DELAYED MALE MATURITY IS A COST OF PRODUCING LARGE SPERM IN DROSOPHILA

Among fruit-fly species of the genus Drosophila there is remarkable va riation in sperm length, with some species producing gigantic sperm (e .g., > 10 times total male body length), These flies are also unusual in that males of some species exhibit a prolonged adult nonreproductiv e phase, We document sperm length, body size, and sex-specific ages of reproductive maturity for 42 species of Drosophila and, after control ling for phylogeny, test hypotheses to explain the variation in rates of sexual maturation, Results suggest that delayed male maturity is a cost of producing long sperm. A possible physiological mechanism to ex plain the observed relationship is discussed.