(PW151) Contamination of mummichog (Fundulus heteroclitus) eggs with PCB126 affects the responses of larvae to diazinon.

Couillard, C.1, Lebeuf, M.1, Légaré, B.1, Trottier, S.1, 1 Department of Fisheries and Oceans, Mont-Joli, Quebec, Canada

ABSTRACT- Fish eggs may receive a load of persistent organic compounds during their formation, and be exposed to contaminants present in water after being spawn. The effect of pre-treatment of eggs with 3,3′,4,4′,5 pentachlorobiphenyl (PCB126) on the response of larvae exposed to the organophosphorous pesticide diazinon, was evaluated in mummichog (Fundulus heteroclitus). A few hours after fertilization, eggs were treated topically with a solution of PCB126 in DMSO (Group A), DMSO (Group B) or not treated (Group C). Newly-hatched larvae from Groups A and B were exposed to various concentrations of diazinon in saltwater and Group C larvae to saltwater alone in a 96-h static test with renewal. Diazinon caused an inhibition of cholinesterase (ChE) activity proportional to the concentration, when > 450 ng/L. It also caused a reduction of body length, with an atypical concentration-response relationship: length reduction at the lowest concentration tested (150 ng/L), no effect at intermediate concentrations and reduction at concentrations > 4,800 ng/L. Pre-treatment with PCB126 reduced the inhibition of ChE but increased the severity of the body length reduction in larvae exposed to diazinon. Therefore, low concentrations of diazinon, reduced the body length of marine fish larvae by another mechanism than inhibition of ChE and contamination of the eggs with PCB126 modified the response of larvae to diazinon, increasing the severity of growth retardation.

Key words: diazinon, Fundulus heteroclitus, PCB126, early life stage

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