Terebellides Sars, 1835
Terebellides sp. 3
Voucher. NIMROD: N1FA.
Diagnosis. Small-sized, slender species, represented by two complete specimens about 10mm long and 0.5mm wide for 18 thoracic and about 30 abdominal chaetigers; body tapering posteriorly; chaetiger 1-10 short, getting progressively longer from chaetiger 11; then segments increasingly shorter and 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 1–5, anterior margins separated from body wall; a swollen glandular area particularly pronounced in chaetiger 1. Nephridial papillae or nephridial pores not observed (using light microscopy).
Branchiae arising as a single structure from segments 3–4, consisting of a single mid-dorsal stalked structure made up of 4 lobes; lobes free of each other; anterior pair larger, the posterior pair shorter than anterior pair; lamellae of branchial lobes loose (=not compacted).
Eighteen pairs of notopodia (segments 3–20), compact, rectangular; notopodia of segment 3 (=1st pair of notopodia) much smaller than on subsequent segments; notopodia of segments 4-7 (2nd – 5th pair) appear 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. Neuropodial uncini in single rows throughout. First thoracic neuropodia (chaetiger 6) with 4-5, sharply bent, geniculate acicular hooks with acute, slightly upward turned tips. Second and all subsequent thoracic neuropodia with about 6 uncini per torus; uncini long handled denticulate hooks with main fang large and surmounted by a crest of smaller denticles. About 30 abdominal uncinigers. Abdominal uncinigers with about 10 avicular uncini per torus, each uncinus with 3–4 teeth above main fang surmounted by number of smaller teeth. Pygidium terminally with 4 very small lobes.
Remarks. These specimens are similar to Terebellides sp. 2 also recorded from Falkland Island in this study, but are smaller and more slender and their branchial lobes are free. The other species with free lobes recorded form Falkland Islands here, Terebellides sp. 1 differs in body shape (with robust abdomen), lappets on 4 not 5 chaetigers and presence of papillae on some chaetigers (see also comments under entry Terebellides sp. 1).
