Killifish Eggs and Hatchlings

Everything has been busy in the Eco-toxicology Lab getting ready for next week. We've have been dosing the fish eggs with various contaminants trying to find the LC 50 (the point at which half of the eggs are dead). When we have the LC 50 for fish from our control site, we can use that data to compare it to how fish from a contaminated site, the Elizabeth River, deal with the same amount of contamination.

This has been harder then we first expected. The first contaminant we exposed them to was Ammonium Chloride. We tried three dose responses with killifish eggs. In the first experiment, we tried doses ranging from 7.5 mg/L to 150 mg/L. The fish had no reaction and continued with development as usual. We tried another dose ranging from 250 mg/L to 1500 mg/L and once again the killifish eggs showed no response. We did a final, more extreme experiment with doses ranging from 2,500 mg/L to 10,000 mg/L. When the eggs showed no response to this as well, we came to the conclusion that the killifish are protected inside their eggs and that the ammonia does not penetrate the egg. We later did experiments in killifish hatchlings which did show a response to the ammonia. I never thought I'd be happy to say that something died, but after watching many fish eggs survive the ammonia doses, I was glad to deliver the news that hatchlings did show the response we expected to the ammonia and that we would be able to continue on with our research.

Although, this presented an obstacle in continuing with my research of whether Elizabeth River killifish have a fitness cost associated with their adaptation to PAH's. We could no longer do research in eggs because the pesticides we were exposing them to proved to be similar to the ammonia in the sense that the killifish eggs showed no response. Instead we would need to do our research with hatchlings. Killifish eggs take two weeks to hatch. A large quantity of them, 350, will be ready from hatching tomorrow but this set us back a bit in data collection. We will conduct the majority of our research on these hatchlings next week using the data that we have gathered in the last few weeks with the dose response experiments, to know what the correct doses are to reach the LC 50. It will be another busy week, ending of course with the release of the final Harry Potter book. I know many of us in the program are looking foreward to that.