Antarctothoa cancer ( Hutton, 1873 )

Gordon, Dennis P., 2020, New Hippothoidae (Bryozoa) from Australasia, Zootaxa 4750 (4), pp. 451-476 : 472-473

Antarctothoa cancer ( Hutton, 1873)

( Figs 11 D–G; 12)

Lepralia cancer Hutton, 1873: 97 ; Hutton 1880: 192; Jelly 1889: 228.

Schizoporella hyalina var. cornuta: Hutton 1891: 106 . Non Schizoporella hyalina var. cornuta Busk, 1854 .

Hippothoa cornuta var. holostoma Levinsen, 1909: 278 , pl. 21, fig. 8.

Celleporella cancer: Gordon et al. 2009: 291 .

Material examined. NIWA 144802 , 37.4008° S, 174.7065° E, Port Waikato, 0 m on Vidalia colensoi (Hook.f & Harv.) J.Agardh ; NIWA 144816 , 40.4921° S, 176.6095° E, Cape Turnagain beach drift on Pterocladiella capillacea (S.G.Gmel.) Santel. & Hommers ; NIWA 144826 , 144836 , 40.6199° S, 176.4151° E, Akitio beach drift on P. capillacea .

Remarks. This distinctive endemic hippothoid is easily recognised by its rounded distally projecting hollow suboral umbo, which is flanked by a similar projection either side of the orifice ( Figs 11D, F ; 12 ). This arrangement, i.e. an orifice flanked by three prominent umbones—is also seen in the ancestrula, except that the lateral pair of umbones is produced not by the ancestrula, but by the first pair of daughter zooids ( Fig. 11E ). As in A. buskiana , the ancestrula has a pair of large distolateral pore-chambers that bud the first daughter zooids. These do not touch; however a small proximal part of the median zooid that is budded between them just touches the ancestrular rim.

Zooids are almost parallel-sided but tend to narrow a little towards the generally truncate proximal margin. Female zooids (cystids) are typically shorter and wider than autozooids, with ooecia that are wider still. Dimorphic combined maternal apertures lack flanking umbones and have a tiny, variable sinus that rages from a broad V to a small U (a mere nick) in shape.

A specimen of this species was sent by Hutton to the Natural History Museum in London; it is still registered as syntype 1875.1.5.22.

Antarctothoa cancer seems to be restricted to the North Island, including the Auckland–Northland area, on both east and west coasts, where it forms tiny encrustations on narrow-bladed red algae, especially Vidalia colensoi , and also along the southeastern coast on Pterocladiella capillacea .

Figures

FIGURE 11. Antarctothoa buskiana (Hutton) (NIWA 98922): A, disjunct ovicellate zooids and autozooids; B, male, female and autozooidal orifices; C, early astogeny. Antarctothoa cancer (Hutton) (NIWA 144802): D, ovicellate and non-ovicellate zooids; E, ancestrula and adjacent zooids; F, lateral profile of autozooidal orificial region; G, dimorphic female orifice showing proximal nick. Scalebars: A, D, 300 μm; B, F, 100 μm; C, E, G, 200 μm.

FIGURE 12. Antarctothoa cancer (Hutton) (NIWA 144802). En face view of autozooidal, female and male operculate orifices. Scalebar: 300 μm.