Chapter 12 - Spermatophore and Sperm Transfer Mechanisms

Abstract

Crustaceans are well known for their varied mating strategies, but the sperm transfer occurs mainly by means of spermatophores. The structural morphology of spermatophores, however, differs significantly among various groups of crustaceans. In the highly evolved decapods such as brachyuran crabs, the spermatophores are simple vesiculate structures that are carried in fluid semen for transference to female during mating. On the other hand, in lobsters and crayfishes, the spermatophores are in the form of sperm masses, enveloped by matrix materials, which are deposited on the ventral sternum of females. In anomuran crabs, the spermatophores are highly complex and generally pedunculate structures, attached to the female body during mating to effect epizoic fertilization. In Crustacea, spermatophores are made of mucoid secretions, produced in various regions of the vas deferens. The mucopolysaccharides contained in the spermatophores may have important roles in hardening of spermatophore layers, protection, maintenance, and perhaps nutrition, of the delicate sperm cells during their prolonged storage on the female body. In the penaeiodean shrimps, the spermatophores have accessory adhesive structures, such as “wings” to enable firm attachment onto the female body. Other forms such as the planktonic copepods, not only show structural complexity of spermatophores but also adopt complicated sperm transfer methods. The evolutionary and ecological significance of spermatophore use in sperm transport in aquatic crustaceans are discussed.