Spermatheken

Spermatheken, also known as spermaculae, are specialized organs found in many female invertebrates, as well as some primitive vertebrates, that store sperm after mating. These sacs or receptacles are crucial for reproduction as they allow the female to retain sperm for later use, often for extended periods. This enables fertilization to occur when conditions are optimal, or when she has encountered a suitable mate but is not yet ready to ovulate.

The structure and location of spermatheken vary significantly across different species. In insects, they are typically small, sac-like structures connected to the reproductive tract. In some species, there may be a single spermatheka, while others possess multiple. The stored sperm remain viable within the spermatheka, and the female can control the release of sperm to fertilize her eggs. This stored sperm can also be used to inseminate multiple batches of eggs over time, or to select which sperm fertilizes the eggs in cases of multiple matings.

The function of spermatheken is not limited to sperm storage. In some species, the spermatheka may also provide nutrients to the stored sperm, or play a role in sperm selection, ensuring that only the fittest sperm are used for fertilization. The presence and complexity of spermatheken are indicative of the reproductive strategies employed by a species, highlighting the diverse adaptations that have evolved to ensure reproductive success in the animal kingdom.