Abstract
BackgroundTo date, the genus Amphiduros (Annelida: Hesionidae: Amphidurine) is considered as monotypic. Its single species, Amphiduros fuscescens (Marenzeller, 1875), is well characterised by lacking proboscideal papillae and emerging acicular chaetae, as well as by having three antennae, eight pairs of tentacular cirri and inflated dorsal cirri with characteristic alternating length and colour (transparent, with median orange band and white tips) in live animals.New informationThree specimens, one male and two females, were found below boulders at 5–7 m depth in Punta Santa Anna, Blanes and Cala Maset, Sant Feliu de Guixols (Catalan Sea, NW Mediterranean, Iberian Peninsula). Our finding allowed us to describe different, unreported morphological traits and lead us to support the existence of sexual dimorphism (in terms of colouring, cirri morphology and distribution of sexual products along the body). Despite A. fuscescens having been previously reported from the Atlantic and the Mediterranean (particularly in SE French coasts), the specimens from Blanes represent the first record of the species from the Iberian Peninsula. In addition, our molecular results strongly support that Amphiduros pacificus Hartman, 1961 from California (currently synonymised with A. fuscescens) requires to be re-described and reinstalled as a valid species. In turn, our morphological observations support suggesting all other non-Mediterranean reports of A. fuscescens, including the species still under synonymy (i.e. Amphidrornus izukai Hessle, 1925 and Amphidromus setosus Hessle, 1925) as likely being a cryptic species complex whose the taxonomic status requires further assessment.
Highlights
Amphiduros fuscescens (Marenzeller, 1975) (Annelida: Hesionidae: Amphidurine) appears to be well-characterised by the absence of proboscideal papillae and emerging acicular chaetae, as well as by the presence of three antennae, eight pairs of tentacular cirri and inflated dorsal cirri with characteristic alternating length pattern and in vivo colouring
Despite A. fuscescens having been previously reported from the Atlantic and the Mediterranean, the specimens from Blanes represent the first record of the species from the Iberian Peninsula
Morphology, the available information did not allow Pleijel (2001) to validate the existence of more than one species and it was postulated that this situation ‘goes against common trends in both polychaete and other taxonomies, where species taxa tend to be split, and "cosmopolitan species" are regarded as artifacts which generally disappear on closer inspection’
Summary
Amphiduros fuscescens (Marenzeller, 1975) (Annelida: Hesionidae: Amphidurine) appears to be well-characterised by the absence of proboscideal papillae and emerging acicular chaetae, as well as by the presence of three antennae, eight pairs of tentacular cirri and inflated dorsal cirri with characteristic alternating length pattern and in vivo colouring (transparent, with median orange band and white spots and white tips). Amphiduros fuscescens is known to occur in the North Atlantic Ocean in Brittany (Fage and Legendre 1927) and the Canary Islands (Núñez et al 1997), as well as in the Red Sea (Israelian coasts of the Gulf of Aqaba), the Bismark Sea (Madang, Papua New Guinea), the Coral Sea (Great Barrier Reef, Capricorn Group, Australia) and the North Pacific Ocean (east Honshu and Kagoshima, Japan and from the US west coast to British Columbia) (Pleijel 1993, Pleijel 2001) This wide geographical distribution initially included several populations directly attributed to A. fuscescens, together with three species that were placed under synonymy by Pleijel (2001): Amphidrornus izukai Hesse 1925, Amphidromus setosus Hesse 1925 and Amphiduros pacificus Hartman 1961. Our finding of A. fuscescens in the shallow waters of the Catalan Sea (Iberian Peninsula, NW Mediterranean) allowed us to describe some previously unreported morphological features ( based on living sexually mature specimens), as well as to discuss the taxonomic status and biogeographical distribution of the species and to contribute to the pool of known molecular information on Mediterranean marine fauna
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