Evaluation of the impact of in‐ovo exposure to dicofol on avian reproduction

Abstract

To assess the possible impact of the currently used organochlorine insecticide, dicofol, on the development and reproduction of avian species, in ovo exposure experiments to its p,p' and o,p' isomers were performed using Japanese quail (Coturnix japonica) eggs. o,p'-Dicofol (0.3-100 µg/g of egg) and p,p'-dicofol (3-100 µg/g) were injected into the yolk prior to incubation and hatched chicks were raised to adulthood. In ovo treatment with o,p'-dicofol impaired the eggshell-forming ability of female quails after sexual maturity; eggshell strength, mass, and thickness were significantly reduced at minimum dosages of 3, 1, and 0.3 µg/g, respectively. o,p'-Dicofol also caused abnormal development of the right oviduct independently of the dose; even a female exposed at the lowest dose tested (0.3 µg/g) possessed a large right oviduct. Minor but significant mass reductions of both the left oviduct and the testis were observed only at 10 µg/g. In addition, the transcript of a gene encoding cytochrome P450 cholesterol side-chain cleavage in the gonads of male hatchlings was markedly reduced by o,p'-dicofol treatment. p,p'-Dicofol did not have any marked effects on the reproductive systems, although some significant changes in eggshell formation and oviduct morphology were observed. The results indicate that transovarian exposure, especially to o,p'-dicofol, could damage avian reproduction mainly through eggshell thinning.

The effects of transovarian exposure to <i>p,p’</i>-DDT and <i>p,p’</i>-DDE on avian reproduction using Japanese quails

“…It has been reported that estrogenic compounds reduce transcription of the CYP11A1 gene in the testis not only of developing embryos but also of adults (Kamata et al, 2009a(Kamata et al, , 2009b(Kamata et al, and 2010Sakaue et al, 2002). The reduced transcription arises at very low in ovo doses of estrogens and was observed in male hatchlings exposed to o,p' -sist into adulthood (Kamata et al, 2009a(Kamata et al, , 2009b.…”

“…PCR analyses of DNA sequences in the sex chromosomes were performed as previously reported (Kamata et al, 2010). Seven female and seven male chicks with no apparent defects were randomly selected from each treatment group at 3 days of age for -ined for gross morphological characteristics.…”

“…Several studies have observed ovary-like tissue in the testis of male chicks, and abnormal retention of the right oviduct, decreased length of the left oviduct and resultant reduced eggshell formation when females matured (Fry and Toone, 1981;Halldin et al, 2003;Holm et al, 2006;Kamata et al, 2009b). o,p'-Dicofol, a minor component of the organochlorine insecticide dicofol with a similar structure to o,p'-DDT and a similar -tion (Kamata et al, 2010). In addition, we reported that the abnormal oviduct of the females treated as embryos with estrogenic compounds exhibited decreased transcriptions of genes encoding calcium binding proteins, which indicated that calcium metabolism for eggshell formation was disrupted (Kamata et al, 2009a).…”