Abstract
The summer breeding serpulid polychaetes Hydroides fusicola and Pomatoleios kraussii were collected in winter and reared in the laboratory in order to induce winter breeding and to elucidate the effects of environmental factors on gametogenesis.
In both species winter breeding could be induced by exposing individuals to a raised water temperature of 23°C and feeding on an algal food Chaetoceros calcitrans. A number of healthy nectochaetal larvae were obtained by artificial fertilization and the settlement of the larvae on substrata was observed.
The gonial multiplication and growth of oocytes including vitellogenesis were accelerated at the raised water temperature.
Not only the growth of oocytes but also the gonial multiplication at a low temperature of 13°C was accelerated by feeding.
It was assumed that the full maturity in winter was attained about a month after the beginning of the rearing using the algal food at 23°C.
