SUBLETHAL EFFECTS OF ESFENVALERATE PULSE-EXPOSURE ON SPAWNING AND NON-SPAWNING AUSTRALIAN CRIMSON-SPOTTED RAINBOWFISH (MELANOTAENIA-FLUVIATILIS)

The spawning activity of the Australian crimson-spotted rainbowfish (M elanotaenia fluviatilis) was monitored over a period of nine days. Aft er the first three days, groups of rainbowfish were pulse-exposed with the pyrethroid insecticide esfenvalerate at one of six nominal concen trations (O, 1, 3.2, 10.0, 32.0, or 100 mu g/L). The effects of esfenv alerate on fecundity, total hatch, hatchability of eggs, frequency of hatch defects, and the survival and growth of subsequent larvae were m onitored. Hepatic cytochrome P-450 activity (ECOD, EROD, EFCOD) was me asured six days post-exposure in controls and fish exposed to 32 mu g/ L esfenvalerate. Cytochrome P-450 activity was also measured in single sex populations of male and female rainbowfish similarly exposed. The effects of esfenvalerate pulse-exposure on the lymphoproliferation of immune cells isolated from spawning and non-spawning groups of rainbo wfish were examined in a second experiment. Over 75% of fish pulse-exp osed to 100 mu g/L esfenvalerate died, and males in all treatments wer e more strongly affected than females. There was a negative correlatio n between pesticide concentration, fecundity, and total hatch. All egg s laid in the first three days post-exposure failed to hatch in some t reatments, although esfenvalerate pulse-exposure did not increase the prevalence of deformed larvae. Esfenvalerate pulse-exposure significan tly increased hepatic ECOD activity in male rainbowfish but had no eff ect on male EROD or EFCOD activities. There was no significant effect of esfenvalerate pulse-exposure on hepatic EROD, ECOD, or EFCOD activi ties of female rainbowfish. Unstimulated lymphocyte proliferation was lower in treated female rainbowfish than non-exposed female fish, and there was some evidence of an interaction with spawning activity.