Ophelina farallonensis
Ophelina Örsted, 1843
Ophelina farallonensis Blake, 2000
Voucher specimens. Sea Lion: Station 53MFC
Diagnosis. Body small, cylindrical, rigid, glossy, sleek in appearance (almost nematode-like) (Plate 1a.), with mid ventral groove throughout; annulations poorly developed; with 18 segments; 4mm long for body and 0.6mm for length of caudal funnel, body 0.3mm wide; colour in alcohol pale yellow to white. Branchiae entirely absent. Prostomium (Plate 1b.) conical tapering into pointed tip bearing a small terminal palpode; pair of very small red eyes appear to be present (Plate 1b.); lateral nuchal organs not conspicuous. Parapodia bi-ramous, very reduced, the last 4 not shortened and crowded. Chaetae all slender capillaries, notochaetae longer than neurochaetae; the chaetae of the last segment longer than in preceding segments. Anal funnel long (approximately 1/5 of total worm length), thin, cylindrical, bearing a slender cirrus positioned ventrally from near posterior end (Plate 1c.); in majority of specimens the anal funnel has been lost.
Remarks. The specimen collected from Falkland Islands agree well with the description of O. farallonensis a deep species from Northern California (Blake, Hilbig & Scott 2000). The future studies, including molecular techniques may confirm if the Falkland Island specimens belong to this species. To complicate matters further, the abranchiate species from northern European Ophelina abranchiata Støp-Bowitz, 1948 was described from the specimen missing the anal funnel and later authors described funnel in O. abranchiata consistent with the one in O. farallonensis (Blake, 2000). In recent work on North Sea Opheliidae, Kongsgrud et al. (2011) reported that the only morphological difference between two species is the size, with adult specimens of O. abranchiata (10 mm long and 0.8 wide) being considerably larger than O. farallonensis (4.5 mm long and 0.35 mm wide). Additionally records of abranchiate opheliid with 30 segments - Ophelina nematoides - from Antarctic waters can be found (Harman 1966). This species (if valid and not described from a damaged specimen) is clearly different from FI material in having a much greater number of segments.
