Amphicteis sp. 1
Ampharetinae Malmgren, 1866
Amphicteis Grube, 1850
Amphicteis sp. 1
Voucher. Sea Lion: station 46MFB
Diagnosis. Voucher is a complete specimen, 14.5mm and 1.2mm. Thorax consists of paleae bearing segment and 17 chaetigers, 14 of these uncinigers; abdomen with 15 uncinigers. Notopodia with capillary chaetae and globular ventral cirrus, present in 17 chaetigers; anterior notopodia smaller, increasing in size from first to fourth pair. Abdominal uncinigers with rudimentary notopodia with rounded distal lobe, abdominal tori with prominent cirriform dorsal cirrus.
Prostomium without paired longitudinal ridges; the middle lobe anteriorly with wide shallow depression, forming short anterolateral horns; paired nuchal ridges straight, well separated by a median gap, arranged at wide angle. Very small pair of light brown eyes present, positioned next to nuchal ridges. Paleae present, pale yellow in colour, 8 per fascicle, extremely long (well past the anterior end of prostomium), stout, slightly curving and gradually tapering into long, thin tip. Buccal tentacles not observed. Four pairs of cirriform branchiae in 2 transverse rows in segments III and IV (forming 2+2 square arrangement), separated by a median gap; branchial styles mostly missing, only 2 present in voucher (on left hand side), both smooth, cylindrical to somewhat flattened (but not truly lamellate), with horizontal striation throughout their length, tapering into blunt tip.
Notochaetae arranged in two groups about 4-5 long, limbate, smooth capillaries with thin tips and similar but much shorter ones. Neuropodial tori with uncini, first and second torus particularly enlarged and producing into short tips dorsally and ventrally, housing around 100 uncini, tori of subsequent uncinigers getting smaller, rounded, posterior thoracic tori housing around 50 uncini. Both thoracic and abdominal uncini with 5 teeth over basal prow in lateral view (although in frontal view some teeth are doubled), rostral tooth not observed. Pygidium with terminal anus and two lateral cirri.
Remarks. Falkland Island specimens are here asigned to the genus Amphicteis, although the longitudinal ridges on prostomium were not observed. The other Amphicteis-like genera - Phyllamphicteis Augener, 1918 (two of four pairs of branchiae lamellate, Paramphicteis Caullery, 1944 (no paleae) and Pseudoamphicteis Hutchings, 1977 (papillose buccal tentacles) are junior synonyms of Amphicteis according to Jirkov (2001). Genus Jugamphicteis Fauchald & Hancock, 1981 lacks longitudinal ridges, but it is also characterised by the presence of fan-like extension on first abdominal segment, which is absent in Falklands specimens.
Amphicteis chilensis Hartmann-Schröder, 1965 is very similar to Falkland Island specimens, but not all characters (such as shape of branchiae) can be varifed as these are missing in all Falkland Island specimen other than voucher, in which only two branchiae are present, others are missing, further not all characters mentioned here were imaged or described by Hartmann-Schröder, 1965. The most noticable difference is in the shape of anterior marging of prostomium, this is concave (with wide shallow depression, forming short anterolateral horns) in FI specimens, while in A. chilensis appears to be convex from the shallow mid depression (Hartmann-Schröder, 1965: p. 247, Fig. 245), dorsum is smooth not annulated as in A. chilensis and additionally rostral tooth in uncini were not observed in Falkland Island specimens and dorsal cirrus in abdominal notopodia is longer. It is probable that Falkland Island specimens represent a new species.
