Clathria (Microciona) antarctica

Clathria (Microciona) antarctica (Topsent, 1917)

Figure 5

Material examined. Two specimens (MSNG N° 59507, MACN IN-41005) were found at station 4, at 54° 44.02’S and 62° 12.98’ W; 804 m (labeled during the cruise as NBP 05/08 TB 4 #31). Collection date: April 2008. Collector: Laura Schejter.

Description. Our specimens are massive, light brown to slightly grey, 64 x 23 x 24 mm (Figure 5 A). Spicules are 2 categories of styles (sometimes subtylostyles), occasionally basally-spined, 350–(415±45)–487 x 7.5 µm and 515–(603±50)–780 x 12.5–(17±3)–20 µm (Figure 5 B); acanthostyles (Figure 5 B, C), 105–(130±16)–146 x 5 – (8±2)–10 µm and short; thick and wing-shaped toxas, 45–(57±6)–71 µm (Figure 5 C–D). Few rare and big toxas (250–370 µm) were also found (Figure 5 D).

Distribution. This species has a wide distribution in the SW Atlantic Ocean and southern Pacific, recorded from Antarctic waters, South Georgia Islands, Malvinas (Falklands) Islands, off Buenos Aires and Uruguay, Macquarie Island and New Zealand, (Hooper 2009; Schejter et al. 2011). This is the first record for Burdwood Bank.

Remarks. The synonymy of this species comprises ten alternative names (Hooper 2009) which may reflect the intrinsic variability of the species. Koltun (1976) synonymized Stylostichon tuberculata Burton, Clathria pauper Brøndsted and Microciona basispinosa Burton together with Pseudanchinoe toxifera (Topsent). Later, Hooper (1996) demonstrated that “ antarctica ” should be used against “ toxifera ”, and confirmed the synonymy between “ basispinosa ” and “ toxifera ”, rejecting the inclusion of C. pauper; however, he did not confirm the inclusion of “ tuberculata ” because the types were not found. Also, the new combination proposed for this taxon was Clathria (Microciona) antarctica (Topsent). Goodwin et al. (2011) discussed the synonymy of this species, and considered Clathria (Dendrocia) tuberculata (Burton) as a possible valid species, and recorded it from Malvinas (Falklands) Islands. We assigned our specimens to C. (M.) antarctica (Topsent), considering the synonymy proposed, and also, because “ tuberculata ” was recorded in shallower waters. Other encrusting specimens recorded by us and published in Schejter et al. (2011) were assigned to C. (M.) antarctica in the shelf break area of the Argentine Sea (at 38° 20.02'S 55° 30.22' W 106 m depth), although the present specimen has larger spicules. The larger toxas found in specimens presently dealt with those figured by Burton (1934) in his specimen of “ Pseudanchinoe toxifera ”.

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