Sublethal effects of cadmium and diazinon on reproduction and larval behavior in zebrafish (Brachydanio rerio)

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Title: Sublethal effects of cadmium and diazinon on reproduction and larval behavior in zebrafish (Brachydanio rerio)
Author: Wall, Steven Barclay
Abstract: For a fish population to survive , it must successfully reproduce . Thus , environmental perturbation of reproductive processes could have significant ecological impacts . Fish are often exposed to lethal and sublethal contaminant concentrations . At sublethal concentrations , there is still a concern that contaminant exposure may influence life history parameters . Sublethal contaminant exposure can impair many reproductive processes , and I was interested in examining the effects of cadmium and diazinon on reproductive success , larval swimming behavior , and a pheromonally regulated steroid . Adult zebrafish (Brachydanio rerio ) were sublethally exposed to either cadmium or diazinon and median spawning time , fecundity , fertilization success , gonadal 17a ,20pdihydroxy - 4 -pregenen -3 -one (DHP ) concentrations (diazinon only ) , gonadosomatic index (GSI ) , median hatching time , hatch success , and larval swimming behavior were monitored . Additionally , larvae were exposed to Cd during embryonic , hatching , and yolk sac stages and exposed to diazinon during a yolk sac stage to monitor larval swimming behavior (swimming speed ) . Cadmium exposure increased median spawning time and male gonadosomatic index (GSI ) ; decreased fecundity , fertilization success , and female GSI ; and altered larval swimming behavior . Diazinon exposure decreased male and female gonadal DHP concentrations , spermiogenesis , and altered larval swimming behavior . However , diazinon , at the sublethal concentrations I measured , did not impair reproduction . Larval swimming speeds in diazinon experiments appeared to follow an hormetic response : low doses increased swimming speeds , but higher doses decreased speeds . Cadmium also inhibited and stimulated larval swimming speed . The most significant swimming alterations in cadmium exposed larvae occurred in the youngest larvae tested (five days post -fertilization ) and during hatching . Whereas cadmium decreased zebrafish reproductive success and diazinon did not , both contaminants affected larval swimming behavior . Swimming behavior is vital to larval survival and altered behavior could increase predation or decrease foraging success . Therefore , a small contaminant -induced alteration in swimming behavior could result in a large decrease in survival .
URI: http : / /hdl .handle .net /2346 /9419
Date: 1999-08

Citation

Wall, Steven Barclay Sublethal effects of cadmium and diazinon on reproduction and larval behavior in zebrafish (Brachydanio rerio). Doctoral dissertation, Texas Tech University. Available electronically from http : / /hdl .handle .net /2346 /9419 .

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