Sigmodota magdarogera O'Loughlin, sp. nov.

Sigmodota magdarogera O’Loughlin sp. nov.

Figures 1–4; key

Material examined. Holotype. Antarctica, Weddell Sea, station ‘North-West Brunt Shelf’, AGT 64, 75.091– 75.09233 ºS, 32.21768– 32.21767ºW, agassiz trawl 610.62–611.83 m, BAS cruise JR275 RRS James Clark Ross, collected by M. Mackenzie et al., 24/02/2012, NHMUK 2014.32.

Paratypes. Antarctica, Weddell Sea, station ‘West Brunt Shelf 2’, AGT 59, 75.2658– 75.26645 ºS, 31.14481– 31.15042 ºW, agassiz trawl 607.1–610.24 m, BAS cruise JR275 RRS James Clark Ross, collected by M. Mackenzie et al., 23/02/2012, NHMUK 2014.33–39 (7), NMV F218844 (1), NMV F218845 (1), NMV F218846 (1).

Diagnosis. Sigmodotid species, vermiform, tapered posteriorly, up to 35 mm long (preserved); conspicuous dorsal and lateral wheel papillae, absent ventrally; 12 peltato-digitate tentacles, four pairs of digits, largest distally; radial plates of calcareous ring with low anterior projection, excavations for tentacular ampullae on outer side of plates, lacking perforation for nerve; single polian vesicle; pair of elongate gonad thin tubes or egg-filled sacs. Ossicles in tentacles rods, predominantly closely spinous along shafts, frequently bifurcate and minutely spinous distally, rarely with branch, rods 240–280 µ m long; ossicles in body wall wheels and sigmoid hooks; wheels clustered into discrete papillae dorsally and laterally, wheels rounded hexagonal with six spokes and teeth around inner rim continuous, posterior body wall wheel diameters 67–123 µ m, anterior body wall wheel diameters 64–168 µ m; sigmoid hooks scattered throughout body wall with very fine outer spinelets on the distal outer hook surfaces, posterior body wall hook lengths typically 133 µ m, anterior body wall hook lengths typically 170 µ m.

Colour. Alcohol-preserved (briefly): yellowish, semi-translucent, white spots (wheel papillae). Preserved: offwhite.

Distribution. Antarctica, Weddell Sea, North-West and West Brunt Shelf, 75ºS, 32ºW, 607– 612 m.

Etymology. Named magdarogera for Magdalena Błażewicz −Paszkowycz (magda) and Roger Bamber (roger) with appreciation of their considerable collaborative contribution to marine invertebrate systematics.

Remarks. Sigmodota magdarogera O’Loughlin sp. nov. is unique amongst Antarctic Sigmodota species by having tentacle rods with closely spinous shafts. The species is also distinguished from other Antarctic Sigmodota species by the combination of tentacle rod lengths, wheel diameters and hook lengths as shown in the key. Specimens are small and damaged and it was not possible to examine ciliated funnels.