Induction and Initial Characterization of Male-Sterile Mutants on the Second Chromosome of \u3cem\u3eDrosophila melanogaster\u3c/em\u3e

Fourteen recessive, male-sterile, autosomal mutants of Drosophila melanogaster were induced using ethyl methanesulfonate. The techniques employed restricted the recovery of mutants to those located on the second chromosome. Eleven of the mutants were male-sterile at 23°C, and the remaining three, though fertile at 23°C, were male-sterile at 28°C. Complementation tests involving all possible pairs of mutations showed each to be located in a unique cistron. Spermiogenesis in each mutant was studied by light microscopy to determine the stage at which cellular differentiation deviates from normal and to characterize the associated gross abnormalities. Phase contrast microscopy showed that each mutant sterile at 23°C could be placed in one of four major categories: (I) premeiotic, (II) motile sperm with elongate heads, (III) non-motile sperm with elongate heads, or (IV) non-motile sperm with non-elongate heads. Examination of each temperature-sensitive male-sterile mutant raised at 23°C and 25°C revealed the presence of motile sperm with elongate heads. No observations were made of male homozygotes raised at the restrictive temperature