Total sperm ejaculation in monandrous (Papilio machaon) and polyandrous (P. xuthus) swallowtail butterflies (Lepidoptera: Papilionidae) restricted to larval stage-derived nutrients

Abstract

Potential capacities of male swallowtail butterflies for ejaculation containing sperm were examined in laboratory studies in monandrous (Papilio machaon) and polyandrous (P. xuthus) species. Virgin males transferred a spermatophore and accessory substances that corresponded to an average of 2.4% and 2.1% of their body weight at eclosion in P. xuthus and P. machaon, respectively. The spermatophore contained about 41 and 120 eupyrene sperm bundles and 247,000 and 202,000 apyrene spermatozoa for P. xuthus and P. machaon, respectively. Individual eupyrene and apyrene spermatozoa of P. machaon were smaller than those of P. xuthus. However, when the males re mated at two days after the first mating, they produced a spermatophore of 55% and 32% of full size in P. xuthus and P. machaon, respectively. The number of eupyrene sperm bundles in the second spermatophore increased while the apyrene spermatozoa decreased in P. xuthus. The larger number of eupyrene sperm bundles and the relatively smaller number of apyrene spermatozoa in the first and the second mating of P. machaon compared to P. xuthus are discussed from the viewpoint of female monandry and polyandry.