Aplidium benhami ( Brewin, 1946 )

Page, M. J., 2018, Colonial ascidians from the Foveaux Strait region of New Zealand, Journal of Natural History (J. Nat. Hist.) 52 (17 - 20), pp. 1157-1180 : 1171-1172

Aplidium benhami ( Brewin, 1946)

( Figure 6d )

Aplidium (Amaroucium) benhami Brewin, 1946: 95–97 , fig. 4, pl. 2, figs 1, 4, pl. 3, fig. 3, pl. 5, fig. 1. Amaroucium benhami Brewin, 1956: 122 ; 1958a: 439; 1960: 119.

Material examined

New records. NEW ZEALAND, Bluff Harbour , Tiwai Point (46°35.52 ʹ S, 168°21.14 ʹ E, wharf pile, coll. M. Page, 9 m, 20 August 2007, NIWA68101 ); Tiwai Point (46°35.51 ʹ S, 168° 21.15 ʹ E), wharf pile, coll . L . Peacock, 6 m, 10 February 2011, NIWA84207 .

Previously recorded. New Zealand, South Island; Portobello Peninsula ( Brewin 1946); Chatham Islands ( Brewin 1956); Stewart Island ( Brewin 1958a); Cook Strait ( Brewin 1960); Fiordland ( Page et al. 2014).

Description

Colonies of Aplidium benhami collected off wharf piles in Bluff Harbour are relatively large, compared to specimens sampled from natural substrata in more exposed environments. They are bright orange (5YR12), cushion-shaped, firm gelatinous colonies measuring up to 100 mm in greatest diameter. The branchial apertures of the zooids are pigmented white, standing out against bright orange thoraces, and a lightly pigmented orange test ( Figure 6d ). Unlike the small colonies from other regions, the zooids are arranged in parallel rather than stellate systems, and common cloacal apertures are not obvious.

The zooids are stout, measuring 7 mm total length, with a thorax and abdomen of approximately equal length and a post-abdomen 3 mm long. The branchial aperture has low indistinct lobes, and the small atrial aperture is surmounted by 3 short atrial lappets. Three embryos are sequentially developed in the atrial brood pouch. The larval characters are as described in Page et al. (2014). Also noted in the present specimen is the orange pigmentation of the branchial sac.

Remarks

The Tiwai Point A. benhami colonies closely resemble the Otago Harbour holotype in colour and zooid morphology ( Brewin 1946). Furthermore, larval characters are the same for this species as described from Fiordland ( Page et al. 2014).

Figures

Figure 6. In situ images of: (a) Diplosoma velatum (NIWA68092); (b) Polyclinum novaezealandiae (NIWA68097); (c) Synoicum stewartense (NIWA68089); (d) Aplidium benhami (NIWA68101); (e) Aplidium knoxi (NIWA68091); (f) Aplidium phortax (NIWA68109).