Anatomy and Physiology
Marine mammals have a number of physiological and anatomical features to overcome the unique challenges associated with aquatic living. Some of these features are very species specific. Marine mammals have developed a number of features for efficient locomotion such as torpedo shaped bodies to reduce drag; modified limbs for propulsion and steering; tail flukes and dorsal fins for propulsion and balance. Marine mammals are adept at thermoregulation using dense fur or blubber to reduce heat loss; as well as circulatory adjustments to conserve their body temperature (counter-current heat exchangers); torpedo shaped bodies, reduced appendages, and large size to prevent heat loss. Most marine mammals are hypoosmotic and as a result they are constantly losing water to the surrounding environment. They have evolved a number of mechanisms to overcome this, but most retain their water by using highly efficient kidneys, that can concentrate urine. Marine mammals are able to dive for long periods of time. Both pinnipeds and cetaceans have large and complex blood vessel systems which serve to store oxygen to support deep diving. Other important reservoirs include muscles, blood, and the spleen which all have the capacity to hold a high concentration of oxygen. Other features include bradycardia (reduced heart rate), and vasoconstriction (shunts most of the oxygen to vital organs such as the brain and heart) also assist with extended diving and oxygen deprivation. Sound travels differently through water therefore marine mammals have developed a number of ways to ensure effective communication, prey capture, and predator detection. The most notable adaptation is the development of echolocation in whales and dolphins. Lastly, Marine mammals have evolved a number features for feeding, which are mainly seen in their dentition. For example, the cheek teeth of pinniped and odontocetes are designed specifically to capture fish and squid. In contrast, Mysticetes have evolved baleen plates to filter feed plankton and small fish from the water.
Read more about this topic: Marine Mammal
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