<em>Abstract</em>.—Fish embryos and larvae are developing, not static, organisms before metamorphosis or transformation to the juvenile form. The means by which embryos and larvae meet physiological challenges posed by their environments and the extent to which evolution shapes the outcome of development is only partially understood. An understanding of these issues can only be approached by coupling the development of form and function over the broad phylogenetic span of fishes. Much work has come forward that describes the development of body form and organ systems, while equally valuable, but often separate, work has emerged that describes the physiology of embryos and larvae. Far fewer composite studies that couple developing form with function are available, and fewer yet have addressed such questions as when, and in what capacity, do developing organs or organ systems function. The evolutionary question also requires a phylogenetic perspective. The reviews that follow this introduction will present current thought that reflects upon the following questions: (1) when is the onset of organ (or organ system) development, and in what physiological capacity do these systems operate among fish embryos and larvae; and (2) are there morphological and physiological specializations that are unique to embryonic and larval fishes, and what are these specializations?
The effects of testosterone and insulin-like growth factor 1 on motor system form and function
