SPERMATOCYSTS IN AEDES AEGYPTI (LINNAEUS)

¹ Department of Entomology, University of Maryland, College Park, Maryland 20740

1. During the larval life of Aedes aegypti (L.), the testes greatly increase in size and numbers of germinal cells, and the number of compartments (or spermato-cysts) increases about five times, to a maximum of 24, usually several days before pupation. Although the germ cells may begin the process of differentiation of spermatids into spermatozoa within the terminal cysts of the testes just before pupation occurs, fully differentiated spermatozoa were never observed in larvae. Generally one testis is smaller than the other in fourth stage larvae, and this difference tends to persist throughout life.

2. Although a significant increase in the number of spermatocysts could not be detected during pupal life, as many as 29 cysts were found among the testes examined during this period. Spermatids may transform into fully differentiated spermatozoa within five hours. While the beginning of differentiation of the spermatids may be delayed for as long as 21 hours after pupation, differentiated sperm were always found after the first 24 hours. The number of differentiated cysts increases during pupal life and it is calculated that 12,000 to 13,000 spermatozoa are formed by both testes. Spermatozoa were never observed in the spermatic ducts during the pupal stage.

3. Although a significant increase in the number of spermatocysts could not be found during adult life, a maximum of 34 cysts were found among newly emerged adults. The number of spermatocysts definitely declines with the age of unmated adults. Spermatozoa begin to fill the postgonadal system during the day of adult emergence. It is estimated that complete filling requires two days, and that the sperm in about 10 cysts are required.

4. When the male uses up most or all of the sperm within his postgonadal system after multiple matings, two to three days are required to replenish the sperm supply. It is suggested that this must involve the formation and maturation of about 11 extra cysts, most of which are needed for replacement within the testes, the others contributing to the supply of postgonadal sperm.