Reproductive biology of Boccardia polybranchia (Carazzi) in Kerguelen (Subantarctic Province)

Summary

This work is carried out with samples taken during two southern summers in Kerguelen Archipelago (Southern Indian Ocean). Animals were found in sandy pebbles, in a tidal zone often beaten by the sea and with fresh water incomes. Densities of about 5000 individuals per square meter were found. Body growth and reproduction were observed during the summer period, between December and April. B. polybranchia in this area presents a lecithotrophic type development, with adelphophagy. The general body growth suggests that B. polybranchia has a r-strategy. This adelphophagy and its place in the reproductive strategies is discussed. Examples among Polydorids show that plankotrophic and lecithotrophic types of reproduction can be found and that integration in r- and k-reproductive strategy gradients is difficult. In fact oocyte sizes and amount of produced oocytes are quite variable for given place in the continuum. The transition from the planktotrophic to the lecitotrophic type observed within the same family suggests and adaptation of larvae to food availability resulting from growth arrest of part of the eggs, or from a failure in fertilization of part of the oocyte stock.