Abstract.-The morphological adaptation that the first pair of pleopods has experienced in the Caridea group, permits to characterize them as gonopods which are used for transferring spermatophores to the female during the mating. In order to know the function of the pleopods in the transfer of spermatophores during the mating of the rock shrimp Rhynchocinetes typus, it was necessary to determine the morphology of the male pleopods. The analysis of the first pair of pleopods showed a different morphology compared to the subsequent pair of pleopods, and notable adaptative differences in comparison with the typical morphology of other Caridea. These results suggest that both pairs of pleopods are involved in the transfer of spermatophores to the female.

RESUMEN. Se estableció la forma en que los machos del camarón Rhynchocinetes typus transfieren los espermatóforos durante la cópula. La fecundación es externa y durante el apareamiento, el primer y segundo par de pleópodos masculinos tienen una activa participación en la transferencia de espermatóforos al esternito de la hembra. La participación de estos pleópodos se determinó mediante el número de ovocitos fecundados que presentaron hembras que fueron apareadas con machos sexualmente maduros del tipo robustus con el 1º y/o 2º par de pleópodos amputado. Los resultados demostraron que las hembras apareadas con machos sin el primer y segundo par de pleópodos no fueron fecundadas y aquellas que fueron apareadas con machos sin el primer o el segundo par de pleópodos presentaron un 1,82% y 0,04% de ovocitos fecundados respectivamente, en relación a aquellas apareadas con machos sin amputación (100%). Estos resultados indican que ambos pares de pleópodos participan en la transferencia espermática. Palabras clave: crustáceos, apareamiento, gonopodos, pleópodos, fecundación, Rhynchocinetes typus. Spermatophores transference in the rock shrimp Rhynchocinetes typus(Caridea: Rhynchocinetidae)ABSTRACT. The manner in wich males of the rock shrimp Rhynchocinetes typus transfer spermatophores during mating was determined. Fecundation is external. The first and second pair of male pleopods play an active role in the transfer of sperm to the female's sternite. To he participation of these pleopods was determined by amputating the first, second, or both pairs of pleopods of sexually mature males of the type robustus. The number of fertilized eggs in the females was then counted. No fertilization was observed in he females that had mated with males lacking both the first and second pairs of pleopods. Females that had mated with males without either the first or second pair of pleopods presented (1.8% and 0.04%) fewer fertilized eggs than those females that had mated with intact males (100%). These results indicate that both pairs of pleopods participate in the transfer of sperm.