Effects of poecilogony and delayed larval emission on recruitment of subantarctic population of Boccardia polybranchia (Polychaeta : Spionidae)

Populations of the spionid polychaete Boccardia polybranchia were monitored for several years in the intertidal sediments of Kerguelen Island in the s ubantarctic province. This shallow water poecilogonous species exhibited ad elphophagy where the females deposited eggs in capsules of which only 3-5% of the eggs undergo a normal development and fed on the remaining eggs. Typ e I larvae utilized their yolk reserves and fed on nurse eggs. After 8 d a second larval type was visible in the capsules. These Type II larvae presen ted a well developed and functional gut at the third setiger stage and neve r ingested any nurse eggs in the capsules. The consequences of this develop mental pattern were important for recruitment. The number of hatching larva e was considerably reduced, but the protection in the capsules and the posi tion of the capsules within the tubes ensured good local recruitment. Larva l behavior was also modified with the nearly complete lack of a planktonic phase. Dispersal existed for a small number of Type II larvae but the gener al trend led to the formation of dense populations of up to 50,000 ind m(-2 ).