Hippothoa pacifica Gordon, 1984

Gordon, Dennis P., 2020, New Hippothoidae (Bryozoa) from Australasia, Zootaxa 4750 (4), pp. 451-476 : 468-469

Hippothoa pacifica Gordon, 1984

( Fig. 10A, D )

Hippothoa divaricata pacifica Gordon, 1984: 111 , text-fig. 10C, F, pl. 43A, B; Gordon et al. 2009: 291.

Material examined. Holotype: NIWA 1279 (H-282), 30.5533° S, 178.5267° W, 125 m. Paratype: NIWA 1280 (P-567), same data as holotype . Other material: NIWA 73295 , 34.2685° S, 173.0248° E, 168 m ; NIWA 98914 , 46.7250° S, 165.7750° E, 286 m ; NIWA 144794 , 33.9875° S, 171.7508° E, 170–174 m ; NIWA 26694 , 26696 , 98202 , 98214 , 98215 , 42.8292° S, 177.4218° W, 826 m.

Remarks. Gordon & Ryland (1977) noted the close similarity between European and New Zealand specimens of Hippothoa divaricata , treating them as conspecific. Differences appeared trivial, including “the autozooidal sinus, which is more U-shaped, and the pore-chambers which are more triangular” in the New Zealand form. Gordon (1984) described the latter as a new subspecies, H. divaricata pacifica , further noting more-elongate zooeciules, fewer pore-chambers and a kenozooidal ancestrula, but was not able to illustrate the ovicell in the type specimens, noting, however (in remarks on Hippothoa calciophilia Gordon, 1984, p. 110 ), that the apex of the ovicell in H. divaricata pacifica was bimucronate.

The new material gives information on the ovicell, of which the ooecium is indeed bimucronate ( Fig. 10A ), appearing as a pair of converging, rimmed, drop-shaped tubular (elevated) pseudopores in non-eroded specimens. De Blauwe (2009) has illustrated by SEM Belgian material of H. divaricata —the sole ovicell shown has an ooecium with more-widely separated elevations, each with a small excavation in it. The specimen additionally shows that the autozooids are proportionally narrower and more-strongly carinate than in the New Zealand form, which is here raised to full species rank. Moyano’s (1986) illustrations of H. divaricata from Chile resemble H. pacifica but the ancestrula has an orifice and operculum.

Hippothoa pacifica ranges throughout New Zealand from the vicinity of Raoul Island to southern South Island (c. 29– 47° S), where it seems to be restricted to calcareous substrata. It occurs from shallow coastal water to 826 m depth.

Figures

FIGURE 10. Four species of Hippothoa: A, D, Hippothoa pacifica Gordon (NIWA 98202), respectively showing an ovicellate zooid in lateral view with a pristine ooecium perforated by two elevated apical pores (the curved part of a rim seen between them), and dimorphic ovicellate orifice (apical pseudoporous mucro eroded) and autozooidal orifice; B, C, E, F, Hippothoa peristomata Gordon, respectively showing a frontal view of two autozooids (NIWA 94240), an ovicellate zooid (NIWA 94240), an autozooid in lateral profile (NIWA 120856) and a kenozooid (NIWA 94240); G, H, Hippothoa flagellum Manzoni (part NHMUK 97.5.1.793), autozooidal orifice and dimorphic female orifice; I, J, Hippothoa watersi Morris (NIWA 144795), autozooidal orifice and dimorphic female orifice. Scalebars: A, E, F, 200 μm; B, 300 μm; C, D, 100 μm; E, F, 200 μm; G–J, 20 μm.