Amphibian sex determination and sex reversal

Amphibians employ a genetic mechanism of sex determination, according to al l available information on sex chromosomes or breeding tests. Sex reversal allows breeding tests to establish which sex is heterogametic and provides an indication of the mechanism of sex determination. Cases of spontaneous a nd experimental sex reversal (by temperature. hormones or surgery) are revi ewed and illustrated by previously un-published studies on crested newts. T hese newts respond conventionary to temperature and hormone treatment but p rovide anomalous results from breeding tests. It is suggested that both the evolution from temperature dependency to a genetic switch and from ZZ/ZW t o XX/XY are superimposed on a generally uniform mechanism of sex determinat ion in all vertebrates.