Parthenogenic development after chemical treatment of Xenopus laevis spermatozoa.

Eggs of Xenopus laevis were fertilized in vitro by spermatozoa pre-treated with various concentrations of aziridinyl urea (ethyleneurea) for between 30 and 120 minutes. At 2 and 4 mg/ml for 30 minutes there was a high incidence of abnormal embryos, few of which developed into tadpoles; after 6 and 8 mg/ml no tadpoles were produced. However, the highest concentration 10 mg/ml, yielded 66% of tadpoles, only 7% of which were obviously abnormal. With increasing time the same pattern of events was obtained except for a displacement towards the lower concentration ranges. Tadpoles developing from these latter experiments were found to be haploid. The results resemble those obtained by exposure of Rana pipiens spermatozoa to X-rays and ultraviolet light, with the production of gynogenetic embryos, usually referred to as the Hertwig effect.