Abstract
The female genital structures of 21 calanoid species belonging to the families Candaciidae, Centropagidae, Pontellidae, Sulcanidae, Temoridae and Tortanidae were studied using light and electron microscopy (scanning electron microscopy, transmission electron microscopy). Except the monotypic Sulcanidae, their organization conforms to a common pattern characterized by egg-laying ducts opening through paired adjacent gonopores into a small cavity, the genital atrium, covered by a genital operculum and opening to the outside through a distal atrial slit. No seminal receptacle is present and the seminal products must be stored for a brief period in the genital atrium.The genital structures occupy a well delimited genital area, the main changes in which concern their position on the ventral face of the genital double-somite, and operculum morphology. Their organization and possible mode of operation are compared with those of other calanoid families. A possible correlation between absence of seminal receptacles and mating behaviour is discussed.