Seasonal patterns in the reproductive activity of barnacle-dwelling littorinids

The reproductive activity of a population of barnacle-dwelling littorinids at Peak Steel, on the north east coast of England, was investigated. Variat ion in the number of mature males and females, expressed as a percentage of the whole population, showed: a marked difference among the barnacle-dwell ing littorinids. Littorina neglects displayed a distinct seasonal component to its reproductive activity, with a peak in early summer, Littorina arcan a B also displayed a distinct seasonal component, with a lull in the summer months. However, L. saxatilis B maintained its reproductive activity all y ear, but with an increase in output in the summer. The reproductive activit y of both L. arcana B and L. saxatilis B follow similar patterns of reprodu ctive activity as their typical non barnacle-dwelling forms, suggesting tha t these are true barnacle-dwelling ecotypes. The controversy surrounding th e specific status of L. neglecta is also discussed.