Dolphins have very acute hearing, and a brain that is much better able to process sounds than the human one. This is one of the many internal physiological structures leading scientists to believe that dolphins and whales evolved from a terrestrial ancestor. The majority of digestion is processed in the main stomach or second chamber. Research on Dolphins. Scientists are still unclear, however, whether or not dolphins have color vision. Water conducts heat away from the dolphin's body twenty-five times more efficiently than air. Digestive System. Scientists believe evolution holds the key to the answer. Biology of Marine Mammals. It is believed the Odontocete suborder contains many more families than the Mysticete sub order for several reasons. Because the veins surrounding arteries cannot conduct such a large flow of blood back into the body, some blood must return along the peripheral veins close to the surface of the skin. When looking at things below the surface of the water, an oily glandular secretion helps protect a dolphin’s eyes from the elements. Basilosaurus was, in fact, fully aquatic.

Through time, they have become one of the most well equipped and efficient creatures of the sea. Another clue indicating a more powerful upstroke than downstroke is the muscle movement. The Odontocete suborder has ten families, including the family Delphinidae, to which dolphins belong. Dolphins and whales belong to the order Cetartiodactyla, which includes all of the even-toed ungulates. As the dolphin matures, the spots get darker. All mammals are warm blooded, which means they can regulate their own internal body temperature. The whale then uses its tongue to gather and swallow all of the trapped food inside its mouth. This study produced quantitative descriptions of muscle fiber architecture, fiber type composition, and biochemical properties of tendons associated with dolphin locomotion.
Dolphins put a large amount of energy into raising their young, which stay with them an average of three to six years. When resurfacing, a dolphin’s heartbeat can skyrocket to 120 beats per minute. The process is called counter-current heat exchange. A dolphin has very pliant skin. University of California Press: Berkeley and Los Angeles, CA. The upstroke is believed to be the more powerful stroke for a dolphin. Reynolds III, J.E., R.S. These renules all function as separate kidneys which help filter out the higher amount of salt content they must deal with in their daily environment. About 38 to 45 million years ago, Basilosaurus, the largest known advanced Archaeocete, appeared. Odontocetes include all of the toothed whales. The following references are good sources for further information regarding the incredible physiology of cetaceans. Bryden, M. M. and R. Harrison, ed. Dolphins belong to the family Delphinidae, while porpoises belong to the family Phoecinidae. Berta, A. and J. L. Sumich. The family Delphinidae made its appearance around 11 million years ago, while the bottlenose dolphin emerged only about 2-5 million years ago. You can get the book or just download the first section for free here. This gap allows the baby to latch on to the mother’s nipple without biting her. Scientists have recently discovered ancient whale skeletons in Pakistan with well-preserved anklebones displaying features similar to that of the Artiodactyl group. The skull shape also suggests that Mysticete probably do not possess any echolocation capabilities. Where does a dolphin store its oxygen when it dives? Interesting Facts.

Because oxygen is already stored within the muscle tissue, dolphins can slow down their blood circulation to a minimum. The goose beak is an evolutionarily modified larynx that bridges the gap between the nasal passages and the trachea, and is designed to keep anything but air out of the lungs. We as humans don't have any chambers in our stomachs. The surface layer, or epidermis, of a dolphin’s skin is ten times thicker than any land mammal, and serves as protection against the elements. At a certain depth, high pressure causes a dolphin’s lungs to collapse. The veins and capillaries along the surface of the skin also expand, allowing heat to be released through the surface of the skin. The sinuses in the skull base of the Basilosaurus enlarged, a feature seen also in early toothed and baleen whales. In fact, the trachea and esophagus are completely separated with the aid of an organ called the goose beak. Once again, a larger bone surface area would accommodate a more extensive muscle mass. The Evolutionary Biology of Marine Mammals. There have no hind limbs, but vestigial skeletal remains can sometimes be observed. Ridgeway, S. H. and R. Harrison, ed. The terrestrial ancestor of the cetacean quickly adapted to a new aquatic niche and the evolutionary process continued at a rapid rate. Baleen whales and toothed whales diverged from a common ancestor around 35 million years ago. The thickness is related to the type of environment the dolphin lives in. Instead they have fibrous plates called baleen which they use as sieves to trap their food. They do have two nasal passages underneath the skin, but the septum does not rise all the way to the surface. The retia is a tissue found underneath the ribcage, between the blowhole and dorsal fin area.

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