PARENT SESSION
Oral Session # 3: Fish Ecology.
Presiding: M Ford
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 102.

Effects of food availability on embryo mass and female condition in a livebearing fish.

Deaton, Raelynn ^*,1, Brooks, Melody ¹, Marsh-Matthews, Edie¹, ¹ University of Oklahoma, Norman, Oklahoma

ABSTRACT- Theory suggests that maternal provisioning to embryos should be influenced by resource availability. We examined effects of food availability on embryo mass and female body condition in the largespring gambusia, Gambusia geiseri. This study is part of a larger project investigating factors affecting matrotrophy (mother-to-embryo transfer of nutrients) in live-bearing fishes. Fish were collected from Anson Spring, TX and returned to a greenhouse laboratory at the University of Oklahoma Aquatics Research Facility. Females were randomly assigned to groups of 15 individuals in four feeding treatments, with four replicates per treatment. Feeding treatments were: once every three days, once every two days, once a day, and twice a day. At the end of 30 days, females were euthanized and dissected. Embryos were removed from the ovary, dried and weighed. Female condition was assayed by extraction of fat with multiple washes of petroleum ether. Body condition varied significantly among treatments: females in treatments with low resources weighed less and were in poorer body condition. Body condition did not affect mean embryo mass. Further, embryo mass did not decline with developmental stage, suggesting that maternal transfer of nutrients was sufficient to counter loss of embryo mass due to yolk metabolism. These results suggest that decreased resources did not compromise matrotrophy, despite a clear reduction in female body condition.

Key words: resource availability, matrotrophy, body condition