Protosuberites novaezelandiae sp. nov.

( Figs 1, 2, 7, 8; Table 4)

Material examined. Calypso hydrothermal vent field ( Southern vent field), southwest of White Island, Bay of Plenty: Holotype — NIWA 32136, University of Kiel Stn SO192-2/3, 37.688° S, 177.123° W, 192 m, collected by TV Grab, 27 April 2007. Paratypes — NIWA 32135, 32140, University of Kiel Stn SO192-2/7, 37.688° S, 177.123° W, 191 m, collected by ROV, 28 April 2007; NIWA 52839, IFM GEOMAR Stn SO135/110, 37.688° S, 177.122° E, 189–192 m, collected by rock dredge, 11 Oct 1998.

Other material. NIWA 52838, IFM GEOMAR Stn SO135/103, 37.695° S, 177.101° E, 179–181 m, collected by rock dredge, 10 Oct 1998; NIWA 52851, IFM GEOMAR Stn SO135/110, 37.688° S, 177.122° E, 189–192 m, collected by rock dredge, 11 Oct 1998.

Type location & distribution. Calypso hydrothermal vent field, Bay of Plenty, New Zealand, 179–192 m.

Description. Thickly encrusting on hard rocky substrate, appearing ‘stretched’ in places, about 5–10 mm thick, growing in patches of about 50–100 mm wide. Encrustations may give rise to low mounds, lobes, flabby expanses and finger-shaped projection, 5–10 mm diameter ( Fig. 7A, B). Oscules are not obvious in life but appear to be at the ends of some fingers in in situ images. The surface is macroscopically smooth to undulating in life, with a stretched, slightly micro-knobbed appearance when out of water ( Fig. 7C). Sediment catches in places where ectosomal spicules protrude beyond the surface rendering the texture slightly fuzzy ( Fig. 7D). Texture in life slightly compressible, rubbery, corky, flexible. Colour in preservative ranges from light to dark cream yellow, to peach-coloured, to deep dull pink (NIWA 52838).

Skeleton. Choanosome composed of wavy tracts of large tylostyles aligned longitudinally through the axes of flabellate and finger-like portions of specimens ( Fig. 7E), diverging towards the surface in encrusting portions ( Fig. 7F, G). Tracts range from about 100–1100 µm wide and are interspersed with numerous free tylostyles. About 1000 to 1500 µm below the surface, tracts branch and diverge towards the surface, terminating below well separated surface bouquets of smaller tylostyles, the sharp tips of which project cleanly from the surface by about 60–150 µm.

Spicules. Megascleres ( Table 4; Fig. 8) are tylostyles with well-developed, spherical heads with a slight protrusion at the tip, ranging in length from about 150–920 µm long and 7–25 µm thick, slightly sinuous and unevenly thickened along the straight shaft, thicker in the upper half. Examination of histological sections of the ectosome and choanosome reveal at least two clear size categories of tylostyles, the smaller in the ectosomal brushes (170–350 µm long), the largest in the deep choanosomal tracts (500–920 µm long).

Substrate, depth range and ecology. Attached to volcaniclastic rock covered in sediment and associated with high densities of other sponges and an undescribed orange anemone, 179– 192 m.

Etymology. Named for the first record of the genus in the New Zealand region.

Remarks. In the Pacific Ocean region, two species were described from the Southern California Bight [ P. mexicensis (de Laubenfels, 1935), P. sisyrnus (de Laubenfels, 1930)], Australia [ P. epiphytum ( Lamarck, 1815); P. proteus ( Hentschel, 1909), and Chile [ P. epiphytoides ( Thiele, 1905)]. The most common species in this region, stretching from the Indian Ocean to Palau in the Central Pacific, is P. diversicolor Becking & Lim (as Suberites), often found in land-locked marine lakes ( Kelly & Bell 2015).

In terms of spicule dimensions, the closest species to P. novaezelandiae sp. nov. are P. mexicensis from the South Californian Bight, with tylostyles up to 1000 µm long ( Table 5), and P. proteus from Shark Bay, southwestern Australia, with tylostyles ranging from 15 8–808 µm long ( Table 5). The Californian species has much larger megascleres than P. novaezelandiae sp. nov., and according to de Laubenfels (1935), the sponge is a thin encrustation on a large spicule of hexactinellid origin. The choanosome has a confused arrangement with bouquets at the surface, but there is no appreciable difference between the lengths of the tylostyles in the ectosome and choanosome. Protosuberites proteus from tropical Shark Bay in Western Australia, has very similar spiculation to P. novaezelandiae sp. nov., but is a shallow water sponge collected from estuaries and rocky reefs between 3 and 12 m deep. The sponge is much thicker (up to 6 cm thick) than the New Zealand species ( 5–10 mm thick) which is found in much deep waters ( 179–192 m). The two species are separated primarily on their disjunct geographic distributions (shallow tropical estuarine Western Australia vs deep-water hydrothermal vent field in temperate eastern New Zealand).

Most authors do not differentiate ectosomal and choanosomal categories of megascleres in species of Protosuberites from the South Pacific and Southern Ocean region ( Table 5). However, in those species with

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choanosomal tracts that diverge below the ectosome, such as in P. hendricksi ( Table 5) and in P. novaezelandiae sp. nov., there is a striking difference in the lengths of spicules in these species (e.g. Fig. 5F; Table 4), and some evidence that, as in many Suberitidae genera, a subectosomal category may also be discernible, but difficult to measure (see Samaai & Gibbons 2005).

Protosuberites is well represented in the Atlantic Ocean and further north (13 species): North and Celtic Seas [ P. incrustans (Hansen) and sensu (Stephens); P. denhartogi Van Soest & de Kluijver; P. durus (Stephens)]; Western Mediterranean and Black Seas [ P. brevispinus (de Laubenfels); P. ectyoninus (Topsent); P. mereui Manconi; P. modestus (Pulitzer-Finali); P. prototipus; P. rugosus (Topsent)]; North Atlantic [ P. capillitium (Topsent); P. ferrerhernandezi (Boury-Enault & Lopes)]; Western Tropical Atlantic [ P. geracei (Van Soest & Sass)], and across the Western Indian Ocean [ P. reptans (Kirkpatrick) and P. hendricksi Samaai & Gibbons from South Africa; P. longispiculus (Burton) from the Maldives] and Southeast Asia, where the earliest species were described from the brackish, land-locked Chilka Lake of eastern India [ P. aquaedulcioris (Annandale); P. lacustris (Annandale)] and P. collaris Annandale from Krakatau, Indonesia. A sixth species has been described from Cheju Island, Korea, P. nestus (Sim & Kim). A review of all species and their skeletal architecture and spicule dimensions would be very useful but is beyond the scope of this work.