Diapause Induction in Daphnia Requires Two Stimuli

Abstract
Short-day photoperiods in conjunction with a second stimulus were required to induce sexual reproduction (and diapause) in an autumnally diapausing strain of Daphnia pulex. The second stimulus was associated with the unalkalized portion of a small lake and with density of the population in laboratory cultures. Diapause was induced at 12° and 19°C.