ENVIRONMENTAL SEX DETERMINATION IN DAPHNIA MAGNA AND D. PULEX: ABIOTIC DETERMINANTS AND MODULATION BY THE NMDA RECEPTOR ANTAGONIST MK-801
Daphnids are subject to environmental sex determination whereby environmental cues initiate the switch from asexual parthenogenetic reproduction to sexual reproduction. The introduction of males into the population marks the transition to sexual reproduction. We determined the environmental cues necessary for male production in Daphnia magna and D. pulex by examining photoperiod (long day, 16 hrs and short day, 10 hrs) and temperature (16, 18, 20 and 22C). Additionally, we investigated the role of the NMDA receptor in male production with the NMDA receptor antagonist MK-801. Both species produced negligible or no male offspring under long day length regardless of temperature. D. pulex produced males under the short day length all temperatures, with colder temperatures significantly increasing male production. D. magna also produced males under the short day length but with colder temperatures significantly decreasing male production. Results suggest that daphnid male sex determination is triggered by a combination of photoperiodic and temperature cues that suppress the NMDA receptor. Thus, environmental contaminants interacting with the NMDA receptor, or unusual water temperatures, may alter male production with adverse consequences for population maintenance.
Allison Camp (Primary Presenter/Author), North Carolina State University, email@example.com;
Maher Haeba ( Co-Presenter/Co-Author), North Carolina State University, firstname.lastname@example.org;
Gerald LeBlanc ( Co-Presenter/Co-Author), North Carolina State University, email@example.com;