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Marine Mammal Locomotion: Adaptations and Mechanisms

This article explores the locomotion methods of marine mammals, including pinnipeds, cetaceans, and sirenians. It discusses the various patterns of flipper and tail movement, as well as adaptations in the vertebral column and flukes. The evolution of locomotion in different marine mammal groups is also examined.

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Marine Mammal Locomotion: Adaptations and Mechanisms

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  1. Marine Mammal Locomotion MARE 390 Dr. Turner

  2. Locomotion Swimming by marine mammals is derived from: Paired flipper movements – pinnipeds & sea otters Vertical movement of caudal flukes – cetaceans & sirenians

  3. Pinniped Mechanics Terrestrial & aquatic locomotion achieved differently Aquatic - three distinct patterns: 1. Pectoral Oscillation – forelimb swimming used by otariids; flapping 2. Pelvic Oscillation – hindlimb swimming in phocids; alternating 3. Pelvic Oscillation (variant) – hindlimb swimming in odobenids; forelimbs also

  4. Movie Pectoral Oscillation Aquatic – flapping forelimbs, no hindlmbs

  5. Pectoral Oscillation Otariidae

  6. Pectoral Oscillation Otariidae

  7. Movie Pectoral Oscillation Terrestrial – posture (hind facing forward) allows for weight on all four limbs

  8. Pectoral Oscillation Otariidae

  9. Movie Pelvic Oscillation Aquatic – alternating hindlimbs, forelimbs for steering

  10. Movie Pelvic Oscillation Aquatic – alternating hindlimbs, forelimbs for steering

  11. Pelvic Oscillation Phocidae

  12. Pelvic Oscillation (Variant) Aquatic – hindlimbs used in alternating force; forelimbs either as rudders or paddles

  13. Pelvic Oscillation (Variant) Odobenidae

  14. Pelvic Oscillation (Variant) Terrestrial – hindlimbs can be rotated forward (like otariids) Belly supports more of body than limbs

  15. Pelvic Oscillation (Variant) Odobenidae

  16. Cetacean Locomotion Vertebral column – cervical, thoracic (rib attachments), lumbar regions (chevron bones)

  17. Cervical Vertebrae All cetaceans have 7 cervical (neck) vertebrae Different from other mammals – flat, fused Sperm whale – 6 fused Most others – 2+ fused Adaptation to high-speed swimming

  18. SCTS Subdermal Connective Tissue Sheath Collagenous sheath that restrains thoracic & lumbar vertebrae and gives rigidity to thorax & ↑ surface area for muscle connections of the back & tail

  19. Zygopophyses Anterior & posterior facing articular processes on vertebrae Work to link vertebrate together stiffens vertebral column Ligaments align vertebrae

  20. Flippers & Locomotion In cetaceans – forelimb proportions altered Pectoral fin is forearm & hand – elbow not external Also seen in marine reptiles, ichthyosaurs, mosasuars

  21. Pelvic Girdle & Locomotion Pelvic column reduced to innominate bones Portions of femus, tibia, or foot No direct connection to vertebral column

  22. Tail Fluke Locomotion Following basic components: 1. Cutaneous layer – like rest of body 2. Blubber layer – far thinner than rest 3. Ligamentous layer from caudal keels 4. Extremely dense fibrous material within ligamentous envelope

  23. Tail Fluke Shape The shape of the flukes differs among cetaceans in response to varying hydrodynamic parameters Trailing edges of most are slightly convex Other straight (Sperm whales) Curved (Humpbacks) Falcate (sickle-shaped; rorquals) Biconvex (narwhals)

  24. Dorsal Fin Shape Predominant in most cetaceans Supported by tough fibrous tissue – similar to flukes Provide additional surface for balance & maneuverability, thermoregulation, & conspecific recognition

  25. Movie Mechanics of Locomotion Modern cetaceans are caudal oscillators; swim by vertical movements of the flukes by alternate actions of epaxial & hypaxial muscles Similar to billfishes & tunas except plane

  26. Cetacean Locomotion Delphinidae

  27. Cetacean Locomotion Balaenopteridae

  28. Cetacean Locomotion Physeteridae

  29. Cetacean Locomotion Phocoenidae

  30. Cetacean Locomotion Monodontidae

  31. Cetacean Locomotion Iniidae

  32. Evolution of Cetacean Locomotion Evolved from an initial quadruped, pelvic phase, caudal undulation phase, & caudal oscillation

  33. Movie Movie Evolution of Sirenian Locomotion Caudal oscillation Poor swimmers compared to cetaceans Unable to reach sustained high speeds

  34. Evolution of Sirenian Locomotion Terrestrial quadrupeds – alternate thrusts of limbs Aquatic quadrupeds – dorsal ventral spinal undulation & thrusts of hind limbs Completely aquatic animals swimming with tail alone

  35. Sirenian Locomotion Trichechidae

  36. Sirenian Locomotion Dugongidae

  37. Movie Evolution of Mustelid Locomotion Hind limb much larger than forelimbs - terrestrial locomotion slow Walking & bounding

  38. Mustelid Locomotion

  39. Movie Evolution of Mustelid Locomotion Aquatic locomotion achieved by pelvic paddling (surface) & pelvic undulation (submerged)

  40. Mustelid Locomotion

  41. Movie Evolution of Ursid Locomotion Polar bears have few adaptations to the aquatic environment

  42. Ursid Locomotion

  43. Movie Evolution of Ursid Locomotion Swim with crawling motion – only use forelimbs; hindlimbs trail behind

  44. Ursid Locomotion

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