Seasonal changes in a population of Sacculina carcini Thompson (Crustacea: Rhizocephala) in Scotland

On the basis of studies of seasonal changes in the infection levels of Sacculina carcini in Carcinus maenas a life history for Sacculina at Millport, Scotland is proposed. This life history differs from that proposed by Foxon (1940) in that the externa is considered only to live for one year, the interna subsequently regenerating a new externa. This life cycle receives support from observations on regenerating externa.