POSSIBLE ROLE OF NONFERTILIZING SPERM AS A NUTRIENT SOURCE FOR FEMALEDROSOPHILA-PSEUDOOBSCURA FROLOVA (DIPTERA, DROSOPHILIDAE)

Males in some insect taxa produce chromosomally or morphologically var iant sperm types, one of which does not fertilize eggs. Hypotheses as to the functional significance of nonfertilizing sperm in these taxa s tate that nonfertilizing sperm may represent nutrient resources utiliz ed by fertilizing sperm, the female mate or the zygote. Drosophila pse udoobscura Frolova males produce two discrete lengths of sperm, short and long, but short sperm do not participate in fertilization. Additio nally, females of this species incorporate C-14 male-derived materials into their tissues. We tested whether these male-derived substances i ncorporated by D. pseudoobscura females originate from nonfertilizing short sperm and could represent a nutrient donation by males. We track ed the fate of C-14 material from the male within female tissues and f ound that females incorporated radiolabel into somatic tissues by six hours after copulation. However, short sperm do not begin to disappear from sperm storage organs until 6 hours after copulation and we found no association between the subsequent loss of short sperm in storage and the amount of male-derived material consequently incorporated into female somatic tissues or oocytes. These results suggest that short n onfertilizing sperm are not the source of C-14 male-derived components incorporated by females and we conclude that short sperm do not serve as nutrient donations to the female mate or the zygote.