Levinsenia Mesnil 1897
Levinsenia acutibranchiata (Strelzov, 1973)
Voucher Specimen. Inflex: Station 5MFA
Diagnosis. A small to moderate-sized, long species; voucher specimen incomplete with 112 segments, 18 mm long and 0.3 mm wide; body narrow, slightly expanded in prebranchial region somewhat dorsally flattened in branchial region, cylindrical posteriorly.
Prostomium conical, longer than wide; eyes absent; nuchal organs consisting of 2 short longitudinal slits in the middle of prostomium.
Branchiae from chaetiger 8, 14 pairs (in voucher), first branchial pair rather short with blunt tips, but later pairs getting long tapering distally into acute tips .
Notopodial postsetal lobes short in prebranchial segments, getting longer and cirriform with slightly inflated base in branchial region, becoming very thin in postbranchial regions. Neuropodial postchaetal lobes not observed.
Capillary chaetae of noto- and neurochaetae of prebranchial and branchial regions longest and most dense; postbranchial capillaries thinner and shorter. Modified neurochaetae appear from about chaetiger 25 (in voucher specimen) as a single unidentate spine with well-developed hood on convex side, increasing in number up to 6 per fascicle in posterior segments; size, shape and degree of curvature of spines highly variable within fascicle, usually 2 short heavily curved spines and 4 longer, gently curved spines present; modified neurochaetae accompanied by 2 slender capillaries. Pygidium not observed.
Remarks. Levinsenia acutibranchiata was described by Strelzov (1973) and distinguished from cosmopolitan Levinsenia gracilis by branchiae tapering into acute tips in L. acutibranchiata but blunt in L. gracilis. This feature has also been found in FI specimens. Strelzov (1973) also pointed to differences in notopodial lobes and shape of spines, but the second character appears to be rather variable in L. gracilis to be of value as evident from the images in Strelzov (1973). Additionally subspecies L. gracilis minuta with branchiae with acute tips was described by Hartmann-Schöder (1965) from Chile. Strelzov in his revision (1973) considered her specimens to belong to L. gracilis, he did not comment on the character of branchiae with acute tips and the similarity to L. acutibranchiata. Without access to Chilean specimens of Hartmann-Schröder and Uruguayan specimens of Strelzov, it is difficult to say if these two species are conspecific. We have opted to identify the FI material as Strelzovs species until this issue is resloved.
Distribution. Uruguay shelf at 90 -175m, Falkland Islands.
