Trichobranchidae Malmgren 1866

Family Trichobranchidae Malmgren, 1866 Diagnosis. Transverse prostomium attached to dorsal surface of upper lip; basal part sometimes with eyespots; distal part restricted to base of upper lip, or extending until near anterior margin of lip. Buccal tentacles of one or two types, uniformly cylindrical and/or distally expanded, spatulate. Peristomium forming lips, sometimes continuing dorsally as narrow annulation; circular, straight to convoluted upper lip, about as long as wide; lower lip short or expanded; peristomial lobes present or not. Short anterior segments, segment 1 frequently not visible dorsally; anterior margin of anterior segments with lobes as low even-length collars covering posterior margins of preceding segments, at least ventrally. Branchiae present, 2–3 pairs beginning from segment 2, each pair with single, thick and elongate, tapered or foliaceous filament on either side of pairs, or all fused in single 4–5 lobed structure originating mid-dorsally between segments 2–3. Anterior body slightly glandular ventrally, smooth and not swollen, ventro-lateral pads or mid-ventral shields absent. Notopodia beginning from segments 3–6, typically terminating at segment 20; short, conical, not bilobed notopodia, chaetae emerging on top. Narrowly-winged notochaetae in both rows throughout. Neuropodia beginning on same segment as notopodia or slightly posteriorly; sessile neuropodia until termination of notopodia, neurochaetae emerging directly from body wall, as foliaceous pinnules after termination of notopodia. Anterior neurochaetae as long handled, acicular uncini, arranged in single, straight rows, sometimes with irregular alignment between uncini; neurochaetae as avicular uncini after termination of notopodia, with secondary teeth originating on top and laterally to main fang; first 1–2 pairs of neuropodia with acicular spines instead of uncini in one genus. Nephridial papillae on segment 3 usually present, other papillae usually inconspicuous. Pygidium smooth to slightly crenulate, sometimes bilobed. Remarks. Trichobranchidae is characterized by the presence of lobes as low ventral collars and neuropodia bearing acicular uncini on thoracic segments. There has been speculation over time as to whether this group should be considered as a family of its own, or a subfamily of Terebellidae (Malmgren 1866; Hessle 1917; Fauvel 1927; Day 1967; Rouse & Pleijel 2001; Garraffoni & Lana 2008). Following Nogueira et al. (2013), the group is treated here as a separate family. Trichobranchidae is a small family, of three genera only, differentiated by the morphology and number of pairs of branchiae. Octobranchus Marion & Bobretzky, 1875 has four pairs of branchiae with variable morphology, Terebellides Sars, 1835 has a single mid-dorsal 1–5 lobed lamellate branchia (Muir 2011) inserted on a branchial stem between segments 2 and 3, while Trichobranchus Malmgren, 1866 has 2–3 pairs of branchiae, each as a single elongate and distally tapered filament on each side. The family has not previously been found on the Great Barrier Reef.Published as part of Hutchings, Pat, Nogueira, João Miguel Matos & Carrerette, Orlemir, 2015, Telothelepodidae, Thelepodidae and Trichobranchidae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia, pp. 240-274 in Zootaxa 4019 (1) on page 258, DOI: 10.11646/zootaxa.4019.1.12, http://zenodo.org/record/25339