A redescription of Unobranchus (Annelida: Terebellida: Trichobranchidae), with notes on the systematics of Trichobranchidae

Abstract

Unobranchus abyssalis Hartman, 1965, is redescribed. The genus Unobranchus is synonymised with Terebellides. The genera of Trichobranchidae and possible evolutionary pathways within the family are discussed. Some comments are also given on the relationships of Trichobranchidae and other families of the order Terebellida. Keys are given to the genera of Trichobranchidae and the subfamilies of Terebellidae sensu lato.

A new species of Terebellides (Polychaeta: Trichobranchidae) from Scottish waters with an insight into branchial morphology

“…We follow here Garraffoni and Lana (2004) in preferring to code this character as absence or presence of and "anterior projection" rather than a "fifth lobe", as most recent authors do. If we consider, as Muir (2011) does, that Terebellides has probably evolved from a form with four lateral branchiae, one might expect that the plesiomorphic state in the genus is having four branchial lobes, which later might have evolved to an apomorphic state defined by the presence of a lesser number of lobes.…”

“…3a) may represent a residual extension of the coelomic cavity of SG2; this may, in turn, indicate that this organ may be derived from an hypothetical ancestor with three, and not two, pairs of lateral branchiae (Jouin-Toulmond and Hourdez 2006). This point of view has been explicitly rejected by Muir (2011).…”

“…Williams 1984;Solis-Weiss et al 1991;Hutchings and Peart 2000;Garraffoni and Lana 2003;Schüller and Hutchings 2010, 2012Parapar et al 2011Parapar et al , 2013. The branchiae constitute a complex structure and are by far the most characteristic organ of the genus, showing great interspecific variability, being quite different from those of the remaining trichobranchid genera, namely Artacamella Hartman 1955, Trichobranchus Malmgren 1866and Octobranchus Marion and Bobretzky 1875[Unobranchus Hartman 1965 was recently demonstrated to be a senior synonym of Terebellides by Muir (2011)]. Surprisingly, accurate descriptions of the branchiae across Terebellides species are scarce and little attention has been paid to this relevant character for taxonomic issues.…”

Telothelepodidae, Thelepodidae and Trichobranchidae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia

“…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.…”