spermatophore

A spermatophore is a capsule or packet containing sperm that is produced by a male animal for transfer to a female during reproduction. Spermatophores are common in many invertebrate groups and can function as an external unit that the female takes up or as a mechanism for direct transfer during mating. In some species, the spermatophore also includes a nutritive or protective component, such as a spermatophylax, which provides nutrients to the female or aids egg production.

Structure and transfer methods vary widely. A typical spermatophore has a protective envelope and a sperm-containing core. In crustaceans, mollusks, and some arachnids, spermatophores are deposited on a surface or onto the female, and fertilization occurs when sperm reach the female’s reproductive tract. In many insects, notably some Lepidoptera (butterflies and moths), the male delivers a spermatophore to the female during mating; the female may digest part of it for nutrients and store or use the sperm for fertilizing eggs. Transfer can involve direct injection during copulation or a transfer via specialized structures.

Taxonomic distribution ranges from crustaceans (e.g., copepods, amphipods, isopods, certain decapods) to mollusks, insects, and several arachnids. Spermatophores illustrate diverse reproductive strategies and confirm that fertilization can occur without direct insemination through copulatory organs in all cases.

In research, spermatophores are studied for insights into mating systems, sperm competition, and the evolution of nuptial gifts and nutrient provisioning.