Marine Mammal Physiology and Sensory Systems

Sperm Whales Diving

  • Sperm whales can dive up to 2,000 meters and stay down for up to an hour.
  • Whale watching tours in Kaikoura use hydrophones to track whales and predict their surfacing locations with remarkable accuracy.
  • The tour operators in Kaikoura are always seeking constant improvement.

Physiological Adaptations for Deep Diving

  • Dealing with the Bends:
    • Weddell seals can collapse their trachea to avoid the bends.
    • Bottlenose dolphins collapse their rib cage.
  • Breathing Techniques:
    • Pinnipeds can hyperventilate on the surface to maximize oxygen intake.
    • Marine mammals don't take in as much air as possible before diving; they use other techniques.
  • Neutral Position of Blowhole/Nostrils:
    • Manatees can tightly close off their nostrils.
    • Bottlenose dolphins' neutral position is closing their blowhole, preventing breathing under anesthesia.
  • Alveoli Muscles:
    • Dolphins have muscles around the alveoli to tighten and cut them off from the rest of the lungs.
    • This reduces the potential for gas issues due to pressure changes.
  • Circulatory System Adaptations:
    • Blood is moved to where it's needed most.
    • Oxygen consumption is reduced.
    • Oxygen storage capacity is increased.
    • Bradycardia (slowing down the heart rate) occurs during dives.
    • Blood is shunted to vital organs like the brain and heart.
    • More red blood cells are present.
    • Greater oxygen storage capacity in blood cells is achieved.
    • Muscle tissue has more myoglobin.

Spleen Contraction

  • Weddell seals can contract their spleen when they dive, adding more red blood cells to the bloodstream and increasing oxygen storage.

Excretory System Adaptations

  • Most marine mammals (except freshwater seals and dolphins) live in a marine environment and cannot drink fresh water, necessitating adaptations for osmotic balance and water conservation.
  • They obtain water from metabolizing food.
  • Sea otters sometimes drink seawater, and their kidneys are adapted to extract freshwater from it.
  • Marine mammals have evolved kidneys with multiple lobes (raniculi) to increase surface area for water conservation.
    • Each mini kidney (raniculus, plural raniculi - r\epsilon n\iota culi) has loops of Henle.
    • These kidneys, like the pinniped kidney, can be the same size as a human kidney, but have a greater surface area when unwrapped.
    • The loops of Henle function through countercurrent exchange.
  • "* The loops of Henley are basically a place where the, what's the word I'm looking for, the the concentration is there's a concentration gradient between the the pipe and what's around it."
  • "* And wherever there's a lower concentration and a higher concentration, one is gonna move towards the other one always."
  • Marine mammal excrement is diffuse. Isotopes and genetics can be analyzed from feces.
  • Cyrenians (e.g., Florida manatees) do not typically drink water in saline environments but may drink fresh water from hoses offered by people.

Thermoregulation

  • General regulation involves blubber and fur.
  • Rete Mirabile:
    • A network of arteries and veins for thermoregulation.
    • Arteries carry warm blood from the interior, surrounded by veins carrying cold blood from the extremities.
    • Heat transfers from arteries to veins, warming the returning blood.
    • Countercurrent heat exchange occurs.
  • Behavioral Thermoregulation:
    • Basking in the sun.
    • Rafting (holding flippers in the air).
  • Temperature Regulation Limitations:
    • Polar bears are adapted to super cold temperatures and need temperatures under 50 degrees Fahrenheit.
    • Manatees need warm water above 60 degrees Fahrenheit and suffer from cold stress. They congregate at power plant effluents for warmth.
    • Power plants can impact local water temperatures and algal growth.

Reproduction

  • Females:
    • Have a bicornuate uterus and hidden mammary glands for hydrodynamics.
  • Males:
    • Testes are inside the body cavity to reduce friction.
    • Countercurrent heat exchange cools blood going to the testes.
    • The penis is kept in a pocket and extended when needed.

Sensory Systems

  • Eyes, ears, taste, touch.
  • Tapetum Lucidum:
    • Found in cetaceans, pinnipeds, and sea otters.
    • Amplifies low light.
  • Rods and Cones:
    • Most have rods and cones, but can mostly only see blues and greens.
    • Bottlenose dolphins and California sea lions were subjects of tests.
  • Asiatic river dolphins do not have a lens and cannot see well.
  • The shape of the lens and eye affects vision above and below water. Cetaceans have a round lens that’s better for underwater vision.
  • Pinnipeds also have similarly reshaped lenses and eyeballs.
    • Sirenian and polar bear vision is like other terrestrial mammals.
  • Smell:
    • Cetaceans do not have a sense of smell or olfactory nerves.
    • Pinnipeds and sirenians still have olfactory nerves.
  • Hearing:
    • Cetaceans and sirenians do not have external ears.
    • Cetaceans hear through the lower jaw, which is hollow and filled with fat.
    • The acoustic window (thin bone at the end of the jaw) transmits sound to the ear bones.
  • Lower Jaw and Acoustic Window hearing terms to know.
  • Taste:
    • Pinnipeds and cetaceans cannot taste sweet or sour.
    • Cetaceans are most sensitive near the blowhole, while sirenians and pinnipeds are most sensitive near the vibrissae (around the mouth).
  • Brains
    • Encephalization in the brains of cetaceans and pinnipeds, the shape of a cetacean brain is has lots of folding.
  • Increased auditory cortex may be related the processing of higher amounts of information from the sound.
  • They find Magnetite for detecting magnetic fields, which might be useful for migration.