Antarctothoa buskiana ( Hutton, 1873 )

Gordon, Dennis P., 2020, New Hippothoidae (Bryozoa) from Australasia, Zootaxa 4750 (4), pp. 451-476 : 471-472

Antarctothoa buskiana ( Hutton, 1873)

( Fig. 11 A–C)

Diachoris buskiana Hutton, 1873: 94 ; Hutton 1880: 188; Jelly 1889: 228.

Schizoporella hyalina: Hutton 1891: 106 ; Hutton 1904: 297. Non Cellepora hyalina Linnaeus, 1767 .

Celleporella buskiana: Gordon et al. 2009: 291 .

Material examined. OM A88.104 (lectotype) ; NMNZ Pz. 4 (syntype) . NIWA 98922 , 35.8270° S, 174.5224° E, 0 m, coll. D.P. Gordon ; NIWA 127918 , Stn Z9714, 34.3910° S, 172.9690° E 45 m.

Remarks. This little-known epialgal species is notable for its disjunct zooids ( Fig. 11A ), reflected in the original attribution to the unrelated genus Diachoris [i.e. Beania ]. In this regard it superficially resembles Antarctothoa discreta ( Busk, 1854) from the Falkland Islands, but the latter species has distinctive annular transverse ridges. Disjunction in A. buskiana autozooids occurs from the inception of the colony. The ancestrula has a pair of large distolateral pore-chambers that bud the first daughter zooids. These do not touch but, while they are forming, produce a median zooid between them that is not in contact with the ancestrula ( Fig. 11C ). The three daughter zooids are disjunct and connected by tubes.

Almost all zooids are relatively long and tapering, especially the female zooids (cystids), which have the profile of an ice-cream cone. Male zooids are narrower still. Where transverse clusters of female zooids occur together in the colony, disjunctions between them, and between adjacent other zooids, are much less apparent. The autozooidal sinus is evenly U-shaped (i.e. parallel-sided), as is the tiny sinus in the dimorphic combined maternal aperture; the sinus of the male orifice, on the other hand, is proportionally long and narrow ( Fig. 11B ).

Brown (1952) noted that, in 1874, Hutton sent a collection of New Zealand bryozoans to the then British Museum. Among them was a specimen of Diachoris buskiana , which was subsequently registered as 1875.1.5.78.

Antarctothoa buskiana is commonly distributed on thin-bladed brown-algal laminae along the northeast coast of North Island from Coromandel Peninsula to the Spirits Bay region from the low intertidal to 45 m depth.

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.