(subclass Actinopterygii, order Atheriniformes)
A small family of freshwater fish, of interest mainly because both males and females have the sex organs directed either to the left or to the right. A ‘left’ male can mate only with a ‘right’ female, and vice versa. There are about three species, none exceeding 12 cm in length, found in southern S. America.
Subjects: Zoology and Animal Sciences.