Chapter 4 - Larvae in Fish Development and Evolution

Abstract

This chapter focuses on the development and evolution of fish larvae. The development of fishes from fertilization to sexual maturity is a continuum that is punctuated by developmental events and transitions, which may be either gradual and unremarkable or abrupt and quite dramatic. Freshwater teleost fishes are generally characterized by unspecialized larvae with a gradual transition to the juvenile stage. Some marine teleost fishes develop from demersal eggs and larvae, and these also tend to be unremarkable and have a gradual transition to the juvenile stage. In contrast, the majority of marine teleost fishes have planktonic eggs and larvae, which may have extensive specializations and whose transition to the juvenile stage generally is dramatic. The presence of distinctive features in marine fish larvae (or any group of organisms) would lead one to expect that they are functionally important, that they are the result of natural selection, and that they are thus adaptive. However, unique or unusual features in larvae must be interpreted in the context of the comparative development of the larval, juvenile, and adult stages in order to be considered properly. Further, the adaptive significance of such specializations cannot be determined until structure–function relationships are better understood.