Hippothoa watersi Morris, 1980

Gordon, Dennis P., 2020, New Hippothoidae (Bryozoa) from Australasia, Zootaxa 4750 (4), pp. 451-476 : 469-471

Hippothoa watersi Morris, 1980

( Fig. 10I, J )

Hippothoa flagellum: Gordon & Ryland 1977: 22 (part), fig. 3H; Gordon 1984: 111, text-fig. 10E, pl. 43E–G; Moyano 1986: 102, pl. 2; Gordon 1989: 25, pl. 11E–G; Gordon et al. 2009: 291. Non Hippothoa flagellum Manzoni, 1870 .

Material examined. NIWA 3795 , Stn KAH0204/09, 34.1113° S, 174.1382° E, 562–600 m ; NIWA 3797 , Stn KAH0204/27, 34.1202° S, 174.0940° E, 540–554 m ; NIWA 23400 , 49.6132° S, 178.7777° E, 287–350 m ; NIWA 92725 , Stn W511, 43.2417° S, 175.4583° E, 84–88 m ; NIWA 127732 , Stn Z18000, 46.9400° S, 168.1550° E, 42 m ; NIWA 144795 , Stn Z9677, 34.3690° S, 172.8250° E, 55 m ; NIWA 144801 , Chatham Islands 1954 Expedition Stn 24, 43.6033° S, 176.8083° W, 69 m ; NIWA 144804 , Cape Turnagain , 40.4933° S, 176.6100° S, 0.5 m . Also H. flagellum (part NHMUK 97.5 .1.793, Falmouth) .

Remarks. Hippothoa flagellum , first described from the Italian Pliocene, has been accorded a virtually global Recent distribution, ranging from Norway to West Africa ( Hayward & Ryland 1999) and the South Atlantic ( Morris 1980), the southeastern United States and Caribbean, the Pacific Ocean from Japan, Hawaii, California and Mexico ( Morris 1980), New Zealand ( Gordon 1984, 1989), Chile ( Moyano 1986) and Antarctica (Hayward 1985). Morris (1980), however, distinguished New Zealand and Australian material as a separate species, particularly highlighting the narrower, almost ‘triangular’ shape of the autozooidal orifice ( Fig. 10I ). SEM images show that, immediately proximal of the sinus, there is a slight channel between two slight elevations. The female orifice is weakly sinuous, with a median concavity flanked by a pair of slight transverse elevations ( Fig. 10J ).

SEM comparison of New Zealand specimens with a colony of H. flagellum from Falmouth, England shows consistent differences that justify Morris’ decision—not only is the autozooidal orifice in H. flagellum less tapered ( Fig. 10G ), the proximal orificial rim of the female zooid ( Fig. 10H ) lacks the slight eminences that confer the appearance of sinuosity. Further, almost all characters in H. watersi are smaller on average than in H. flagellum , with non-overlapping metrics (one exception being the width of the female zooid).

Morris (1980) was almost certainly correct in splitting H. flagellum [we await confirmation from gene sequencing], whereas later authors have vacillated. For example, Gordon (1984, 1989) thought that H. watersi could be included in H. flagellum ; and Hippothoa belgica Hayward & Thorpe, 1989 was correctly segregated by these authors from nominal look-alike Hippothoa distans MacGillivray, 1869 , but later subsumed in the synonymy of H. flagellum ( Hayward 1995) . [ Hastings (1979) and Gordon (1984) had clarified the status of H. distans , which has two pairs of lateral pore-chambers and a pseudoporous ooecium.] The reason for the reluctance to split H. flagellum is the number of shared characters; not only do H. flagellum , H. watersi and H. belgica look very similar, they all have only a single pair of lateral pore-chambers, and both H. flagellum and H. watersi have similar zooeciules and a kenozooidal ancestrula. Differences are most obvious in orificial characters.

Morris (1980) included Challenger material from Heard Island (South Indian Ocean) in H. watersi , but her illustrations give evidence that it is either H. belgica or yet another new species. She also included Pliocene New Zealand material in her synonymy, but noted differences in orifice shape compared to the Recent holotype specimen.

Hippothoa watersi ranges throughout the New Zealand region from the Kermadec Ridge to the western approaches to Foveaux Strait at 0.5–635 m depth. Morris (1980) also reported it from Port Phillip Heads, Victoria, Australia. It is clear from the illustrations in Moyano (1986) that a colony from Madre de Dios Archipelago, southern Chile, also belongs to this species.

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.