Calanoid copepod eggs in sea-bottom muds. V. Seasonal changes in hatching of subitaneous and diapause eggs of Tortanus forcipatus

Abstract

A warm-water neritic calanoid copepod, Tortanus forcipatus, has been found to lay two physiologically different types of eggs (subitaneous and diapause eggs), which are separately spawned in response to different seasonal environmental conditions. Subitaneous eggs are produced when the planktonic populations are at their numerical maxima, and are only shed until late summer. After peak spawning, true resting eggs are spawned which undergo diapause for 1 to 3 months. The eggs recover from their diapause around mid-winter, but hatching does not take place until the water temperature at the sea bottom exceeds 15°C in early summer.