cloacal canals, mixed with black pigment particles. Also, there are aggregations of black pigment in the base of the colony. Zooids are along each side of the common cloacal canals that surround white zooid-free areas. White spicules are crowded throughout the colony and can be seen through the open common cloacal apertures, which expose the base of common cloacal cavity. In some parts of the colony the common cloacal canals expand into horizontal spaces, penetrating in amongst the thoraces, isolating them from one another, each with a ventral strip of test. Spicules are to 0.06 mm diameter and are of two types, some with pointed and others with flat-tipped rays. Spicules have 15–17 rays in optical transverse section.

Zooids have a long thorax with eight stigmata in the anterior row, a short retractor muscle from the top of the oesophageal neck, a short, bifid atrial tongue and five coils of the vas deferens around four or five testis follicles.

Remarks. This species has the same range of spicules as P. magnetae Hastings, 1931 and similar systems. However, the spicules are larger, the retractor muscle projects from the top of the oesophageal neck rather than from some way down it, and the present species has more coils of the vas deferens, P. magnetae having only three coils. Polysyncraton longitubis from South Australia has similar but smaller spicules with fewer rays and more coils of the vas deferens; and P. millepore Vasseur, 1968 has slightly smaller spicules, also with fewer rays.

Polysyncraton pseudorugosum Monniot, 1993

( figure 17F )

Polysyncraton pseudorugosum Monniot, 1993: 10 ; Kott, 2001: 123; 2002c: 33.

Distribution. Previously recorded (see Kott, 2001, 2002c): Queensland (Hervey Bay); Northern Territory (Darwin, Bathurst I.); Coral Sea. New records: Northern Territory (Darwin, Angler Reef, QM G308598, Stevens Rock, QM G308600).

Description. Both newly recorded colonies are flat lamellae, orange in life, with rounded margins produced out into short, rounded to cylindrical lobes. The colonies are hard and greenish yellow in preservative and the preservative is the same colour. Firm pillars of solid test extend through the depth of the colony, and are surrounded by circular common cloacal canals lined on each side by zooids, the ventral surfaces of the thoraces embedded in the pillars of solid test and the abdomina bent around into the layer of spicule-free test that lines the base of the common cloacal canals. The surface of the colony is depressed over the common cloacal canals. Spicules are large, to 0.09 mm diameter, stellate, with 9–11 conical, pointed rays and they are present throughout the colony except for the thin aspiculate layer of test lining the common cloacal canals.

Zooids have a wide atrial aperture exposing most of the branchial sac directly to the common cloacal cavity and reducing the parietal body wall to a narrow strip along each side of the endostyle. Seven stigmata are in the anterior row. The vas deferens coils four times. Larvae are present in the basal test. The trunk is deep, 0.7 mm long with up to 12 lateral ampullae on each side of the antero-median adhesive organs. There is at least one blastozooid.

Remarks. The newly recorded colonies of this well-characterized species are as previously described. The common cloacal canals, and the thin layer of aspiculate test lining them occur also in Polysyncraton peristroma , but the species have different spicules and are a different colour. The spicules resemble those of P. cuculliferum but are larger and they do not become sparser toward the base of the colony as they do in P. cuculliferum . The spicules that most closely resemble those of the present species are those of P. montanum , which is distinguished from the present species principally by the upright conical colony, as opposed to the hard, flattened lamellae of the present species.

Figures

FIG. 17. (A) Polysyncraton galaxum (SAM E2927); (B) Polysyncraton longitubis (SAM E2929); (C) Polysyncraton montanum (SAM E3224); (D) Polysyncraton peristroma (QM G308608); (E) Polysyncraton pseudomagnetae (QM G308612); (F) Polysyncraton pseudorugosum (QM G308600); (G) Polysyncraton reticulum (SAM E2917); (H) Polysyncraton rica (SAM E3216).