Osteichthyes

The osteichthyes, or bony fish, represent the largest taxonomic class of vertebrates in the modern world. Fish have evolved to manage essential life processes in water. This has produced particular tissue adaptations, such as gill and scales, and a variety of body forms to exploit various niches in the aquatic environment. Recognition of anatomic features and physiologic processes common among fish is prerequisite to understanding the response of certain organs to injury and the pathophysiologic consequences that follow. Despite those anatomic uniquenesses, fish share a number of pathologies, and common threads exist in the morphologic expression of disease among fish and other vertebrates. Non-infectious diseases include toxic, metabolic, neoplastic, and environmental conditions, while infectious diseases include those causes by viruses, bacteria, fungi, fungus-like protists, mesomycetozoea, and metazoans. Knowledge of fish anatomy and physiology is also critical to the accurate interpretation of tissues so as to avoid misinterpretations and misdiagnoses.