Mammals are animals that give birth to young ones and they have mammary glands. The mammary glands of female mammals produce milk for their young ones. Mammals have many characteristics in common, but the most outstanding characteristic is the presence of mammary glands. It is important to note that the term mammal is derived from the words ‘mammary glands’.
There are several species of sharks. The known species number over 500. The discussion on whether sharks are mammals or fish has been going on for sometimes now because some of the characteristics exhibited by sharks are like those of both mammals and fish.
Sharks Are Not Mammals
Although sharks give birth to their young ones like mammals, they are species of fish and not mammal. In fact, this characteristic makes many people classify sharks as mammals. Some animals, such as the platypus are egg-laying mammals. They do not give birth directly. They are however classified as mammals because they feed their young ones on milk from their mammary glands which the sharks do not. Whales are mammals. But since sharks and whales have a large resemblance, many people tend to assume that sharks are also mammals.
What Shark Characteristics Disqualify It from Being a Mammal?
Sharks are cold-blooded. This implies that the body temperatures of sharks are regulated by the surrounding weather and environmental conditions. Mammals are warm-blooded animals. Their temperatures remain constant despite fluctuations in the surrounding weather conditions. The warm-blooded animals, also commonly referred to as endotherm, have mechanisms that help them keep their body temperatures constant. Such mechanisms include shivering and use of their body hairs. Sharks depend on the external environment for their body temperatures.
Furthermore, as earlier stated, mammals feed their young ones with milk from their mammary glands. The sharks do not feed their young ones with milk since they lack mammary glands.
Mammals possess body hair and fur on the surface of their skins. Sharks have scales that help them in their swimming. Whales, which many people consider to be almost related to sharks, have hair on their skin surface. The hairs of whales are so little that they are mostly considered non-existent. As earlier stated, the fur and hair on the bodies of mammals come in handy in regulating their body temperatures.
It should also be noted that mammals breathe through the lungs. Fish use gills to facilitate their breathing. The sharks have gills that aid them in inhalation of oxygen from the water.
Sharks Are Fish
They are different classes of fish depending on a number of characteristics. The jawless fish which do not have well-developed jaws. The bony fish are fish with bones, and most of them have swim bladders. Sharks do not have swim bladders. The last category of fish in this classification is the cartilaginous fish; this is where the sharks belong. The skeleton of cartilaginous fish is composed of cartilage.
As we have seen above, sharks are not mammals. They are a species of fish. They do give birth to their young ones, but that alone does not qualify them to become a mammal. They do resemble the whales, but still, that does not qualify them to be categorized as mammals. Sharks are fish because they lack some of the principal characteristics of mammals but possess most of the characteristics of fish.