Effects of saline intake until the second mating on the Ejaculates and Sperm number of male Swallowtail butterfly, Papilio xuthus Linnaeus

Abstract

Although sodium ions induce puddling behavior in males of some butterfly species, the role of sodium ions in the male life history is unclear. Effects of saline intake until the second mating on the mass of spermatophore and accessory substances, as well as the number of eupyrene sperm bundles and apyrene spermatozoa, were examined in the male swallowtail butterfly, Papilio xuthus Linnaeus. The virgin male transferred 6 mg spermatophore and 8 mg accessory substances with 38 eupyrene sperm bundles and 350,000 apyrene spermatozoa to a virgin female during copulation. A small spermatophore, a little accessory substance, and a low number of eupyrene sperm bundles and apyrene spermatozoa in the second mating of mated males the day after the first copulation were found. Mated males fed on both 20% sucrose solution and 0.01M saline solution for two days after the first copulation transferred similar ejaculates at the first copulation. Saline intake recovered the ejaculate mass. Because a large spermatophore and a large number of sperm must be advantageous to the male under sperm competition in female polyandry, puddling behavior might be important to increase reproductive success in males.