Aplidium benhami ( Brewin, 1946 )

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 : 1668-1669

Aplidium benhami ( Brewin, 1946)

( Figures 9 , 7C )

Aplidium (Amaroucium) benhami Brewin, 1946: p. 95 –97, fig. 4, pl. 2, figs 1, 4, pl. 3, fig. 3, pl. 5, fig. 1.

Amaroucium benhami Brewin, 1956a: p. 122 ; 1958a: p. 439; 1960: p119.

Material examined

New records: Thompson Sound, Crayfish heights (45° 13.182’S, 166° 58.656’E, 3–10 m, 30 January.2006, NIWA 49993 ) .

Previously recorded: New Zealand, South Island; Portobello Peninsula ( Brewin 1946), Chatham Islands ( Brewin 1956a), Stewart Island ( Brewin 1958a) and Cook Strait ( Brewin 1960).

Description

Aplidium benhami has characteristic small orange vase-shaped colonies arising from a short narrow stalk. The colony heads, approximately 30 mm high, can be joined at their base to form diffuse aggregations in a larger colony ( Figure 7C ). The hemispherical tops of the colony heads contain up to 60 zooids in a soft, sand-free gelatinous test. The orange zooids form stellate systems around indistinct common cloacal apertures. The rim of zooid branchial apertures is pigmented white and the atrial aperture surmounted by three lappets, the central one being the longest of the three. Zooids measure approximately 9 mm long, and the post-abdomen encompasses half of the total length ( Figure 9A ). The branchial sac has 11 rows of 12–13 stigmata per half row. The stomach is barrel-shaped with 23–29 discontinuous folds. Testis follicles occur in paired rows in the posterior threequarters of the post-abdomen and the ovary lies above at the anterior end. Bright orange embryos are crowded in the atrial cavity, which is bulged into a brood pouch to accommodate the large larvae, 0.85 mm in trunk length ( Figure 9B ). The larvae have three slender median ampullae alternating between three adhesive papillae arranged along the median line and four short lateral ampullae each side ( Figure 9C ).

Remarks

Fiordland species closely resemble the type specimen from Otago ( Brewin 1946) in colour, colony and zooid morphology. However, Brewin did not note the presence of a brood pouch, or show detail of the arrangement of ampullae on lateral and median sides of the tadpole. The 3.4 mm long tadpole measured by Brewin is significantly greater than the trunk length of larvae from our material (0.85 mm). Brewin’ s measurement probably referred to the total larval length. Aplidium larvae are generally less than 1.0 mm trunk length with few exceptions; e.g. Kott (1992) named Aplidium magnilarvum Kott, 1992 after the large 2 mm long larva (trunk length).

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).

Figure 9. Aplidium benhami (NIWA 49993): (A) orange zooid with developing larvae in the peribranchial cavity; (B) larva showing orange pigmentation; (C) larva showing structure of adhesive papillae and lateral ampullae; scale bars: A, B, 1 mm; C, 0.5 mm.