A Closer Look at Fish Anatomy

Author: Terry Newhaven

Fish are cold blooded animals that are found in bodies of water. Fish swim by contracting and expanding their body and tail muscles. Fins are meant for balance and fish use them to steer themselves while swimming. Some fish have scales while others don't have much. There are thousands of fish species in various parts of the world. The species have adapted to the specific environment ranging from the ocean, river, lake or stream. Let's learn more about fish anatomy.
Fins

Fins may be the most important part of fish anatomy. They are meant for balance and movement. Tail fin or caudal works as a propeller. The species of fish with tail fin are very fast swimmers, moving swiftly through the waters. At times, it's also used for mating. Female fish use fins to attract their counterparts. The fin found under its body can stabilize the fish when it's swimming through the waters. Catfish have pelvis fins that not only provide stability but also serve as egg carrier. Pectoral fins are used by fish to steer in the direction they want to go. These fins are found near the gills. Pectoral fins have spines that can serve as defense shield against predators. Dorsal fins found in the back area can also give balance to the body.

• Fin Fish: Detailed description of fins and fin fish.
• Fish Anatomy: There's a diagram with labels plus a description of fins.
• Buoyancy, Fins, & Swimming: The page provides great information on fins.

Reproductive System

Just like humans, fish reproduce sexually which means that they procreate by combining egg and sperm. There are different methods of reproduction from one fish to another. Some fish are hermaphrodite in nature where they contain both ovaries and testes. Almost 97 of fish species are oviparous. The development of embryos occurs outside the body. The female releases egg on rocks or plants and the male rubs its sexual organ on them, emitting sperm. This is where the fertilization process happens. On the other hand, there are some species of fish that are ovoviviparous where the development of embryo happens inside the female. The reproductive cycle of fish varies depending on the species.

• Key Species: An explanation of reproduction in major species.
• Fish Reproduction: Highly detailed description of the process.
• Reproduction: Learn about the process of reproduction in fish.

Skin

The skin of fish is not only composed of scales. It's composed of two layers namely epidermis, and dermis. Scales are found in the middle layer. Many people love fish because of the fascinating colors. The colors are formed by pigment cells located in the dermis. Interestingly, a fish has color controlling nerves. When it's pinched, the color will become more intense. Epidermis is responsible for producing slime which is known to protect the fish. Take note that too much slime can cause illnesses. There are various kinds of illnesses that can happen in the skin like fungi, bacteria, and parasite infection. Under normal circumstances, fish skin should be smooth and complete with scales.

• Fish Skin Research: An overview of fish skin and its functions.
• The Skin: The section provides a good description of the skin of fish.
• Color Changes: The article provides information on color changes in frogs, lizards, and fish.

Vertebrae

The structure of vertebrae varies from species. Normally, it consists of three bone elements like the vertebral arch, pleurocentrum, and intercentrum. Two of the structures are embedded in the cartilage. Ray finned fish resembles the vertebral structures of mammal. Sharks have vertebrae that consist of catilagenous tubes developed from the vertebral arches. It includes structures that fill the gaps of the vertebrae. These structures are filled with calcification. Lampreys have arches but nothing like the others. The arches are discontinuous.

• Fish Skeleton: General overview labeled diagram.
• Skeleton & Muscles: There's a good description on page 18.
• Vertebrate Anatomy: Learn about fish vertebrae in Skeletal Elements, Dermal Bone of Fishes, and Somatic Skeleton.

Jaw

The jaw of the fish would indicate the habits of the species. Fish that lives on the surface and feeds on insect has an upturned mouth. This makes it easier for it to capture its prey. Predator fish has a wide jaw line in comparison to omnivorous fish. There are bottom dwelling fish that has whiskers which act as radars. This can help them to locate food in the dark waters. There are some fishes with suction cup mouth that live at the bottom of the sea. It's much easier for them to feed on algae and plants with the suction cup mouths.

• Jaw Protrusion: Watch these animations to understand how it works.
• More on Fish Anatomy: A general description with information on internal and external anatomy.
• Skeletal Anatomy of Head: An explanation with information on the jaws.

Internal Organs

Man and fish share similarities in terms of structure and function. Fish also have microscopic cells and tissues that perform specific function. The groups of tissues are complex and they form organs. These organs are responsible for basic body functions like respiration, digestion, excretion, and so on. Fish have brain, liver, stomach, and kidneys. Instead of lungs, fish have gills which are used to perform respiration in the water. Fish also have a swim bladder which is not present in humans. Spleen and pancreas in fish are difficult to locate because they are very small.

• Internal Anatomy: Excellent diagram with labels and descriptions of the internal organs.
• Anatomy & Physiology: Covers many areas of fish anatomy including the internal organs.
• Koi: There's good information on the internal anatomy of the fish on Pages 9 & 10.

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