Self-fertilisation in Celleporella hyalina

Employing recently developed culture methods, 21 colonies of the hermaphroditic bryozoan Celleporella hyalina (L.) established as primary zooids, were grown in isolation for 70 or 79 d before being placed in a communal location, to investigate the possibility of autogamy. Colonies grew rapidly, with compact circular form and a low perimeter:area ratio. Autozooids and sexual zooids were produced as normal. Five colonies produced embryos after 5wk, and only two colonies remained barren for the duration of the isolation period. Placement in communal location was accompanied by substantially increased larval output. In control colonies where isolation was prolonged, brooding activity remained low. Abortion was frequent, and settlement of the few larvae produced in isolation was never observed. It was concluded that although self-fertilisation may be available as an “emergency option”, C. hyalina is routinely outcrossing in nature. The frequent abortion and apparent absence of settlement in autogamous offspring suggest that these offspring may be of reduced fitness.