Reproductive biology of Ophelia barquii (Annelida, Opheliidae) along the Salento Peninsula (Mediterranean Sea, South Italy)

This study investigates two populations of a polychaete identified as Ophelia barquii Fauvel, 1927, collected in two beaches from the Adriatic (Alimini beach) and Ionian (Gallipoli beach) coasts from the Salento Peninsula. Each population was analyzed monthly from April 2017 to March 2018. In both beaches, populational density decreased from April to August with a complete absence of worms from August to the following January. We hypothesize that this trend results from horizontal migration of individuals for reproductive purposes. Sexual maturation was asynchronous between the two populations, with individuals becoming ripe earlier in Alimini than in Gallipoli. Significant differences in body size were recorded between the two populations, with specimens larger in Gallipoli than in Alimini, suggesting that they could belong to different species. However, lifecycle studies performed under laboratory conditions showed that both populations follow a similar developmental path and can cross-fertilize. The larval development featured a very short period of pelagic life, the shortest known so far for any species of Ophelia.