PARENT SESSION
Agricultural Pesticides in the South and Southeast Poster Session.
Thursday, November 16, 2000
8:00 AM to 12:00 PM
CC West/Center Exhibit Hall

(PHA025) Effect of salinity on the uptake, elimination and toxicity of aldicarb in male and female Japanese medaka (Oryzias latipes).

Bernache, Erin¹, El-Alfy, Abir¹, Schlenk, Daniel¹, ¹

ABSTRACT- Previous studies in our laboratory have shown that salinity enhances the toxicity of aldicarb in several species of euryhaline fish including Japanese medaka. The enhanced toxicity appears to be related to gender and the expression of flavin-containing monooxygenase(s) in the gill which activiate aldicarb to the more potent acetylcholinesterase inhibitor, aldicarb sulfoxide. In order to examine the contributions of other dispositional processes to the salinity-enhanced toxicity of aldicarb, male and female medaka were separately aqueously exposed to the 96hLC10 of 14-C-aldicarb at 3 salinities for 24 hours and then placed in untreated water for 48 hours. Fish were removed at 0, 1,4, 8, 12, 24 and 48 hour time points. Total radioactivity was measure in each fish. There were no significant differences in uptake between males and females at the three salinities. However, elimination half-lifes for males at 1.5‰ salinity were 15.5 h, whereas at 20‰ salinity the rates were 38.1 h. In females, there was no difference in elimination rates between different salinity regimes (30.4 vs 35.0 h). In contrast, toxicity studies indicate females are more sensitive to salinity-enhanced changes in toxicity. Mortality percentage increased in males from 13 ± 5.7% at 1.5‰ to 56 ± 5.7% at 20‰ while in females it increased to 76 ± 5.6%. These data also show that elimination rates of aldicarb may contribute to salinity-enhanced toxicity in male, but not female Japanese medaka.

Key words: Aldicarb, salinity, elimination, uptake