Metamorphosis and early larval development of the flatfishes (Pleuronectiformes): an osmoregulatory perspective

Flatfish (Pleuronectiformes) distribution in the environment is influenced by salinity, and varies among species and with developmental stage. Osmoregulatory ability likely plays an important role in defining species and developmental stage-specific distribution. Although the mechanisms of osmoregulation in adult and juvenile teleosts have been widely addressed, far less is known about their larval osmoregulatory physiology. Much of our current understanding of larval fish ion-regulation stems from studies using flatfishes, and this article reviews advances in this field, primarily from the point of view of the developing flatfishes. Addressed here are the ontogeny of salinity tolerance, the development of several important osmoregulatory tissues (the skin, gut, and gill), and the influence of the endocrine system on osmoregulation during early larval development and metamorphosis.