Genus Aphelochaeta
Aphelochaeta sp. 1
Voucher specimens. SEALION: station: 6MFB, 7MFC, 14MFB (juvenile); IFLEXIBLE: station 5MFA; VINSON WEST: station 1MFA.
Diagnosis. Specimen from Sealion 6MFB fragment 6.3mm long with 48 chaetigers. Body cylindrical with thorax slightly domed dorsally. Dorsal edge of parapodial areas forming shallow gutter down each side of the dorsal thorax. Ventrally shallow gutter from mid thoracic region (about chaetiger 10) then down body.
Prostomium conical acutely pointed and pointing dorsally in lateral view. Eyes not observed. Peristomium as wide as long, slightly domed dorsally; 3 annulations more obvious in lateral and ventral view, first and third widest. Dorsal tentacles arising from edge of peristomium and positioned dorsally near the mid-line; first branchiae situated posterior to and in line with the dorsal tentacles. Subsequent branchiae situated dorsal to notochaetae.
Chaetae simple capillaries; in thoracic chaetigers relatively short, length is equivalent to three quarters across body segment or about 3 to 4 chaetigers long; all similar in size, with no obvious differences between noto- and neurochaetae.
Pygidium not observed.
Methyl Green Staining Pattern. Dark band around base of prostomium; peristomium with dark bands on the second and third annulations, thin bands on thoracic chaetigers corresponding to edge of parapodia, this is more obvious in some specimens than others.
Remarks. Aphelochaeta sp. 1 is characterized by the position of the dorsal tentacles, the shape and posture of the prostomium, MGSP. Two species of Aphelochaeta have been recorded from the region–A. cf. longisetosa (Hartmann-Schröder, 1965) from Chile, A. malefica (Elias and Rivero, 2009) from Argentina. The FI specimen differs from A. longisetosa on the position of the dorsal tentacles which in the Chilean species are more lateral and separated, close to the chaetae; the notochaetae are longer than the neuro while in the FI specimens they are approximately the same length. Hartmann-Schröder does not provide any information on the methyl green staining patterns–a technique which has only become common in the last decade. The FI species differs from A. malefica because the peristomium does not extend back into the first chaetiger as in the specimens from the River Plate. Also the MGSP differs between the two species.
Distribution. Found around the Falkland Islands from the upper bathyal (400 m) to mid-slope (1500 m).
