Dysidea tuapokere Mc Cormack & Kelly & Battershill 2020, sp. nov.

Dysidea tuapokere sp. nov.

Figs 1–4

urn:lsid:zoobank.org:act: F79D832D-AD90-44CE-A18C-83DB4E29306C

Material examined. Pilot Bay, Tauranga Harbour, Bay of Plenty: Holotype— NIWA 92974, 37.380° S, 176.102° E, 5–12 m, 27 Sep 2017. Paratypes— NIWA 113646–113649, 37.380° S, 176.102° E, 13 m, 05 Feb 2019.

Type location & distribution. Pilot Bay, Tauranga Harbour, Bay of Plenty, New Zealand, 12–13 m.

Description. Sponge forms a cavernous mass of interconnected lobate digits, sprawling across the substrate, up to 4–23 cm long, 14–15 cm wide, 2–4 cm high, in general dimensions, digits about 1–3 cm thick (Fig. 2A). Surface conulose in life, conules predominantly clustered on the tips of the lobes (Fig. 2B), but scattered irregularly on the surface, about 0.5–1.0 mm high; conule apices resemble hairs in the preserved specimen (Fig. 2C). Dermal membrane thin and translucent in life and after preservation. Cobwebs of fibrillar collagen in the surface membrane are visible, stretching between the tips of primary fibres, between which are set membranous oscules, about 2 mm diameter (Fig. 2A, B). Conules accentuated in the shrunken, preserved condition (Fig. 2C). Texture soft, compressible, slightly elastic and fragile due to the incorporation of large amounts of detritus in the fibres. Colour in life, translucent lilac under natural lighting in situ (Fig. 2A, C), and tan in shaded sections (Fig. 2C). Cream to tan in preservative.

Skeleton. Primary fibres heavily cored with sand and foreign spicule fragments, about 308 (200–500) µm thick (Fig. 3A), frequently bifurcating or divaricating further below the surface (Fig. 3B). Secondary fibres are variable in thickness, often flanged where they join the primary fibre, and generally only partially cored, in which case the laminated golden spongin is visible surrounding the inclusions in histological sections (Fig. 4A, B); 69 (50–100) µm thick. The secondary fibres are supported by cored auxiliary fibres that link the secondary and primary fibres; 10–15 µm thick (Fig. 3B).

The overall architecture is extremely irregular and mesh size difficult to provide meaningful dimensions for but range from about 0.5–3 mm wide. The irregularity of the overall skeleton is evident in Figs 2A and B which show the surface conules clustered in groups on the tips of the branches, being evidence of extensive divarication below the surface [compare to the regularity of the surface in D. cf. cristagalli (Fig. 5) and D. teawanui sp. nov. (Fig. 6D)].

The ectosome consists of a dense band of pigmented collagen fibrils (Fig. 4C) and appears cavernous in sections; about 30–100 µm deep, strands of which stretch between the apex of the primary fibres. A translucent dermal membrane is raised by large primary fibres, rarely with any inclusions of detritus; unarmoured (Fig. 4C). The choanocyte chambers are eurypylous, 30–50 µm diameter, and clearly visible in the choanosome (see Fig. 3A, 4A, B). Detritus is scattered lightly through the choanosome and ectosome.

Substrate, depth range and ecology. Found predominantly on rocky reefs within a relatively sheltered location. Associated with kelp forests or sponge gardens. Depth range is 5– 12 m.

Etymology. Named for the beautiful, translucent, pale lilac colouration of this species in life (tuapokere, violet; te reo Māori). This species name was accepted and approved by local Tauranga Moana iwi, Ngāti Ranginui, Ngāi Te Rangi and Ngāti Pūkenga.

Remarks. Dysidea tuapokere sp. nov. is a shallow-water harbour species, with a cavernous lobo-digitate morphology, similar to several species described or noted from New Zealand waters. Most of these species are, however, inadequately described and figured, so only a limited comparison can be made in most cases. The most recently described species, D. cristagalli Bergquist, 1961a, was collected from the intertidal zone on Rangitoto Island in the North Island’s Waitemata Harbour, and the Noises Islands in the inner Hauraki Gulf (Table 1). Dysidea cristagalli differs morphologically from D. tuapokere sp. nov. in being, “erect, tubular in shape, with several tubes coalescing to give a tubula-flabellate condition” (Bergquist 1961a: Fig. 1b). The oscules were “apical, giving access to deep cloacae”, a completely different morphology to the cavernous lobo-digitate form of D. tuapokere sp. nov. which has small, flush oscules scattered across the sponge. Additional key differences are the colouration in life (D. cristagalli: “ash-grey”; D. tuapokere sp. nov.: translucent lilac) and skeletal architecture: Bergquist (1961a) stated that she could not distinguish between the primary and secondary fibres, which ranged in diameter from 20–200 µm, whereas in D. tuapokere sp. nov. the secondary fibres are much smaller than the primaries which can be up to 500 µm thick. Bergquist (1961a) also noted that the fibres of D. cristagalli are exclusively packed with broken sponge spicules.

Several specimens have been attributed to D. cristagalli with hesitation, including one by Kelly in McNamara et al. (2005). That sponge (NIWA 101432) was described as forming a “spherical mass of meandering ridges and interconnected short blunt branches”, with oscules situated on the ends of branches and along the tops of ridges (Fig. 5). While this arrangement is superficially similar to the “tubula-flabellate” condition of Bergquist’s D. cristagalli, the oscules in NIWA 101432 do not lead to deep cloacae (Fig. 5). Although the colour of NIWA 101432 was cited as “greyish white”, the in -situ image was taken in natural lighting and is misleading with red light absorption at depth. The skeleton of NIWA 101432 is comprised of a loose reticulation of large sand-grains cemented into fibres with spongin clearly visible, connected to each other by numerous fibres containing predominantly spicule debris, features not noted by Bergquist (1961a). With the benefit of hindsight, the sponge NIWA 101432 is almost certainly not Dysidea cristagalli, most likely representing a new species. Dysidea tuapokere sp. nov. is distinct from NIWA 101432 in the sandy surface texture of the latter (implying a dermal membrane charged with detritus), and in the extremely regular disposition of the surface conules, compared to that in D. tuapokere sp. nov. (compare Fig. 2A, B).

Dysidea spiculivora (Dendy, 1924) was described as “irregularly massive, sub-digitate, 54 mm long, 20 mm diameter, probably repent,” with a “coarsely sub-conulose surface with conuli low and far apart”. The interior was cavernous and no oscules were seen. The colour in life was described as “white, with a curiously translucent appearance”. Dendy described the skeleton as an irregular jumble of spicules and a dermal skeleton was not noted by Dendy (Table 1). Two specimens closely comparable to this, NIWA 52374 and NIWA 52390, have been collected since this first description: the defining characteristics are the translucent white colouration in life, the cavernous interior and broadly sub-conulose surface.

Dysidea sp. ‘a’ Brøndsted, 1924, from the Auckland Islands (Table 1), is closely comparable to D. tuapokere sp. nov. in morphology, composed of “densely anastomosing, evenly thick branches” about 40–50 mm long, with a regular, abundantly conulose surface and small oscules, a “thin, pellucid dermal membrane”, a soft consistency and the colour of flesh. However, no skeletal description was attempted as Brøndsted admitted to unfamiliarity with the genus; a direct comparison is not possible in this work. The likelihood of conspecificity of D. tuapokere sp. nov. with this ill-defined, almost unrecognisable Auckland Island specimen, is low: there are only a few precedents of well-characterised, deep subtidal species, existing off both the North Island and Subantarctic New Zealand (see Sim-Smith & Kelly 2019).