Fabricinuda sp. 2
Fabricinuda Fitzhugh, 1990
Fabricinuda sp. 2
Voucher. Sea Lion: Station 79MFC.
Diagnosis. Voucher complete specimen (branchial crown missing); body length 6mm; width at fourth chaetiger level 0.3mm; body very narrow, cylindrical, thread-like; preserved specimens pale yellow. Body with eight thoracic and three abdominal chaetigers; chaetiger 12 shortest about as wide as long; chaetiger 38 much longer than wide, increasing in length posteriorly; chaetiger 9 slightly shorter than 8; remaining abdominal chaetigers successively shorter, chaetiger 11 wider than long.
Branchial crown missing. Peristomium with anterior margin of anterior peristomial ring as a low ridge of even height all around, incomplete middorsally not overlapping the higher middorsal conical lobe. Anterior peristomial ring about as long as wide, ventrally with a large square-shaped pad; peristomial eyes not observed (possibly with a pair of very faint black eyes?).
Collar chaetae as very narrowly hooded capillaries; superior thoracic notochaetae elongate, narrowly hooded, around 5-8 per fascicle; inferior thoracic notochaetae of chaetiger 38 bearing up to 3 pseudospatulate chaetae. Thoracic uncini acicular; 8-9 per fascicle arranged in a single irregular row; dark yellow to light brown in colour with large secondary tooth oblique to main fang; apical teeth slender and slightly decreasing in size towards tip of uncinus; small hood present .
Abdominal neuropodia with few very elongated, narrowly hooded chaetae. Abdominal uncini with about 10 rows of teeth in profile, 5 teeth per row; manubrium about the same length as dentate region, slightly expanded proximally; number of uncini per fascicle slightly decreasing posteriorly to 10 on chaetiger 11.
Pygidium conical, longer than chaetiger 11, pygidial eyes not observed .
Remarks. Even though the branchial crown is missing, the characters consistent with genus Fabricinuda Fitzhugh, 1990 were observed, collar present as a low ridge all around, pseudospatulate chaetae present in chaetigers 3-8. This is a second species of Fabricinuda reported from FI material as well as from wider geographical area (Southern Ocean, Magellan region). It differs from Fabricinuda sp. 1 reported from Falkland Islands in possessing a well-developed collar, lack of peristomial eyes (faint at best if present), lack of pygidial eyes and the presence of square-shaped pad on the ventrum of anterior peristomial collar (this character is unique and has not been reported in any other Fabricinuda species). This is only the fourth species of Fabriciidae recorded from the Southern Ocean/Magellan region, yet two new species were found from a single sampling effort, suggesting that improved sampling is likely to discover more of these small, thin bodied worms.
