The localisation of lead in the skin of light- and dark-adapted Xenopus laevis

Abstract

Toads pretreated for 2 months on either a dark or a light background were then exposed to lead nitrate at 50 ppm lead for 21 days, the illumination regimes being maintained. Metal analysis of dorsal skin showed significantly higher lead levels (ppp<0.01) in the melanosomes of the dark-adapted toads. The results are consistent with the known affinity of melanin for heavy metals and the documented increase in melanophore number under prolonged dark background regimes. Since all toads received the same lead exposure, the melanosome results give rise to speculation that higher melanin levels might occur in individual melanosomes of dark-adapted skin.