REPRODUCTIVE PERFORMANCE OF MALE RABBITS (Oryctolagus cuniculus) CHRONICALLY EXPOSED TO NON-LETHAL DOSE OF METHOMYL

Abstract

Exposure to pesticides entails significant effects on the organisms’ survival. This study was conducted to test whether chronic exposure of male rabbits (Oryctolagus cuniculus) to a non-lethal dose of the insecticide Methomyl (S-methyl N-((methylcarbamoyl)oxy) thioacetimidate) can have adverse effects on their reproductive performance. Male rabbits were treated for 30 days with an oral dose of 2 mg of Methomyl per kilogram body weight. These were then used to impregnate three untreated females. Reproductive performance of males was analyzed taking into account the effect on litter size, mean birth weight of offspring, percentage of embryo loss, percentage mortality of offspring one and two weeks after birth and total reproductive loss. Results showed that the treatment did not reduce the number and mean birth weight of the progeny nor did it cause gross external morphological abnormalities. Based on the counts of corpora lutea, the percentages of embryo loss in the two groups did not differ. However, within one week after birth, a significant increase in mortality of neonates was noted in the treated group and was increased further within the second week after birth. Therefore, the chronic exposure to methomyl did not reduce sperm production and viability; however, it induced dominant lethal mutations in spermatozoa. Those mutations did not affect embryonic development, but they exerted lethal effects on growth and survival of neonates. Hence, the study has generated evidence that Methomyl is mutagenic.