Thermoregulation in deep sea diving Mammals

Contents Introduction Ectotherms and Endotherms Thermoregulation in deep sea animals Methods of thermoregulation

Physical adaptations Behavioral adaptations Circulatory adaptations

Physiological changes helping in thermoregulation Vasoconstriction and vasodilation

Nervous control of thermoregulation Chemical thermoregulatory mechanism Conclusion

Introduction

Thermoregulation is the ability of an organism to keep the body temperature in certain limits, even when the surrounding temperature is very different.

On the basis of body temperature organisms can be divide into- Ectotherms Endotherms

Thermoregulation

ECTOTHERMS

Internal body temperature is determined by external environment.

Ex- amphibians, fishes and reptiles.

ENDOTHERMS

Internal body temperature is stable, regardless of external fluctuations.

Ex- birds and mammals

Thermoregulation in deep sea mammals Deep sea mammals can be divided into

following recognised groups- Cetaceans(whales, dolphins and porpoises) Pinnipeds (Seals, walruses) Sirenians (mantatees, and dugongs)

Cetaceans and sirenians are fully aquatic and therefore are obligate ocean dwellers.

Pinnipeds are semiaquatic, they spend the majority of their time in water but need to return to land for mating, breeding molting etc.

Methods of Thermoregulation

Adaptations Physical adaptations Behavioral adaptations Circulatory adaptations

Physical Adaptations

Insulation- aquatic mammals are adapt themselves for thermoregulation using dense fur or blubber to reduce heat loss.

Fur traps the air among the hairs and air provides the insulation and prevent heat loss.

Blubber is a continuous sheet of adipose tissue reinforced by collagen and elastic fibers. It forms a thick layer around the body preventing heat loss.

Behavioral adaptations

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When its cold seals clump together to save their body heat

Haul out in warm in polar areas

It is the temporarily leaving the water . It is necessary for mating and giving birth, predator avoidance and thermoregulation.

Sand flipping.

Animals flip the sand on their backs to get protection against heat and direct sunlight.

Circulatory adaptations

Counter current heat transfer: occurs in tongue of whale and flippers of dolphins.

Artery containing warm blood are in close contact with colder veins resulting in heat transfer to the venous blood returning to the body thus saves heat.

Counter current heat exchange

Physiological changes help in thermoregulation

Vasoconstriction: It is the decrease in superficial blood vessel diameter as a result decrease blood flow to surface cooling the skin ultimately reduce heat loss from the body

Vasodilatation: It is the increase in superficial blood vessel diameter as a result increased blood flow to the surface thus heat is dissipated through the body surface.

Vasoconstriction and Vasodilation

Nervous control of thermoregulation in aquatic mammals

The hypothalamus is a small part of the brain that acts like a thermostat.

There are thermoreceptors in the skin, which measure skin temperature.

Both sets of thermoreceptor send nerve impulses to the hypothalamus if the core or skin temperature is too high or low.

The hypothalamus can then initiate corrective mechanisms.

Chemical thermoregulatory mechanism In extreme cases, long-term exposure to high

temperature, the thyroid gland suppresses thyroxine, which reduces the metabolism.

The hormone adrenaline is released by the adrenal gland. This causes a great increase in metabolic rate, resulting in heat production.

Long-term exposure to low temperatures causes the release of thyroxine by the thyroid gland – this causes sustained increases in metabolism.

Conclusion

Without thermoregulation in organisms cannot maintain its body temperature

In ocean marine mammals, if they don’t have proper thermoregulatory mechanism, they will lose their body heat to surrounding water and go into hypothermia and die

Hypothalamus is the main thermostat which help in maintaining the body at thermal set point.

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