Similar to invertebrates, few studies have examined the effects of dioxins on amphibians. In studies involving exposure of eggs, tadpoles, and frogs to dioxins either by direct injection to tissue or water, no significant mortalities or morphological abnormalities have been observed, except for an increased occurrence of lighter pigmentation in some frogs and tadpoles. Eggs and tadpoles eliminate dioxin relatively quickly, and appear to be about 100- to 1000-fold less sensitive to the deleterious effects of dioxin than early life stages of fish. Several explanations have been offered in the literature, including shorter birth cycle (3-6 days in most amphibians compared to 60 days or longer in fish) and reliance by fish on a yolk sac containing maternal lipids for 120 days after hatching, which greatly increases the likelihood for maternal transfer of dioxins.
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