ABSTRACT
This chapter discusses metamorphosis from the Greek metamorphoum, which most simply can be defined as “transform”. Metamorphosis in fish is post-embryonic and involves profound morphological, biochemical and physiological transformations, which prepare the fish for life in a different habitat. The regulation of metamorphosis in lamprey is still enigmatic and appears to be unlike that found in amphibians and flatfish. The chapter aims to integrate information about changes during metamorphosis with experimental evidence indicating when thyroid hormones (THs) intervene and the consequence of this intervention. The implication of THs in immune system maturation in African clawed frog (Rollins-Smith, 1998) suggests they may also play a similar role in teleosts.
