Chronic boron or copper deficiency induces limb teratogenesis in Xenopus

Sets of adult male and female Xenopus laevis were administered a boron-deficient (−B) diet under low-boron culture conditions, a boron-supplemented (+B) diet under ambient boron culture conditions, a copper-deficient (−Cu) diet under low-copper culture conditions, or a copper-supplemented (+Cu) diet under ambient copper culture conditions, for 120 d. Adults from each group were subsequently bred, and the progeny were cultured and bred. Results from these studies indicated that although pronounced effects on adult reproduction and early embryo-larval development were noted in the −B F₁ generation, no effects on limb development were observed. No significant effects on reproduction, early embryogenesis, or limb development were noted in the +B group, irrespective of generation. Highly specific forelimb and hindlimb defects, including axial flexures resulting in crossed limbs and reduction deficits, were observed in −B F₂ larvae, but not in the +B F₂ larvae. As was noted in the boron-deficiency studies, significant effects on reproduction and early embryo development were observed in the −Cu F₁ generation, but not in the +Cu F₁ generation. Unlike the effects associated with boron deficiency, maldevelopment of the hindlimbs (32 responders, n=40) was found in the F₁ generation.