Participation of testicular spermatids in development upon intracytoplasmic injection into eggs of the sawfly, Athalia rosae (Insecta, Hymenoptera)

Fertilization by intracytoplasmic injection of mature sperm into mature egg s has previously been achieved in the sawfly, Athalia rosae (Insecta, Hymen optera). In the present study, we examined the potential of spermatids, pre mature male gametes, for participating in development. When round spermatid s and elongating spermatids from pupal testes were injected into the anteri or end of mature eggs, about 5% of the total injected eggs developed into c himeric embryos (independent participation in development of the egg and sp ermatid nuclei). Some of them developed further, hatched, and pupated, with 1-2% of the total injected eggs becoming haploid chimeric male adults in w hich both the egg-derived and injected spermatid-derived nuclei contributed to the germline. No fertilized embryos were obtained by these injections. Elongated spermatids (immature sperm) from newly eclosed adult male testes upon injection did produce fertilized embryos that developed into normal di ploid females (about 7% of the total injected). These results indicate that insect spermatids (round and elongating) have the potential to participate in development, but only independently of the egg nucleus. (C) 2000 Wiley- Liss, Inc.