Stryphnus spelunca Kelly & Sim-Smith, 2012, sp. nov.

Stryphnus spelunca sp. nov.

(Fig. 2 E, 7F–K, 8)

Material examined. Holotype ― NIWA 52582: Port Abercrombie, Great Barrier Island, 36.141º S, 175.307º E, RV Kaharoa, 5 m, 26 Apr 1999, additional vouchers of the holotype are in the CRRF reference collection (0 CDN 6808- K) and at the USNM (USNM 1182997). Paratype ― NIWA 73802: NIWA Stn TAN1105/133, North Taranaki Bight, 38.415° S, 173.341° E, 217–218 m, 4 Apr 2011.

Type locality. Port Abercrombie, Great Barrier Island.

Distribution. Known only from the type locality.

Description. Thick encrusting sponge attached to rock substrate, 150 mm wide and 10–25 mm thick (Fig. 2 E). Clumps of tiny oscules are scattered over the surface of the live sponge, oscules are invisible on the preserved specimen. Ectosome 1–2 mm thick and easily detached from the sponge. Surface smooth, undulating, harsh to the touch. Texture firm, just compressible. Colour in life is dark brownish black throughout, colour in ethanol is dark brown.

Skeleton. Ectosome is 1000–1300 µm deep and is clearly differentiated from the underlying choanosome, which is very densely pigmented in comparison. The ectosome appears to be moderately permeated with fibrillar collagen, which becomes more heavily pigmented towards the lower boundary. Large, well-defined aquiferous channels permeate both the ectosome and choanosome. Sanidasters and amphisanidasters form a very dense crust approximately 60 µm deep at the surface, and these microscleres are also scattered throughout the ectosome, and to a lesser extent, the choanosome. Plagiotrianes are mainly confined to ectosome, where they are very abundant and lie in all directions. Oxeas form occasional short tracts in the choanosome, but most are scattered with no particular orientation. These megascleres occasionally protrude from the sponge surface. Oxyasters are confined to the choanosome and are moderately densely scattered throughout the choanosome.

Spicules. Megascleres (Fig. 7 F–G) are oxeas (Fig. 7 F), medium length, stout, usually slightly curved, fusiform with sharply pointed ends, 1497 (1135–1750) x 35 (23–41) μm; plagiotriaenes (Fig. 7 G) resembling calthrops, highly variable in size with a conical rhabdome, 256 (94–387) μm that is only slightly longer than clads, 201 (110– 294) μm. The clads point forward at a 45° angle and have sharply pointed tips. Cladome width 334 (194–530) μm.

Microscleres (Fig. 7 H–K) are oxyasters (Fig. 7 H) with 3–7 very fine acanthose rays, 33 (19–49) μm wide; amphisanidasters ( Fig. 7 I) with short, conical rays clustered at either end of the shaft or along the shaft, rays sparsely acanthose and spined, 10 (8–12) μm long; sanidasters (Fig. 7 J, K) with a straight axis and numerous short, blunt spines that are irregularly spaced along the length of the axis, the entire spicule is sparsely to moderately acanthose, 13 (11–16) μm long.

Substrate, depth range, and ecology. Holotype growing on the wall of a cave 20 m in from the cave opening, at 5 m depth; paratype much deeper in rock and boulder field at about 218 m.

Etymology. Named for the cave habitat of this species (spelunca = cave in Latin).

Remarks. Stryphnus spelunca sp. nov. is very similar to S. novaezealandiae sp. nov. in morphology; both are thickly encrusting with a harsh texture. The two species also have a similar ectosomal and choanosomal architecture, with plagiotriaenes packed in the ectosome. Perhaps the greatest point of similarity between the two species is the possession of plagiotriaenes that look like calthrops, and the brownish black colouration in life, characters not present in other New Zealand species of Stryphnus.

Given the similarities of the two species and the fact that only two specimens of S. spelunca sp. nov. was found in quite disparate locations, one might reasonably consider S. spelunca sp. nov. to be conspecific with S. novaezealandiae sp. nov. However, the oxeas and plagiotriaenes are consistently shorter in S. spelunca sp. nov. than in S. novaezealandiae sp. nov. (oxeas 600 μm, plagiotriaene rhabdome 136 μm, cladome width 82 μm), and sanidasters and oxyasters are shorter in S. spelunca sp. nov. by some 10–15 μm. Furthermore, amphisanidasters are absent in S. novaezealandiae sp. nov. The ectosome of S. spelunca sp. nov. is also notably thinner than that of S. novaezealandiae sp. nov. These megasclere and microsclere differences are considered sufficient to distinguish S. spelunca sp. nov. from S. novaezealandiae sp. nov. at this time.