Neanthes rubicunda (Polychaeta: Nereididae) in the current-swept slope of the Strait of Messina (Mediterranean Sea)

Neanthes rubicunda is a little-known nereidid species, with an east Atlantic, Mediterranean and north-west Indian Ocean distribution. The species was investigated in the Strait of Messina (Italy) from 1993 to 2008 during two ship grab and dredge sampling surveys, and ad hoc SCUBA diving, which provided data on its mesoscale and microscale distribution patterns. Depth distribution was shallower (from 4 to 60 m) and average individual size was more than 50% greater with respect to other Mediterranean populations. The species had average density of 4.1 ± 2.7 ind m−2, from a minimum of 0.15 ind m−2 within 20 m depth to a maximum of 16 ind m−2 up to 60 m. The distribution was asymmetrical on the opposite coastal sides of the Strait of Messina, in accordance with local hydrology and sea floor morphology. Coarse, current-swept sediments represent the elective habitat of N. rubicunda, whose settlement beneath and in the upper side of boulders might represent a strategy to contrast sea floor instability. Gut content, mainly constituted by algal thalli (90%) proved Halopteris filicina, Halopteris scoparia and Jania rubens the most frequently ingested seaweeds. Such algae were also found attached to the worm tube-opening, testifying for an algal-gardening behaviour with a prevalent trophic function. Fertile individuals were observed in May, June and July (sea temperature from 17 to 21°C).