Genital structures and spermatophore placement in female Paradiaptominae (Copepoda, Calanoida, Diaptomidae)

The female genital structures of nineteen species of the subfamily Paradiaptominae (Diaptomoidea, Diaptomidae) were studied using light and scanning electron microscopy (SEM). They exhibit a common organization characterized by the absence of seminal receptacles and by the presence of a ventral genital operculum covering the paired gonopores, confirming the general pattern of the Diaptomoidea. The taxonomic value of these structures is analyzed: the shape, size and position of the genital operculum on the genital somite is proposed as a new diagnostic character for the sub-family. The Paradiaptominae species are characterized by a peculiar placement of the spermatophore on the female, in dorsal or laterodorsal position on the urosome. The observations lead to a new hypothesis on the mode of fertilization of the females via a fertilization tube.