Polyclinum novaezelandiae Brewin, 1958a

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 : 1170

Polyclinum novaezelandiae Brewin, 1958a

( Figures 6b , 7a–c )

Polyclinum novaezelandiae Brewin, 1958a: 442 ; Millar 1982: 43.

Material examined

New records. NEW ZEALAND, Bluff Harbour , Tiwai Point (46.591°S, 168.349°E, 10 m, 31 August 2007, NIWA68097 , 1 colony; 46.591°S, 168.349°E, 6 m and 7 February 2011, NIWA87159 , 2 colonies) .

Previously recorded. New Zealand, Foveaux Strait ( Brewin 1958a).

Description

Colonies of this species are large hemispherical cushions reaching 100 mm in greatest diameter and 50 mm high, attached to the substratum by most of their base. Numerous relatively tall (3 mm long), cone-shaped common cloacal apertures are irregularly spaced among crowded zooid branchial apertures, showing no apparent arrangement into regular systems ( Figure 6b ). The outer test is sparsely covered with fine sand and the colonies have a sky-blue test (5BG8/2), which is apparent on the rims on the branchial apertures. Internally, the test is transparent and gelatinous, containing few sand grains.

Large zooids are crowded in the test. The thorax is 4 mm long and has a short branchial aperture with 6 low, well-defined lobes. The atrial aperture is small, muscular and separate from the long atrial languet ( Figure 7a ). Thirteen longitudinal muscles run on each side from the branchial aperture to the dorsal side of the body wall. The branchial sac has 17–19 rows of 16–18 stigmata per half-row. Ten papillae were counted on each transverse vessel ( Figure 7b ). The abdomen is short (2 mm long),and the gut is twisted to the left forming a horizontal loop posterior to the throax. A bilobate anus opens in the peribranchial cavity adjacent to the sixth row of stigmata. A relatively long pyriform post-abdomen (6 mm long) contains up to 25 testis follicles posterior to several developing ova ( Figure 7c ). No larvae were present in colonies examined in this study.

Remarks

The colony and zooid morphology of specimens collected from Bluff agree closely with the type species from Foveaux Strait described by Brewin (1958a). The in-situ image of the colony ( Figure 6B ) shows large, scattered common cloacal apertures with raised rims, which collapse on removal from water and are not evident in preserved specimens. The zooids of Polyclinum novaezelandiae are distinguished from 3 other species of Polyclinum endemic to New Zealand – P. sluiteri Brewin, 1956 , P. michaelseni Brewin, 1956 and P. cerebrale Michaelsen, 1924 – by a greater number of rows of stigmata in the branchial sac. Furthermore, the colonies of the former 2 species are stalked, while those of P. cerebrale are cushion-shaped with a network of conspicuous sinuous ridges ( Millar 1982), unlike the morphology of P. novaezelandiae specimens collected from Bluff.

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).

Figure 7. Polyclinum novaezelandiae (NIWA68097): (a) abdomen and thorax; (b) a section of the branchial sac showing papillae on transverse vessels and hooked dorsal languets on the dorsal midline; (c) post-abdomen. Scale bars: a = 5.0 mm; b, c = 1.0 mm.