Spermatophores

Spermatophores are reproductive structures produced by males that enclose or accompany sperm and are used to fertilize a female's eggs. They occur in a variety of invertebrate groups—including insects, arachnids, mollusks, crustaceans, and some echinoderms—and are relatively rare among vertebrates.

They are transferred to the female in several ways: in some species the male deposits a discrete spermatophore on the substrate, and the female gathers it and takes up the sperm; in others, sperm are transferred directly into the female's reproductive tract via specialized copulatory organs such as pedipalps in spiders or intromittent organs in insects. In cephalopods and many mollusks, the spermatophore is a gelatinous capsule that is attached to the female or taken into the female mantle cavity; in Lepidoptera, the spermatophore may also include nutrients that function as a nuptial gift.

Structure varies widely: spermatophores range from simple capsules containing sperm to elaborate masses embedded in mucous or gelatinous matrices. They may contain substances that influence sperm viability or female fecundity, and in some taxa provide nourishment to the female or affect mating frequency.

Because their form and function reflect mating systems and selective pressures on sperm competition and parental investment, spermatophores are of interest in studies of reproductive biology across diverse animal lineages.