Stryphnus atypicus, Kelly, Michelle & Sim-Smith, Carina, 2012

Stryphnus atypicus sp. nov.

( Fig. 2 View FIGURE 2 C, 6 I –P, 8)

Material examined. Holotype ― NIWA 44225: NIWA Stn W0446- 8, Chatham Rise, 43.245 ° S, 175.444 ° E, 71–76 m, 22 Feb 1995. Paratype ― NIWA 44527: NIWA Stn W0454- 3, Chatham Rise, 43.451 ° S, 175.109 ° E, 126–130 m, 22 Feb 1995.

Type locality. Chatham Rise.

Distribution. Known only from the type locality.

Description. The holotype is a small piece of a sponge that appears to have been thickly encrusting on rock substrate, 40 mm long x 20 mm wide x 30 mm thick ( Fig. 2 View FIGURE 2 C). Ectosome is 1 mm thick, detachable, and clearly visible in the cut surface. No oscules are visible. Texture is firm, slightly compressible, interior is smooth to the touch. Surface is smooth, granular to the touch. Colour in ethanol is medium brown, interior is tan.

Skeleton. Ectosome 1000–1200 µm deep and clearly differentiated from the underlying choanosome by a dense granular layer on the lower boundary. The ectosome is cavernous and is moderately densely permeated with fibrillar collagen, especially towards the lower ectosomal boundary. Heavily pigmented cells are moderately abundantly scattered throughout the ectosome and choanosome. Both the ectosome and the choanosome are riddled with large aquiferous channels. Amphisanidasters form a thin, dispersed crust on the surface of the sponge, and are sparsely scattered in the underlying ectosome and choanosome. Oxyasters are confined to the choanosome where they are sparse. Dichotriaenes are infrequent and are generally found in the ectosome with their cladome at the surface of the sponge, but are also present in the choanosome. Protriaenes and anatriaenes are present, albeit, rarely. Slender oxeas are grouped in untidy bundles in the choanosome that lie obliquely or paratangentially to the surface. Oxeas are generally confined to the choanosome where they form untidy tracts.

Spicules. Megascleres ( Fig. 6 View FIGURE 6 I–L) are oxeas ( Fig. 6 View FIGURE 6 I), small, slender, straight, fusiform with sharply pointed tips, 1054 (833–1340) x 18 (12–23) μm; dichotriaenes ( Fig. 6 View FIGURE 6 J) with short rhabdomes 480 (303–655) μm, and large variation in cladome width, 213 (86–287) μm. Protoclads are short, 49 (27–78) μm, and protrude forward at an angle of approximately 45 °, deuteroclads are usually slightly longer than protoclads, 65 (10–109) μm, and are horizontal with pointed tips; anatriaenes ( Fig. 6 View FIGURE 6 K), very long and slender, often curved, with a tiny grapnel-like head 14 (12–17) μm wide. Complete anatriaenes could not be found as they are very delicate and break easily, but the shaft is approximately 2 μm wide and more than 500 μm wide long; protriaenes ( Fig. 6 View FIGURE 6 L), short and very slender, 425 (380–515) μm long with a cladome width of 24 (18–34) μm (n= 8).

Microscleres ( Fig. 6 View FIGURE 6 M–P) are oxyasters ( Fig. 6 View FIGURE 6 M) with relatively thick, blunt, acanthose rays, 23 (14–33) μm diameter; amphisanidasters ( Fig. 6 View FIGURE 6 N–O) with a short, thick linear ridged axis, sparsely acanthose, 8 (7–11) μm long; sanidasters ( Fig. 6 View FIGURE 6 P), highly irregular, with a long thin linear axis and spines of irregular length and shape, 13 (12–15) μm long. It is possible that these are developing amphisanidasters.

Substrate, depth range, and ecology. Attached to rocky substrate between 71– 130 m.

Etymology. Named for the presence of anatriaenes and protriaenes which are atypical in the genus Stryphnus ( atypicus = Latin for atypical).

Remarks. Stryphnus atypicus sp. nov. has the normal spicule characteristics of the genus; oxeas as the choanosomal megasclere, short-shafted dichotriaenes in the ectosome and choanosome, an ectosomal crust of amphisanidasters and sanidasters, and oxyasters in the choanosome. However, the ectosome of S. atypicus sp. nov. is quite dense compared to other species, and it has rare anatriaenes and protriaenes, a feature unprecedented in any known species of Stryphnus , but common in the closely related genus Ancorina . Uriz (2002) states that the main distinction between Ancorina and Stryphnus is the length of the triaenes; Ancorina has long-shafted triaenes that are generally> 1000 µm, whilst Stryphnus has short-shafted triaenes generally <1000 µm. The short shaft length of the dichotriaenes in S. atypicus sp. nov., and the possession of sanidasters and amphisanidasters, excludes the species from Ancorina , and the fibrous nature of the ectosome excludes it from Ecionemia . We have thus, chosen to emend the definition of the genus Stryphnus to include anatriaenes and protriaenes, albeit rarely.

In addition to the possession of anatriaenes and protriaenes, S. atypicus sp. nov. differs from S. mucronatus ( Schmidt 1868) , S. fortis , S. niger , S. progressus , S. raratriaenus , and S. unguiculus Sollas, 1886 , by the size of its oxeas; the oxeas of S. atypicus sp. nov. are approximately half the size of the above described species. Stryphnus atypicus sp. nov. has similar sized oxeas to S. ponderosus but the sanidasters of S. ponderosus are longer and more regular, with longer thinner spines than those of S. atypicus sp. nov.