Basic Anatomy of Species - (Marine)

Osteichthyes, make up the largest of the vertebrate groups with over 20,000 species found in lakes, streams, oceans and estuaries. They have skeletons made of bone as opposed to the cartilaginous fish that have a skeleton made of cartilage, (the same material as in the tops of your ears and end of your nose). Fish are adapted very well for life in the water with body parts that help them move freely, defend themselves, detect food, breathe and sense their surroundings.

The main appendages of fish are their fins, used for locomotion, and to maintain vertical swimming axis (upright form). The top fin is called the Dorsal fin, which gives the fish stability to keep it from rolling over and to assist in movement. The fins on the side of the body are called Pectoral fins which help the fish move up, down and backwards. The fins at the bottom of the fish are known as the Pelvic fins used for breaking the forward motion of the fish. The tail of the fish is known as the Caudal fin which the fish uses for forward momentum typically by sweeping the fin from side to side.

The fishes fins are very important as clues about how the fish live and their habitat. If, for example a fish has a large Forked tail it will be a faster swimmer. There are 6 distinct types of Caudal fin which are exhibited in fish that can be seen in the image below.

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Fish breathe through Gills, which are a feathery structure located behind the eyes which allow fish to extract oxygen from the surrounding water and ‘breathe’. Bony fish have an Operculum to protect their delicate gills. A hard protective structure.

Fish also have a Lateral line this line allows fish to detect tiny vibrations in the water. The line, actually a line of tiny pores in the skin that have microscopic hairs, will begin around the Operculum and run along the body of the fish to the tail. This sense allows the fish to school, evade predators and find prey as well.

Most Chondrichthyes, possess the classical ‘shark shape’ and in appearences alone can be seen as very similar to the bony fish. The sharks possess very similar fins to the bony fish. Caudal fin, Dorsal fin, the Pectoral fins are much less flexible and as such are used only for lift and steering. While the Pelvic fins situated back towards the tail.

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