Accessory Glands Of Females

Management of Sperm and Other Male Contributions

Sperm management by females involves a wide range of processes, including liberation of sperm from a sperma-tophore, digestion of male secretions and sperm, transport of sperm to and from the spermatheca, maintenance of stored sperm, and fertilization.

Accessory gland secretions can have digestive functions important in sperm management. First, digestive breakdown of the spermatophore can free encapsulated sperm for fertilization and storage. Second, male contributions can provide an important nutritional benefit to their mates. Female secretions can digest the secretory components of male seminal fluid to facilitate a nutritive role. In addition, females can digest unwanted sperm to transform it into nutrients. Third, female secretions in some species are required to digest sperm coverings that inhibit fertilization.

Transfer of sperm to and from the spermatheca is generally accomplished by a combination of chemical signals and muscular contractions. Secretions of female accessory glands in some species increase sperm motility or appear to attract sperm toward the spermathecae. Transport of fluid out through the wall of the spermatheca may also create negative pressure that draws in sperm.

Sperm can be stored for some length of time in sperma-thecae, with the record belonging to ant queens that maintain sperm viability for a decade or more. Secretions of spermathecal glands are poorly characterized, and how sperm is maintained for such extended periods is not known. Spermathecal tissue seems to create a chemical environment that maintains sperm viability, perhaps through reduced metabolism. A nutritional function is also possible.

Transport of sperm out of storage can be facilitated by the secretions of the spermathecal gland, which presumably activate quiescent sperm to move toward the primary reproductive tract. One potential function of female accessory glands that has been explored only slightly is the production of hormonelike substances that modulate reproduction functions.

Production of Egg Coverings

Female accessory glands that produce protective coverings for eggs are termed colleterial glands. Colleterial glands have been best characterized in cockroaches, which produce an oothecal case surrounding their eggs. Interestingly, the left and right glands are anatomically different and have different products. Separation of the chemicals permits reactions to begin only at the time of mixing and ootheca formation. Other protective substances produced by glands include toxins and antibacterials.

Nourishment for Embryos or Larvae

Viviparous insects use accessory glands to provide nourishment directly to developing offspring. Tsetse flies and sheep keds are dipterans that retain single larvae within their reproductive tracts and provide them with nourishment. They give birth to mature larvae ready to pupate. The gland that produces the nourishing secretion, rich in amino acids and lipids, is known as the milk gland. The Pacific beetle roach, Diploptera punctata, is also viviparous and provides its developing embryos with nourishment secreted by the brood sac, an expanded portion of oviduct.

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