Hagfish are also in this class. These detritovores secrete a slimy substance for protection. Osteichthyes first appeared about 395 My ago, in the Early Devonian. The Osteichthyes have bony skeletons. We will discuss several aspects of the fish in Osteichthyes, including their physiology, reproduction and behavior.
Most fish have an excellent sense of smell, and generally good vision.
Hearing canals run down the length of their bodies and can detect slight vibrations in the water. Gills function to exchange gases betweeen a fish and the water. Most fish adjust their buoyancy using a gas-filled swim bladder . Fish physiologically regulate the salinity of their internal fluids. Some fish are poisonous , while others are venomous.