Marine Mammal Adaptions

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Marine Mammal Adaptions

• Adaptation-
• An anatomical structure, a physiological
  process, or a behavior pattern that makes an
  organism more fit to survive and reproduce in
  competition with other members of its species.-
  E.O. Wilson-

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Integument

• The mammalian integument is a complex,
  multi-layered structure.
• Epidermis Outermost layer, cells are often
  keratinized and provide water proofing.
• Epidermal structures include hair, nails, claws,
  sebaceous (oil) and sweat glands
• Dermis Middle layer, formed by two regions of
  connective tissue
• Papillary dermis has finger-like projections,
  each one carries blood vessels and verves toa
  position near the overlying epidermal cells.
• Reticular dermis forms a connection with the
  underlying hypodermis
• Hypodermis Bottom layer, a more loosely woven
  connective tissue layer

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Integument
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Thermoregulation

• Mammals are homeothermic endotherms with a high
  (36 to 38?C) and stable body temperature.
• Water conducts heat away from the body 25 times
  faster than air.

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Adaptations to deal with this

• Low Surface area to Volume ratio decreases the
  relative area across which heat is lost.
• Marine mammals tend to be large, and therefore
  have a small surface area to volume ratio, thus
  reducing heat loss.

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Insulation

• Fur
• Good in air, but loses most of its insulation
  when wet
• Only the sea otter and fur seals have dense
  enough fur that the skin remains dry under water.
  
• Fat
• Marine mammals use blubber, a thick
  subcutaneous layer of fat for extra insulation
• Blubber can be up to 30 of total body weight.
• Not nearly as effective as dry fur, but better in
  the water.
• Many marine mammals use both for insulation.

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Mammal Insulation
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Hair
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Blubber
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Hair vs. Blubber
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Too Hot

• Marine mammals, may also face the problem of
  excess body heat, especially in tropical regions
  when they are swimming a lot.
• Bypass insulation by transferring heat to areas
  of little insulation
• Pinnipeds the underside of the flippers.
• Cetaceans the fluke, dorsal fin, and flippers

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Counter current heat exchanger
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Drag Reduction

• Adaptations to reduce drag
• Reduce hair, or the guard hairs are the leading
  hairs, they are flattened and thus for a smooth
  surface when wetted.
• Streamlining reduces pressure drag
• The hydrofoil shape is best at reducing pressure
  drag.

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Flipper
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Buoyancy Control

• When a body is submerged in water, it displaces a
  volume of water equivalent to its own volume.
• If the weight of the body is less than or equal
  to the weight of the water it displaces, it
  experiences a net upward force and floats.
• If the weight of the body is greater than the
  weight of the water it displaces it sinks.

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Buoyancy Issues

• Mammals are made of some stuff, bone and muscle,
  that are denser than water.
• Other stuff, like air-filled lungs, body fluids,
  fats, oils and blubber are less dense than water
• Two mechanisms to avoid sinking
• Reduce the amount of muscle and bone
• Increase the amount of air, body fluid, fat, oil
  and blubber.

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Skeletons
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Locomotion

• Muscles pull on bones, which are attached at
  joints, thus creating leverage in order to pull
  water behind the animal and thus thrust it
  forward.
• A lever system can be designed to optimize either
  its force output or the velocity at which it
  moves.
• Fource output is increased by increasing
• The force-in
• The mechanical advantage of the lever system.

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Appendages
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Skull Morphologies

• In pinnipeds, otters and sirenians, the skull
  morphology is very similar to that of a
  terrestrial mammal
• Cetacean skulls are different
• Both odontocetes and mysticetes have a cranial
  elongation of the bones that form the rostrum
  (the snout) and a shortening of the braincase.
• Mysticetes also have a tremendously elongated
  maxilla from which the long sheets of baleen
  hang.
• The nostrils have migrated farther back on the
  head, which helps to breathe while in the water.

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Skull Morphologies
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Respiratory System

• Pressure increases with depth such that every 10m
  is an additional atomosphere of pressure
• At high pressures, nitrogen becomes solvent in
  body tissues. When it comes out of solution it
  can rupture the tissue, causing the bends.
• How do marine mammals avoid this?
• Oxygen is stored in the blood and muscles and air
  is kept out of areas that are in contact with
  blood.
• For this reason many seals actually exhale before
  they dive.
• Marine mammal lungs are reinforced so that they
  dont collapse under the pressure and thus trap
  air where nitrogen could be absorbed into the
  blood.

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Blood vs. Lung O2 Content
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O2 in Blood, Lung and Muscle
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Lung Morphologies
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Breathing in the water. How to keep from choking

• How do deep diving animals keep water from
  entering their nostrils? How do they feed without
  breathing?
• Nostrils close tightly
• Odontocetes the larynx forms an elongated
  goosebeaklike structure that fits rigidly into
  the elongated nasal passage. Food passes around
  the larynx when swallowing and no food or fluids
  enter the respiratory system. The intranarial
  (within nose) position of the larynx effectively
  separates the respiratory tract from the
  digestive tract to a greater extent than that
  found in any other mammal.
• Also allows odontocetes to simultaneously
  echolocate and swallow.

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Dolphin Skull
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Feeding

• Finding food
• In addition to using sight, Pinnipeds and sea
  otters use their whiskers to feel for their food.
• Odontocetes use echolocations, which works even
  in the dark.

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Eating

• Pinniped dentition is very similar to most
  carnivores
• Sirenians use lips and whiskers to gather food
  and lack incisors.
• Constantly grind down their molars by chewing.
  Teeth migrate backward and are constantly being
  replaced.
• Odontocetes feed on individual fish and squid.
• Homodonts (all teeth the same) catch food and
  chew it.
• Swallow by creating suction
• Mysticetes lack teeth and use baleen, plates of
  keratinized tissue that hang from their upper
  jaw.

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Teeth
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