Aurospio foodbancsia
Small, spioniform polychaete of near-uniform width, holotype entire, 8.1 mm long for 51 segments, maximum width 0.27mm. Color in alcohol pale yellow, without pigmentatio. Prostomium anteriorly rounded, slightly longer than wide, extending to beginning of chaetiger 2 as a raised keel, without peaks, eyes or occipital tentacle. Nuchal organs indistinct. Palps grooved and extending to one-third body length.
Notopodial lamellae of chaetigers 2–3 enlarged, leafshaped and dorsally pointed, largest on chaetiger 3, shielding branchiae. Notopodial lamellae highly reduced on chaetiger 1, small and rounded on chaetiger 4, with low dorsal crests from chaetiger 9. Neuropodial lamellae of chaetiger 1 reduced to a small lobe, rounded on chaetiger 2, rounded and dorsally projecting on chaetiger 3, thereafter small and rounded. Branchiae on chaetiger 3, absent on all other chaetigers. Branchiae smooth, digiform, smaller than notopodial lamellae, often shielded and difficult to observe. Chaetae of three types: capillaries, hooded hooks and sabre chaetae. Anterior chaetae, to chaetiger 10, exclusively long capillaries, with those in anterior notopodia arranged in two rows, each of approximately seven chaetae. Granulated, thickened sabre chaetae from chaetiger 10, multidentate hooded hooks from chaetiger 11 in neuropodia and chaetiger 32 in notopodia. Hooded hooks, under oil-immersion light microscopy, with four visible teeth above main fang consistently observed; with SEM, hood and shaft covered with fine denticles with a total of 13 teeth observed in two rows. Largest and following two teeth in line, subsequently rows alternating with separation between teeth increasing. Up to five hooded hooks in each fascicle in proximal abdominal segments. Pygidium with one long medio-dorsal cirrus and two short lateral cirri.
Aurospio foodbancsia sp. n has close affinities to the deep-sea species A. dibranchiata with regard the shape of the prostomium, notopodial lamellae and size and starting position of the branchiae. In both species the branchial filaments are reduced to small digiform cirri partly shielded by the relatively large notopodial lamellae. However, in all specimens of A. foodbancsia (n = 445 examined), branchiae were absent from chaetiger 4 and there was no evidence that this was a preservation artifact. Further differences include the more elongated prostomium, the absence of gold peristomial inclusions, the more pointed notopodial lamellae on chaetiger 3 and the position of the hooded hooks, which start on chaetiger 10 in nearly all A. dibranchiata specimens, and on chaetiger 11 in nearly all A. foodbancsia specimens examined. Aurospio foodbancsia differs from A. banyulensis in that the latter species has three branchial pairs starting on chaetiger 3.
16S rRNA gene molecular sequence divergence of _ 25% was observed between populations of A. dibranchiata (locality, abyssal equatorial Pacific) and A. foodbancsia (locality, Antarctic shelf).
Antarctic Peninsula, Bellingshausen and Weddell Seas, Southern Ocean.
Soft, muddy sediments at depths ranging from 550 to 4817 m