Further observations on carbendazim-induced abnormalities of spermatid morphology in rats.

The effects of a microtubule poison, carbendazim, on rat spermiogenesis were examined for abnormalities of nuclei, acrosome and manchette in round and elongating spermatids in Stages VII-XII on days 7.5, 9.5, 10.0 and 10.5 post-treatment using routine electron microscopy. Spermatid nuclear abnormalities were observed in Stages IX-XI on day 9.5 and at greater post-treatment intervals. Nuclear abnormalities included nuclear distortions, various types of nuclear invaginations and abnormal positioning of the modified nuclear envelope. Acrosomal abnormalities were noted on day 7.5 and at greater intervals. Discontinuous, multiple granular and fragmentary acrosomes were observed in Stages VII-XI. In addition, spermatids with complete absence of acrosome (acrosome-deficient spermatids) were observed in Stages VII-X. Poorly-formed and absent ectoplasmic specializations were seen in the cytoplasm of Sertoli cells next to the acrosome-deficient spermatids. A major abnormality of the manchette was irregular positioning of the manchette microtubules in steps 9-11 spermatids on day 9.5 and at greater intervals, which resulted in nuclear invagination. The results indicate that carbendazim induces abnormalities in spermatid morphology that are common to those reported in testes treated with several chemical compounds and in testes of mutant animals.