The function of the genital and anal papillae for insemination in Compsura heterura is discussed based on the description of their morphologies at different stages of the life cycle and during copulation and spawning. In males and females both the genital and anal papillae are involved in copulation in C. heterura. A pre-anal organ, anterior to the anus and stretched posteriorly, is present in adult males. The openings of the urinary channel and oviduct are separate in females. During copulation, there is an approximation between the female genital and anal papillae which become temporarily juxtaposed, forming a chamber enclosing the opening of the oviduct, which may also function in sperm capture. During spawning, the lateral edges of the female genital papilla are projected anteriorly, acquiring a tubular shape for oviposition.
Lezama, A. Q., & Malabarba, L. R. (2021). The genital and anal papillae of compsura heterura (Characidae: Cheirodontinae): Morphological structure and possible role in insemination. Neotropical Ichthyology, 19(1), 1–13. https://doi.org/10.1590/1982-0224-2020-0079