EVOLUTION OF MULTIPLE KINDS OF FEMALE SPERM‐STORAGE ORGANS IN<i>DROSOPHILA</i>

TLDR

Female Drosophilidae possess two sperm‑storage organs—a pair of spermathecae and a single seminal receptacle—and the evolution of these organs and their correlated changes with sperm morphology are discussed. The study examined 113 Drosophila and allied species to describe variation in female sperm‑storage organ use and morphology. The authors surveyed 113 species across Drosophila and related genera, documenting organ use and morphological differences. Ancestrally both organs stored sperm, but the seminal receptacle has become the primary storage organ, with spermatheca loss occurring at least 13 times and rarely regained, while loss of the seminal receptacle occurred only once and is associated with elaborate spermathecae, and the seminal receptacle’s use correlates strongly with sperm length.

Abstract

Females of all species belonging to the family Drosophilidae have two kinds of sperm-storage organs: paired spherical spermathecae and a single elongate tubular seminal receptacle. We examined 113 species belonging to the genus Drosophila and closely allied genera and describe variation in female sperm-storage organ use and morphology. The macroevolutionary pattern of organ dysfunction and morphological divergence suggests that ancestrally both kinds of organs stored sperm. Loss of use of the spermathecae has evolved at least 13 times; evolutionary regain of spermathecal function has rarely if ever occurred. Loss of use of the seminal receptacle has likely occurred only once; in this case, all descendant species possess unusually elaborate spermathecae. Data further indicate that the seminal receptacle is the primary sperm-storage organ in Drosophila. This organ exhibits a pattern of strong correlated evolution with the length of sperm. The evolution of multiple kinds of female sperm-storage organs and the rapidly divergent and correlated evolution of sperm and female reproductive tract morphology are discussed.