Der einfluß der temperatur auf oocytenentwicklung und eiablage bei dem interstitiellen archiannelidenTrilobodrilus axi

The interstitial archiannelidTrilobodrilus axi Westheide 1967 inhabits sandy beaches of the Island of Sylt (North Sea). Spawning occurs from May to July, approximately. Development of oocytes and oviposition occur as soon as the water temperature has risen above 5 °C. In rearing experiments, the influence of temperature on maturation and release of gametes was studied in the female. Animals were collected in winter and reared at temperatures between 3° and 15°C. Within this range, development of oocytes and shedding of eggs were accelerated progressively with increasing test temperatures. Successful reproduction occurred only at temperatures above a critical level (between 3° and 6 °C). It was possible to shift the time of spawning by several months under experimental conditions; this suggests that, in the field, spawning is mainly controlled by temperature. The results indicate thatTrilobodrilus axi is probably a boreo-mediterranean species.