Clathria (Microciona) matthewsi Goodwin & Brickle 2012, sp. nov.

Clathria (Microciona) matthewsi sp. nov.

(Figure 8)

Type material: Holotype: BELUM Mc 7606. Sample in 95% ethanol, tissue section and spicule preparation on slides; Rosita Harbour Site 2, South Georgia (54°00.649’S, 37° 25.618’W); depth 11.5m; collected by C. Goodwin, J. Brown, and S. Brown, 20 th November 2010.

Paratypes: Samples in 95% ethanol, tissue section and spicule preparation on slides. BELUM Mc 7625. Right Whale Bay, South Georgia (54°00.173’S, 37° 40.856’W); depth 18m; collected by C. Goodwin, J. Brown and S. Brown, 21 st November 2010. BELUM Mc 7631 and BELUM Mc 7632. Bird Sound Site 1, South Georgia (54°02.058’S, 38° 00.242’W); depth 18m; collected by C. Goodwin, S. Cartwright and P. Brickle, 22 nd November 2010. BELUM Mc 7667. Husvik, South Georgia (54°10.285’S, 36° 40.412’W); depth 18m; collected by C. Goodwin, D. Poncet and P. Brewin, 26 th November 2010. BELUM Mc 7678. Green Island, Stromness, Site 1, South Georgia (54°09.448’S, 36° 39.752’W); depth 17.4m; collected by C. Goodwin, P. Brickle and S. Cartwright, 27 th November 2010.

Etymology: Named for marine mammal biologist Dr Leonard Harrison Matthews who worked on South Georgia during the Discovery Antarctic Investigations.

External morphology: In situ appearance: Lemon to custard yellow thinly encrusting (<3mm thick) sponge forming small patches, up to 15cm maximum diameter, on bedrock. The surface of the sponge is smooth without obvious exhalent canals or oscules (Fig. 8a).

Preserved appearance: Thin cream crust with a smooth surface.

Skeleton: The choanosome is plumose with ascending choanosomal columns of primary acanthostyles very strongly echinated by secondary acanthostyles. Columns placed closely so that the ends of the echinating acanthostyles intermesh. The ectosomal skeleton consists of brushes of a separate category of ectosomal styles (Fig. 8b).

Spicules: Measurements from Mc7606.

Primary acanthostyles: 244(354)432 by 15.8(18.3)24.5µm. Head not tylote. Spined only basally, to about 1/8 up shaft from the head, with small spines (Fig. 8c).

Secondary acanthostyles: 85(108)196 by 9.3(13.8)20.8µm. Entirely spined with large conical spines along their entire length, head not tylote (Fig. 8d).

Ectosomal styles: 168(217)254 by 7.6(9.2)11.5µm. Microspined on head (Fig. 8e).

Toxa: 59(86)121µm with spined ends (Fig. 8f).

Chelae: 9(10)11µm very abundant (Fig. 8g).

Remarks: We have assigned these specimens to the subgenus Clathria (Microciona) on the basis of their encrusting growth form and plumose skeletal architecture (Hooper 2002). There are four species of Clathria (Microciona) which have been recorded from the Antarctic and South Atlantic: C.antarctica (Topsent, 1917), C. basispinosa (Burton, 1934), C. tuberculata (Burton, 1934), and C. sigmoidea (Cuartas, 1992). However, none of these possess chelae and therefore can be readily distinguished from our specimens.