Sperm Transfer and Storage in the Mediterranean Fruit Fly (Diptera: Tephritidae)

We examined several aspects of sperm transfer and storage in the Mediterranean fruit fly, Ceratitis capitata (Wiedemann). We determined how many sperm are available to virgin males, how many sperm they ejaculate, and how many are subsequently stored by females. In addition we established how sperm are allocated between the 2 spermathecae and investigated sperm load and sperm allocation patterns in females captured in the field in Israel. Male testes contained on average 34,300 ± 2,500 sperm cells before copulation and 14,759 ± 1,400 after copulation. Intriguingly, most of this ejaculate never reaches the spermathecae. Spermathecae of once-mated laboratory reared females contained 3,212 ± 212 sperm, similar to the amount found in field-collected females, 3,612 ± 237. Continuous access to males in the laboratory resulted in significantly elevated numbers of stored sperm (on average 5,250 ± 790), indicating that multiple mating is common. The abundance of sperm stored by field-collected females supports this conclusion. Sperm allocation between the spermathecae, in both field and laboratory females, is significantly nonrandom; one organ (either left or right) contains significantly more sperm than expected by chance, suggesting that allocation of sperm is controlled, either by the male or by the female.