Number of sperm produced and ejaculated by male small yellow Eurema mandarina in summer generations

Abstract

Mating activity of male Eurema mandarina in the summer generation is low shortly after emergence. Changes in the ejaculate potential of virgin males with age were examined for spermatophore mass as well as the number of eupyrene and apyrene spermatozoa produced. Fresh males just after emergence showed little mating activity. Only a single 1-day-old male succeeded in copulating with a virgin female, transferring a small spermatophore of 0.47 mg that contained 7 eupyrene sperm bundles and 47,000 apyrene spermatozoa. Spermatophore mass increased with male age. The number of spermatozoa for both types produced also increased with age. Maximum mass of spermatophore (2.0 mg) was estimated in 14-day-old males, with 107 eupyrene sperm bundles and 650,000 apyrene spermatozoa. The number of sperm transferred to the female was positively related to the number of sperm produced. Older males of more than 14 days old produced and ejaculated larger spermatophore with more sperm than younger males. Because females mate with multiple males, resulting in sperm competition across their mates, older males have higher potential to overcome this situation. The low mating activity of younger males in E. mandarina is a waiting strategy until the accumulation of a full-size spermatophore and a full complement of sperm.