Male pregnancy and the evolution of body segmentation in seahorses and pipefishes

A review is conducted to reveal that body and tail vertebral numbers in fishes of the pipefish and seahorse family can serve as a model for studies of quantitative trait evolution. A quantitative genetic analysis shows that both traits exhibit significantly positive additive genetic variance, suggesting that vertebral counts in pipefish are heritable traits, capable of a response to selection, and might have experienced an interesting history of selection due to male pregnancy.