Chaetozone Malmgren, 1867
Chaetozone sp. 4
Voucher specimen. LOLIGO: station LFA3.
Diagnosis. Specimen incomplete, 5.5cm long with 35 chaetigers. Body slightly flattened dorso-ventrally, widening only gradually, mid portion of body inflated poorly segmented, posterior abdominal chaetigers concertina like; shallow ventral groove from distal thoracic chaetigers, also weak groove/furrow starting in abdominal chaetigers to end of fragment. Pygidium not observed.
Prostomium and peristomium forming a distinctly triangular appearance. Prostomium triangular with a pointed tip. Peristomium as wide as long, with two distinct annulations, the anterior as wide as long, while the posterior is wider than long. Dorsal tentacles arise laterally in posterior of second annulation. First branchiae situated on an achaetigerous segment immediately distal to the dorsal tentacles. Subsequent branchiae in line with first and situated above the notochaetae.
Thoracic chaetae all capillaries, with two lengths short about 3 chaetigers in length and one or two long ones in excess of 10 chaetigers in length; 5-6 chaetae in notopodia and 4-6 in neuropodia. In proximal abdominal chaetigers notopodia with long and short capillaries. Neuropodia with short, pointed, spine-like capillaries and acicular spines, aciculars occurring in the posterior part of the specimen (possibly about one third down the total body). In proximal chaetigers the acicular and pointed capillaries alternate in position down the fascicule. Acicular spines not observed in the notopodia of the incomplete specimen.
MGSP. No distinct patterns, prostomium does not stain and the remainder of the body only diffusely stains.
Remarks. The distinct body shape of this species, specifically the triangular anterior, separates it from the other FI specimens and from other species recorded from the region. The lack of methyl green staining pattern also marks the species as distinct from Chaetozone sp. 1, sp. 2, sp. 3, sp. 8 and sp. 9. It differs from Chaetozone sp. 6 in the arrangement of the dorsal tentacles which in C. sp. 6 are laterally placed on the peristomium and appear to lie above the first chaetiger.
The presence of a complete achaetigerous segment on which arise the first branchiae is similar to the arrangement found in a number of Chaetozone species (see table in Blake 2015). However the lack of the posterior chaetigers restricts comparison with other species.
