Reproductive behavior and morphology of Paraleptophlebia spinosa (Ephemeroptera: Leptophlebiidae): implications of variation in copula duration

Abstract

The reproductive behavior and genital morphology of a leptophlebiid mayfly Paraleptophlebia spinosa Ueno were studied in a population inhabiting a mountain stream in Kyoto, central Japan. Males formed swarms along gravel shores, caught females in the air, and mated on the ground. The distribution of the oviposition sites coincided with that of the swarming sites along the stream shore. The lobes of the male penis were characterized by a shallow pocket opening on the ventral side. The female vestibule formed a square-shaped chamber into which eggs were released from the oviducts. The number of eggs carried by females caught during copulation in the field showed a greater variation than the number of eggs of virgin females. Copula duration was strongly correlated with the number of eggs carried by the female. Significantly short copula duration with spent females (egg loading less than 20% of the estimated fecundity) may indicate that males could identify spent females. Copula duration with partially loaded females (egg loading between 20% and 80% of fecundity), however, was not shorter than that with fully loaded females. Male mating tactics with respect to copula duration and the possibility of kinematic sperm displacement are discussed with reference to the behavioral and morphological characteristics of the species.