MITOCHONDRIA DIFFERENTIATION DURING SPERMATOGENESIS IN DROSOPHILA-MELANOGASTER - ULTRASTRUCTURAL ANALYSIS IN THE MALE STERILE MUTANT MS (1) 413

The ultrastructural analysis of the male sterile mutant ms (1) 413 revealed that (a) spermatid differentiation is independent of meiosis; the spermatocytes of this mutant do not divide but develop directly into spermatids having one nucleus and four axonemes. (b) Ms (1) 413 is a timing mutation in which the mitochondria cluster prematurely in the primary spermatocyte but do not form a Nebenkern in the spermatid. (c) Fusion of mitochondria into a Nebenkern is not essential for mitochondrial differentiation in the spermatid; in the ms (1) 413 mutant the mitochondria do not fuse but nevertheless differentiate similarly to the mitochondrial derivatives of the wild type. (d) The differentiation of the nuclear envelope is, apparently, abnormal, as indicated by the following phenomena: lack of chromosomal condensation and spindle formation in the spermatocytes; highly irregular distribution of nuclear envelope annuli, condensed chromatin and perinuclear microtubules in the spermatids; and lack of connection between basal bodies and spermatid nucleus. © 1979 Academic Press, Inc.