Terebellides Sars, 1835
Terebellides sp. 1
Voucher. NIMROD: station N10FB and N11FA.
Diagnosis. Small-sized species, with complete specimen 6mm long and 0.6mm wide for 18 thoracic and about 30 abdominal chaetigers; body compact, only slightly tapering posteriorly; chaetigers 1-10 short, getting progressively longer from chaetiger 11 for the rest of thorax; abdominal segments short again, getting increasingly crowded towards pygidium.
Prostomium compact; tentacular membrane surrounding the mouth as an enlarged convoluted lobe, buccal tentacles missing. Expanded oblong to rectangular structure (=“lower lip” sensu Hutchings and Peart 2000) below tentacular membrane. Eyespots absent. Lateral lappets on chaetigers 1–4 only slightly enlarged. Small spherical papillae observed dorsally to notopodia of chaetiger 2-4 and 8-10 (visible when specimen Shirla-stained), not confirmed on other segments.
Branchiae arising as a single structure from segments 3–4, consisting of a single mid-dorsal stalked structure made up of at 4 lobes, which are mostly free of each other; anterior pair larger, posterior pair about ½ the length of anterior one; lamellae of each branchial lobe loose (=not compact). Eighteen pairs of notopodia (segments 3–20); first 4 pairs of notopodia slightly smaller than those on subsequent segments. All notochaetae simple, narrowly-limbate capillaries.
Neuropodia present from chaetiger 6 (segment 8). Thoracic neuropodia as sessile pads; abdominal neuropodia as erect pinnules. First thoracic neuropodia (chaetiger 6) with about 5, sharply bent, geniculate acicular hooks with acute tips (completely broken off in voucher N10FB). Second and all subsequent thoracic neuropodia with up to 6 (in voucher N11FA) or 9 (in voucher N10FB) uncini per torus; uncini long-handled, denticulate hooks with main fang surmounted by a crest of smaller denticles. About 30 abdominal uncinigers. Abdominal uncinigers with about 6 (in voucher N11FA) or 10 (in voucher N10FB) avicular uncini per torus, each uncinus with 3–4 teeth above main fang surmounted by number of smaller teeth. Pygidium with 4 equal sized, small lobes.
Remarks. Falkland Island specimen belong to small-sized species, with free branchial lobe and low number of uncini, many of which were described from deep waters. Further work would be necessary to compare these with type material of known species, particularly those from Argentinian and Brazilian basins (Schüller, and Hutchings, 2012).
