The dorsal fins of males of Ollentodon multipunctatus, Skifiia lemae and Skifiia variegata differ from the dorsal fins of the females. The first 4-5 rays of the male dorsal fins have a spine-like appearance and are separated from each other by a deep notching at the periphery of the fin membrane. The female fin is undifferentiated. The male dorsal is generally higher and longer at the base than the female fin. Similarly, the rays in the male fin are thicker than those in the female. Whereas most rays in the fin are bifurcated twice to form three or four terminal branches, the first five rays in both sexes are primarily single (nonsplit) or bifurcated once. There is no structural difference in the first five rays of the two sexes. The fins of the two genera are alike in structure although the dorsal fin of the male Ollentodon is higher or larger, proportionately, than that of Skiffia.
Proceedings of the Iowa Academy of Science
©1965 Iowa Academy of Science, Inc.
"Sexual Dimorphism in the Dorsal Fins of Ollentodon and Skiffia, Mexican Goodeid Teleosts,"
Proceedings of the Iowa Academy of Science, 72(1), 469-477.
Available at: https://scholarworks.uni.edu/pias/vol72/iss1/67