Marine Bio: hydrodynamics

Archaeoceti: stable isotopes and habitat

  • Isotopes can be found in the teeth b/c what they eat the isotopes will be in their teeth bones

  • Can be used to identify the habitat they spend the most time in (to feed)

  • Larger ranges = estuaries (semi-aquatic to transitional species)

  • Mardern marine and freshwater cetacean as control

  • Pakicetus

    • Freshwater

  • Ambulocetus

    • Transitional (Estuaries)

  • Remingtonocetus and Protocetids

    • Marine

Family Aetiocetidae: Early Mysticetes

  • End of epoch

  • (cranial symmetry) Telescoping

    • beginnings of telescoping

    • Overlap and stretch of the bones

  • Baleen appearance hypothesis

diff/. Lineage whales that evolved

  • Teeth

    • modification for straining water for food (dental filtration)

  • Both teeth and baleen at the same time

    • Baleen inside of gums and teeth on outside of gums. Have both options when eating.

    • Loose teeth later on

    • Had blood vessels in their gums that match up with the blood vessels that supply blood vessels of toothed whales

  • Teeth w/ additional groves

    • other structure that doesn’t fossilize (baleen don’t fossilized)

  • Lost teeth - had only gums - developed baleen to compensate

Family Aetiocetidae: Early Odontocetes

  • Asymmetrical cranium

    • melon developed over time. They start w/ symmetrical

    • depression in the skull that eludes to a small melon present

  • Moderated degree of telescoping

  • Heterodeont dentition

4 main challenges had to be overcome to evolve form terrestrial to aquatic

  • Swimming (hydrodynamics and buoyancy)

  • Diving Physiology

    • Drag and friction asscoated with a denser medium.

  • Thermoregulation (heat loss vs overheating)

    • Water is more conductive in water than air. Loss of heat quicker in water

    • Have to breath air, diving down at depth they have to store that air; deal w/ pressure changes

  • Osmoregulation (water and electrolyte balance)

    • Control changes b/w water and electrolytes


Swimming Adaptation

  • Nostrils

    • muscle control in nose to open/close; also prevents cold water from entering; raising head vs skimming the surface

  • Forelimbs – large SA

    • aid mobility in water (ie paddle) = greater surface of force against the water; steering if not used to propel the animal (whales, manatees)

  • Hindlimbs

    • loss of # pf appendages and increase in SA

Locomotion Cetacean and Sirenian

  • Dorso- ventral undulation of axial skeleton

  • Mammals skeleton moves up and down

    • Increased vertebrae

    • More flexible = reduced zygapophyses

      • Pos: Greater momentum and flexibility

      • Neg: lose strength (no strong support structure); if they end up on land (stranded) they will crush themselves with the weight of their body – spine is not strong enough to hold up body weight

    • Stabel vertebrae have connection b/w adjacent vertebrae (zygapophyses)

      Strength and ability to hold body upright

Swimming: Hydrodynamics

  • Aquatic medium (water)

  • >800 water denser than air

Drag solution

  • Streamline body reduces drag and friction

  • A large body reduces drag and friction

    • SA: volume ratio

    • Less SA reduces drag

Body shape of mammal swimmers

  • Fewer contours

  • Rounded edges that taper progressively as you move toward the tail

Measuring streamlining

  • Head to tail/hind limbs = body length

  • Body length = chord

    • They are the same term

  • Fr: 3-7 = optimal range of fully aquatic animal

  • Dash line is the ideal FR = 4.5

    • Reduces drag to the ma amt. for that body size

Blubber and Streamlining

  • smooths out body contours

  • Extremely smooth skin = reduces rejection and reduces drag

    • Shed epidermis every 2 hours (dolphins)

    • Cetaceasn have reduced hair or no hair

  • Dotted line = blubber

  • White = muscle

  • Blubber (vs fat)

    • More defined layer

    • Fat is in irregular shapes

  • Structure is maintained (clearly defined layer) via collagen network

  • Attached to muscle layer

    • Fat is a free floater

  • Vascularized - blood vessels

Swimming: Buoyancy

  • Upward force keeps animal afloat (reduces rate of decent)

    • influences

      • Blubber

      • Fat-filled bones (many Cetaceans)

      • Ventral bones more dense than dorsal bones (Sirenians)

  • Modified forelimbs

    • lift

  • Lung and other air-filled sinuses in the head region

    • close to swim bladder (compression/collapse for dive)