Basic anatomy and physiology of teleost fish
The study of fish diseases requires in-depth knowledge of normal anatomy and physiology to assist with the necropsy procedure, as well as clinical pathology to help interpret alterations and their possible causes. Fish constitute the most diverse and numerous group of vertebrates. All their vital functions such as feeding, respiration, movement, growth, reproduction and response to stimuli depend essentially on the surrounding medium – water. The main parameters that affect the physiology and health of the fish are oxygen levels, temperature, dissolved salts and the presence of toxic substances and pathogens.
The functional anatomy of a fish is constituted by organs organised by systems which work in a intrinsic co-ordinated way enabling the individual to perform as a whole. These systems cover the fish and protect it from damage, serve as physical support, enable it to perform certain movements, capture and process food, eliminate waste, breathe, reproduce, integrate its biological processes and relate to the external environment. All these functions enable the fish to survive as an individual and as a species. Fish are poikilotherms* and have low metabolic rates. Their body temperature is usually slightly higher than water temperature, and each species lives within a characteristic temperature range with critical upper and lower limits. Some teleosts have traits that make them more suitable for farming, as a gregarious behaviour, ease for feeding and artificial/assisted spawning and a general “hardiness” which makes them more adaptable to the potential stressing environments associated to culture conditions.