Aplidium phortax ( Michaelsen, 1924 )

Page, M. J., Willis, T. J. & Handley, S. J., 2014, The colonial ascidian fauna of Fiordland, New Zealand, with a description of two new species, Journal of Natural History (J. Nat. Hist.) 48 (27 - 28), pp. 1653-1688 : 1672-1673

Aplidium phortax ( Michaelsen, 1924)

( Figure 7F )

Amaroucium phortax Michaelsen, 1924: p. 389 –400, figs 20, 21.

Aplidium (Amaroucium) phortax . Brewin, 1946: p. 92 –94, fig. 2.

Aplidium phortax Millar, 1982: p. 22 , fig. 9.

Material examined

New records: Fiordland, Awash Rock, Long Sound (43° 03.937’S, 166° 41.013’E, 15 m, 28 January 2009, NIWA 49947 , one colony); Bluff Harbour, Tiwai Point (46° 35.523’S, 168° 21.137’E, 7–10 m, 20 August 2007, MNP9168 , two colonies); Pelorus Sound, Capsize Point mussel farm (41° 05.355’S, 173° 55.940’E, 10 m, 2 March 2004, MNP7367 , one colony) .

Previously recorded: New Zealand, Tauranga ( Michaelsen 1924); d’ Urville Island ( Sluiter1900, as Amaroucium ritteri ); Otago ( Brewin 1946); Stewart Island ( Michaelsen 1924); Chatham Islands ( Sluiter 1900, as Amaroucium obseum ); eastern Australia and Solomon Islands ( Kott 1963).

Description

Colonies vary in colour from cream to light pink (YR 8/4, NIWA 49947). They can reach a relatively large size, often exceeding 200 mm diameter, and have a firm thick (<20 mm) fleshy test free of sand. Zooids are packed tightly into elongate oval systems around meandering common cloacal canals that radiate out and anastomose from indistinct cloacal apertures ( Figure 7F ). The colonies generally follow the substratum, occasionally forming low slightly raised lobes. Zooids are long and thin and the abdomen and thorax are of equal length measuring approximately 3 mm, and the long narrow post-abdomen 11 mm. The post-abdomens are densely interwoven in the test below. The atrial aperture is small and surmounted by a stout triangular lappet. The branchial sac has 11 rows of 10 stigmata per side in our specimens, fewer than the 12–13 rows of 10–11 stigmata per half row described by Brewin (1946). The stomach is barrelshaped with 25–30 rows of discontinuous folds. Larvae were not present in the Fiordland specimens. Testis follicles form a double row in the posterior half of the post-abdomen and the ovary lies at the anterior end above the follicles.

Remarks

The Aplidium phortax colony from Fiordland is consistent with those collected from Bluff (MNP9168) and Pelorus Sound (MNP7367). The morphology closely matches colonies described by Brewin (1946) and the zooids have characteristically more than 25 stomach folds and a long narrow post-abdomen with testis lobes in a double row.

Figures

Figure 7. In situ images of: (A) Synoicum occidentalis (NIWA 49972); (B) Synoicum stewartense (NIWA 49984). (C) Aplidium benhami (NIWA 49993,); (D) Aplidium coronum sp. nov. (NIWA 60890); (E) Aplidium coronum sp. nov. (NIWA 49995, holotype); (F) Aplidium phortax (NIWA 9947).