show Abstracthide AbstractWe investigated the role of the Drosophila melanogaster Concentrative nucleoside transporters 1 (cnt1) gene, which is specifically expressed in the testes. The cnt1 mutants exhibited defects in the duration of copulation and spermatid maturation, which significantly impaired male fertility. The most striking effect of the cnt1 mutation in spermatid maturation was an abnormal structure of the sperm tail, in which the formation of major and minor mitochondrial derivatives was disrupted.