Harbor Porpoise
The harbor porpoise (Phocoena phocoena) is one of the smallest and most common cetaceans. Harbor porpoises weigh between 61-77kg (135-170lbs) and are usually 1.5-1.7m (5-5.5ft) long. They are found in northern temperate to sub-arctic waters most often in shallower bays or near shore. Like all porpoises, they differ from their dolphin cousins in the triangular shape of their dorsal fin, their blunt rostrum, and their spade-like, rather than conical, teeth. You can further explore the anatomy of the harbor porpoise below.
The special sensory organs in cetaceans include the eyes, ears, and echolocation system. Unlike pinnipeds, cetaceans spend all their time in the water so their sensory systems do not need to function as well in air. Indeed, as fully aquatic animals, cetaceans have become superbly adapted to take advantage of the physical properties of water.
The integument of a cetacean is more than just fat! Indeed the integument, commonly called blubber, of cetaceans is a very special organ because it performs multiple functions. Blubber is a fat filled tissue which covers the body of the animal and keeps the animal warm in a cold, thermally conductive environment. But blubber is also an energy storage depot and helps streamline the body, reducing drag.
The musculoskeletal system consists of the muscles, bones, ligaments, and tendons. In marine mammals, one of the first noticeable differences during a necropsy is the dark red color of the muscles compared with terrestrial animals.
The digestive system of marine mammals consists of the mouth, esophagus, stomach, small and large intestine, colon, and rectum. Accessory organs are also critical for digestive function including the liver and pancreas.
The cardiopulmonary system includes the heart, blood vessels and blood, blowhole, trachea, bronchi and lungs. These interdependent systems are responsible for picking up and carrying oxygen to the cells of the body and transporting and discarding carbon dioxide.
The lymphoreticular system consists of the spleen, lymphnodes, lymphatic vessels, thymus, and bone marrow. The functions of these systems include immune defense, transport of fats throughout the body, and collection and transport of interstitial fluid (the fluid bathing the cells) back to the circulatory system.
The endocrine system is one of two communication systems that the body uses to convey information from one cell to another – the other is the nervous system. The endocrine system consists of all organs and tissues that secrete hormones.
The nervous system is one of two communication systems that the body uses to convey information from one cell to another – the other is the endocrine system. The nervous system includes the brain, spinal cord and all the peripheral nerves of the body.
The urinary system of the porpoise, like other mammals, consists of paired kidneys, ureters, a urinary bladder, and urethra. Unlike most other mammals however, marine mammals have reniculate, or lobed, kidneys.
The female reproductive system in porpoises is similar to other mammals and is composed of the vagina, uterus, fallopian tubes and paired ovaries. In addition, females also have mammary glands and two mammary teats which are found in slits on either side of the urogenital opening.
Like other mammals, the male reproductive tract of the harbor porpoise and other cetaceans consists of two testes with epididymides (singular epididymis), vasa deferentia (singular vas deferens), prostate, and penis. Unlike many mammals however, the testes are located within the body wall (intra-abdominal) and lack a scrotal sac (this is different than in the sea lion).
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