Fish anatomy includes fins, gills, bones, skin, and internal organs. The gills have a cover over them called an operculum and it is used to protect the gills. Agnathas, which are jawless fish such as Sting Rays and Sharks, have gill slits. The water enters through their mouth and then over the gills of the fish. When water passes over the fish’s gills, it allows oxygen to enter the bloodstream and then get sent to various parts of its body. Sharks and Sting Rays both have nostrils, but these are only used for smelling out their next meal, not for breathing.
Another part of fish anatomy are the fins. The fins are used for stability, steering and swimming through the water. There are two fins in particular that help the fish stay stable and keep it from rolling. Those are the anal fins and the dorsal fin. The caudal fin is used to help them to steer and move forward and the pectoral fin also helps them to steer as well as brake in the water. The pelvic fin is used like a leveler to keep them level in the water.
Fish anatomy also includes the shape of the fish. Fish species have about six main body shapes. The flat body shape is found in Flounder, Sting Rays, Sole, and Skates. The fusiform body shape is found in Salmon, Tuna, Barracuda, and Sharks. Round body shapes are porcupine fish while ribbon shapes are found in cutlass. The compressed body shapes are seen in Angel Fish and Butterfly Fish. And the elongated body shape is found in eels, needlefish, and lamprey.
Fish anatomy is not all that complex. They have five senses just as man does, with the exception of the lateral line. The lateral line is simply a series of scales modified by a pore. This pore connects with another system of nerve fibers and sensory cells. The lateral line runs from the gills to the tail and can be seen from the outside. It is the darker line that runs across the center of the fish. It can detect electrical currents in the water and is also used as an echo location in order for it to identify the surroundings. One of the five senses of a fish is vision, which is very limited depending on the conditions of water and lighting. Fish have a highly developed sense of smell and taste which enables them to find their food and know if it is good or not. Fish have a very elevated sense of touch as well. Fish are known to be deaf but some believe that they can hear, although they are not sure whether it is only vibrations felt through the water or actual hearing.