PARENT SESSION
Poster Session # 17: Aquatic Systems.
Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.
Effects of body condition on reproduction in western mosquitofish, Gambusia affinis.
Brooks, Melody*,1, Deaton, Raelynn1, Marsh-Matthews, Edie1, 1 University of Oklahoma, Norman, Oklahoma
ABSTRACT- Energy for current reproduction may come directly from environmental food sources or energy fat stores. Using females that differed in body condition, we examined maternal provisioning with external resources in a livebearing fish by injection of radiolabeled nutrients. Gambusia affinis females were collected from a pond in central Oklahoma, isolated in 3.7 L aquaria and randomly assigned to four food treatments in an attempt to manipulate body condition (flake food, frozen brine shrimp, algae, and dried fish). After 24 days females were injected with tritiated leucine to assay mother-to-embryo transfer of nutrients (measured as embryo radioactivity in disintegrations per minute). Two hours post injection, females were dissected and embryos removed from the ovary, dried, weighed and prepared for liquid scintillation assay. Female condition was determined by extraction of fat with multiple washes of petroleum ether. Body condition differed significantly among food treatments: females fed algae or dried fish were in poorer condition. Despite condition variation, all females showed transfer of radiolabeled nutrients to developing embryos. Females in poorer condition did not show decreased investment in embryos: embryo number, embryo weight, and maternal transfer of nutrients did not vary significantly with body condition. Because reproduction was not compromised by decreased body condition, we suggest that energy-limited females will invest more in current than future reproduction, whereas females in good condition may invest in both.
Key words: body condition, matrotrophy, current reproduction