Mycale (Mycale) cartwrighti Goodwin & Brickle 2012, sp. nov

Mycale (Mycale) cartwrighti sp. nov. (Figure 18) Type material: Holotype: Sample in 95% ethanol, tissue section and spicule preparation on slides. BELUM Mc 7590. Prion Island Site 2, South Georgia (54°001.862’S, 37° 15.032’W); depth 18m; collected by C. Goodwin, D. Poncet, and P. Brewin, 19 th November 2010. Paratypes: Sample in 95% ethanol, tissue section and spicule preparation on slides. BELUM Mc 7638. Bird Sound Site 2, South Georgia (54°01.149’S, 38° 01.026’W); depth 18m; collected by C. Goodwin, S. Cartwright and P. Brickle, 22 nd November 2010. Etymology: Named after Steve Cartwright, member of the expedition dive team. External morphology: In situ appearance: Thickly encrusting lemon yellow sponge (up to 10mm thick) in large patches (> 15cm) with sparsely scattered large oscules. Sub-ectosomal spaces clearly visible through ectosome giving the sponge surface a slightly lumpy appearance (Fig. 18a). Preserved appearance: Very pale yellow crust. Choanosome firm but compressible, ectosome visible as a separate, harder layer. Skeleton: The choanosomal skeleton is formed of thick (up to 20 spicules wide) ascending columns of mycalostyles which anastomise and coalesce. The ascending columns are joined by shorter, thinner columns (1–3 spicules in width). The ectosomal skeleton is formed by the choanosomal columns fanning out at the surface to form a confused tangential ectosomal layer of mycalostyles. Chelae and trichodragmata present throughout skeleton, chelae do not form rosettes (Fig. 18b). Spicules: Measurements from Mc7590. Styles: 349 (407)451 by 9.3 (12.6)16.9µ m. Mycalostyles with a neat rounded head and abruptly taped tip (Fig. 18c). Chelae: 23(35)47µm—rarely 70µ m in Mc7638. Typical mycalid anisochelae with the lower front alae coming to a blunt point (Fig. 18d). Microxea: 12 (23)40µm, very small microxea Remarks: This species can be distinguished from the majority of other Mycale (Mycale) species by the possession of small microxea/trichodragmata which is unusual in the genus Mycale (Table 9). Of those species which do possess these Mycale (Mycale) macrochela Burton, 1932 has sigmas and smaller chelae (7–35µm), Mycale (Aegogropila) meridionalis Lévi, 1963 has trichodragmata 16–17µm but also has sigmas and smaller mycalostyles, Mycale (Aegogropila) nodulosa Goodwin et al., 2011a has similar sized spicules but possesses sigmas, a second minute (5µm) category of microxea and has a clearly reticulate ectosomal skeleton which assigns it to a different subgenus, and Mycale (Carmia) diminuta Sará, 1978 has similarly sized mycalostyles but larger trichodragmata (45–60µm). Mycale (Mycale) brownorum sp. nov. can be distinguished as it also lacks microxea microscleres.