ENVIRONMENTAL AND GENETIC CONTROL OF DIAPAUSE TERMINATION IN DAPHNIA
M.E. Pfrender, H.W. Deng
Abstract:
Revival of sexually produced diapausing eggs is an important component of the life-history of temporary-pond dwelling Daphnia. Diapausing eggs from a temporary-pond population of Daphnia pulex were examined for hatching response in six combinations of two temperatures and three photoperiods. Alternating seven days periods of cold (4 C) and complete dark with seven day treatments of warm temperature (10 C; 17 C) and photoperiod (10L:14D; 14L:10D; 18L:06D) was an effective strategy for terminating diapause. Conditions mimicking the natural pond environment during the early growing season elicited the greatest hatching success. We observed no correlation between size of ephippium and subsequent hatching success or timing of hatching. Both outbred and inbred diapausing eggs showed a significant response to temperature. Genetic variation for hatching response was demonstrated by significant among-family variation in inbred ephippia.
(Department of Biology, University of Oregon, Eugene, OR 97403, USA)