Effects of methoxychlor exposure of flagfish eggs ( Jordanella floridae) on hatchability, juvenile methoxychlor tolerance and whole-body levels of tryptophan, serotonin and 5-hydroxyindoleacetic acid

Abstract

One-day-old flagfish eggs pulse-exposed for 2 h to 0 (control), 0 (ethanol-carrier control), 1.29, 2.58, 3.51 or 5.48 mg l −1 methoxychlor showed respective hatching successes of 92.5, 92.5, 86.3, 77.5, 72.5 and 75.0%. The methoxychlor impact was modified by the age of the eggs at exposure. Two and 3-day-eggs subjected to the same protocol showed 100% hatch for all treatments. Exposure of 1-day-old eggs also reduced the subsequent methoxychlor tolerance of the resulting juveniles. Eight-day-old juveniles hatched from 1-day-old eggs which had been exposed to 0 or 3.51 mg l −1 methoxychlor showed mean 96 h pulse-exposure methoxychlor LC 50s of 3.04 and 0.62 mg l −1 respectively. Conversely, exposure of 3-day-old eggs had no impact on subsequent methoxychlor tolerance of 8-day-old juveniles; 96 h pulse-exposure LC 50s for all treatments ranged from 2.48 to 2.55 mg l −1. Both pre-exposure of 1-day-old eggs and pulse-exposure of 8-day-old juveniles significantly reduced whole-body tryptophan, serotonin and 5-hydroxyindoleacetic acid levels in juvenile flagfish. It was concluded that some form of protective mechanism prevented methoxychlor from affecting the embryo by 48 h post-fertilization. Up to 24 h post-fertilization, however, the embryo was detrimentally affected, as evidenced by reduced hatching success, juvenile tolerance and indoleamine levels.