Sterilizing effects of trimethylphosphate in Drosophila melanogaster.

Trimethylphosphate (TMP) causes aspermia in D. melanogaster males. If larvae are allowed to develop on standard maize-meal medium containing 0.002 M TMP or greater, the enclosing adult males, when placed on uncontaminated medium, exhibit a period of temporary sterility. Between test groups the period of sterility is most variable at the doses of 0.002-0.004 M, but at 0.005 M or greater is approximately 11-12 days. Near-lethal doses of about 20 g/kg by abdominal injection produces a temporary sterility in adults, whereas oral doses up to 0.02 M are ineffective. Oogenesis in females is not affected by doses which cause temporary sterility in males. In adult male D. melanogaster, which were treated as larvae with 0.01 M TMP in the food medium, the basal region of testes and seminal vesicles do not contain spermatozoa. Cytological examinations of the spermatids reveal ultrastructural changes which are characteristic of those seen in X/O and sterile-mutant males; they contain incomplete axial fibre complexes, abnormal development of the mitochondrial derivatives, and nuclei which fail to elongate and condense. Evidence from cytological studies of larval testes suggests that the chemosterilizing effect of TMP is upon early primary spermatocytes. This is also supported by mating data.