Levinsenia Mesnil 1897
Levinsenia antarctica (Strelzov, 1973)
Voucher specimen. Sea Lion: Station 29MFC
Diagnosis. Long and very slender species; voucher specimens incomplete with 51 segments, 8mm long, 0.3mm wide; body cylindrical, thin, of uniform width; colour white to pale yellow in alcohol.
Prostomium conical, longer than wide, anteriorly rounded, with small terminal papilla; eyes absent; no pigmentation observed; nuchal organs slightly curved slits in middle part of prostomium.
Branchiae from chaetiger 7, 4 pairs in voucher (but varies from 3 to 5 pairs), all short, particularly first and last pair very short (easily overlooked) about twice as long as wide, middle pairs of branchiae longer, about four times as long as wide, all of similar form with blunt tips.
Notopodial postchaetal lobes very small, knob-like in prebranchial segments, becoming larger digiform in branchial segments (but still very small about 1/3 of the length of corresponding branchiae), getting thin in postbranchial region. Neuropodial postchaetal lobes not observed.
Notochaetae always capillaries, longest and dense in anterior part of the body, arranged in single row, not particularly numerous about 10 per fascicle, even fewer in posterior segments. Neurochaetae capillaries similar in form and number to notochaetae, but longer. Modified neurochaetae appear first in chaetiger 17 in voucher specimen as a single, stout, strongly curved (sickle-shaped), straw-coloured to brown spine with unidentate tip and well develop hood on the convex side, these increase to 3 in number in subsequent chaetigers accompanied by two short capillaries, eventually increasing to 5 per fascicle in posterior segments. Pygidium not observed.
Remarks. FI specimens agree well with L. antarctica as described by Strelzov, 1973, although the number of branchiae is more variable 3-5 rather than 3 as reported by Strelzov. This observation agrees with other specimens of this species from Magellan regions as reported by Montiel et al. (2002). Few aberrant specimens agreeing well with L. antarctica, but lacking all branchiae were encountered. Currently, it is assumed that these are damaged specimens in which the branchiae were lost.
Distribution. Southern Ocean (Kemp coast type locality), Weddell Sea, King George Island, Chile (Beagle Channel and Continental slope off Tierra del Fuego) at 100 1162m, Falkland Islands.