Abstract
The structures of the vas deferens and spermatophore, mating behavior, oviposition, and egg-sperm contact were observed in the freshwater shrimp Macrobrachium rosenbergii. The spermatophore consists of paired sperm masses and adhesive and protective matrices. Both matrices are gelatinous, and secreted by the epithelia of the vas deferens. At mating, the spermatophore is transferred from males o females and deposited on the thorax of females between the second and fourth or fifth pereiopods. Spermatozoa are released from the spermatophore at oviposition, and run into the brood chamber of females together with eggs. External fertilization seems to take place in this chamber. Spermatozoa penetrating egg membranes were observed for the first time for caridean shrimps.
