Determining the Sex of Adult Astyanax mexicanus

INTRODUCTIONThis protocol describes methods for determining the sex of an individual Astyanax mexicanus. Adult males and females differ most obviously in body shape and in form of the anal fin. However, if the sex of an adult cannot be determined by these differences, it can be assessed by testing the anal fin for the presence (or absence) of denticle or hook-like bony elements on the anterior fin rays of the anal fin. These features are observed as an opacity toward the anterior half of the male's anal fin, detected as described in the method presented here.