First records of Ptilohyale littoralis (Amphipoda: Hyalidae) and Boccardia proboscidea (Polychaeta: Spionidae) from the coast of the English Channel: habitat use and coexistence with other species

Abstract

This paper presents the first record of Ptilohyale littoralis (Stimpson, 1853) and Boccardia proboscidea (Hartman, 1940) from the French coast of the eastern English Channel. This record is the second for P. littoralis in European waters following a record from the Netherlands, which is suspected as the site of initial introduction from the Atlantic coast of North America. The observed high densities (up to 270 ind. 0.25 m−2), together with the presence of ovigerous females, suggest that the species could be considered as naturalised in the area. Ptilohyale littoralis was consistently found in the same habitat (mussel beds) as Apohyale prevostii (Milne Edwards, 1830). There was an apparent spatial segregation between these two species and the melitid Melita palmata (Montagu, 1804), the latter being associated with boulders covered with mud. Boccardia proboscidea, native from the west coast of North America and Japan, has already been recorded in European waters (Spain, Ireland, North Sea and French coast of Bay of Biscay), but the present record is the first for the English Channel. The species was found inhabiting the same habitat as M. palmata, i.e. boulders covered with mud. Further investigations are, however, needed along the coast of the English Channel and the North Sea to clarify the pathways of introduction and the status (casual, naturalised or invasive) of P. littoralis and B. proboscidea in European waters.