Occurrence of polyploidy in the fishes

Abstract

Polyploidy, the multiplication of entire sets of chromosomes beyond the normal set of two, has occurred extensively, independently, and is often repeated in many groups of fish, from the sharks to the higher teleosts. While there are several ways that a polyploid fish can develop, environmental change and hybrid stabilization may play a large role in the initiation of a new polyploid species. Despite its prevalence, the importance of polyploidy in the evolution of the fishes is unclear. Polyploidy is more common in the lower teleosts than the higher teleosts, possibly due to an advantage gained through decreased specialization in the lower teleosts, a decreased viability of polyploidy in the higher fish, or both. Polyploid fish could gain an advantage over diploid fish through increased heterozygosity, divergence of duplicate genes, and/or increased expression of key physiological proteins. While polyploid fish do not differ considerably from diploids phenotypically, they may be at a disadvantage, or certain advantages may be lessened due to an overall decrease in cell number. This paper summarizes all polyploid species of fish known to-date, and discusses the possible roles and pathways for establishment of polyploidy in the evolution of the fishes. © 2004 Kluwer Academic Publishers.