Aglaophamus Kinberg, 1865
Aglaophamus posterobranchus Hartman, 1967
Voucher. INFLEX: station 5MFB.
Diagnosis. Small sized species; voucher incomplete (in two fragments), 29mm long and 2.8mm wide for 53 chaetiger long fragment.
Prostomium somewhat ovate, longer than wide, with a V-shaped posterior margin, extending over the first chaetiger; a pair of nuchal organs near the posterior corners of prostomium; a pair of conical antennae in the anterior corners of the prostomium and a pair of palps inserted posteriorly on ventrum the prostomium. Proboscis not everted. Branchiae (inter-ramal cirri) involute; appearing from chaetiger 9, where very small; getting progressively large, but not very coiled (only distally curved inwards); present until end of 53 chaetiger long fragment, where very small again. Parapodia biramous; unadorned - no particularly enlarged lobes present, with the exception of superior lobe over notopodia, which is erect and enlarged (refer to the image for details). Dorsal cirri small, conical in chaetiger 1; from chaetiger 2 small, conical to slightly oval, similar throughout (refer to the image). Ventral cirri particularly well developed in chaetiger 1, where skittle-shaped (slender, but with wider base and thin distally); small, conical in other chaetigers. Preacicular chaetae stout, short, cross-barred in distal half of the shaft; of the same form in both rami. Postacicular chaetae long (particularly long in neuropodia), stouter spinulose and slender (appearing) smooth chaetae present. Single acicular present in each ramus, acicular with very long, thin tip, distally strongly bent. Pygidium not observed.
Remarks. Of several Aglaophamus species with the late start of branchiae and relatively simple, unadorned parapodia known from the region, the Falkland Island specimen corresponds well to A. posterobranchus (see aslo remarks under Aglaophamus sp. 2 and A. sp. 3). It agrees in the size of specimen, origin of branchiae, shape of prostomium, form of dorsal and ventral cirri and shape of parapodia with rudimentary preacicular lobes in both rami, sharply conical acicular lobes in both rami and presence of superior lobe over notopodia, which is erect and enlarged, even in posterior chaetigers (in 53 chaetigers long fragment). Hartman (1967) reported that branchiae may start from chaetiger 9-13 (most commonly 12) and in some specimens not before chaetiger 16. This variation seems to encompass variation encountered in Aglaophamus specimens collected from Falklands Islands, but upon more thorough examination, some of these were assigned to different morphospecies. Aglaophamus sp. 2 is the most similar to specimen assigned here to A. posterobranchus, but its notopodial cirrus is more developed and of foliose form. Aglaophamus sp. 3 with branchiae from chaetiger 15 or not present in 16 chaetiger long fragment lacked the erect, enlarged lobe above notopodia, which is clearly present (even in anterior chaetigers) in specimen assigned here to A. posterobranchus and reported by Hartman (1967) in holotype. Both Aglaophamus sp. 2 and 3 are represented by very small specimens (2.2-3mm long in <20 chaetigers long fragments) and it is possible that these represent developmental stages. Future molecular studies will be necessary to resolve this problem.
