Ghedotti, M.: Unpaired Fins: Derived Genitalia in Fishes

A review of the diversity of genitalia derived from unpaired fins in actinopterygiian fishes is presented. The modifications of the anal fin and urogenital region among actinopterygiians are morphologiacally quite varied. The most commonly known and best understood anal-fin derived genitalia are those of the cyprinodontiform fishes. However, median-fin derived genitalia are found in a wide range of distantly related actinopterygiian taxa. This variation in morphology provides an existing reservoir of information concerning the developmental mechanisms associated with the formation of a genital region along the body axis. Like natural teratology or experimental perturbation of development, natural variation among taxa provides valuable information concerning basic developmental patterns and possible developmental outcomes.