Simone Baumann-Pickering May 7, 2013 sbaumann@ucsd.edu (858) 534-7280 Marine Mammal Biology SIO 133 LOCOMOTION, ENERGETICS & THERMOREGULATION
HYPERPHALANGY (POLY/)HYPERDACTILY A) Risso s dolphin B) Killer whale
LITERATURE Perrin WF, Wuersig B, Thewissen JGM (2009) Encyclopedia of Marine Mammals, 2 nd ed, Academic Press * Swimming (Hydrodynamics) * Energetics Berta A, Sumich JL, Kovacs KM (2006) Marine Mammals: Evolutionary Biology, 2 nd ed, Academic Press * Chapter 8 + 9
LOCOMOTION (ANATOMY) Appendicular skeleton: * Pectoral Limb Complex (Forelimb) * Pelvic Limb Complex (Hindlimb) Terrestrial locomotion Swimming * Mechanics * Hydrodynamics * Energetics
PECTORAL LIMB COMPLEX
FORELIMBS
PELVIC LIMB COMPLEX
CETACEAN TAIL (FLUKE)
CETACEAN DORSAL FIN
TERRESTRIAL LOCOMOTION - OTARIIDAE a) New Zealand sea lion b) New Zealand fur seal
TERRESTRIAL LOCOMOTION - PHOCIDAE
TERRESTRIAL LOCOMOTION - WALRUS
MORPHOLOGY - STREAMLINING Body shape of mammalian swimmers (a-g) and semiaquatic mammals (h-l)
MORPHOLOGY - PROPULSION Increased surface area over evolutionary time Inter-digital webbing, to fins, to large flukes
SWIMMING MECHANICS A) Polar bear Forelimb crawl B) Sea otter Pelvic paddle Sea Otter C) Eared seals Foreflipper locomotion Thunniform Propulsion from posterior 1/2 to 1/3 of body D) True seals Lateral = side-to-side E) Cetaceans & Sirenians Dorso-ventral = up-down Otariids
SWIMMING MECHANICS Propel-recover stroke cycle to propulsion over entire stroke cycle Dog paddling ½ propulsion, ½ recovery Fluking Down and upswing of flukes provide equal propulsive force
BEHAVIORAL ADAPTATIONS 22 mph 9 mph
HYDRODYNAMICS - DRAG Properties of Water Affect Locomotion Mammals neutrally buoyant in water Resistance in water > air * 800x denser * 30x more viscous Drag increases with velocity * Total Drag = 1 / 2ρV 2 ACd ρ = Density of fluid V = velocity of the fluid relative to the body A = characteristic area of the body Cd = drag coefficient
HYDRODYNAMICS Drag effected by * Skin friction * Pressure drag by surrounding fluid * Wave drag on/ near water surface * Induced drag (water deflection) Example: Sea otter Surface Submerged (Data from Williams 1989)
HUMPBACK WHALE FLIPPER
ENERGETICS ENERGY FLOW
RESTING METABOLIC RATE
ENERGETICS SWIMMING (HUMAN)
ENERGETICS SWIMMING (DOLPHIN) Optimal range of speed 2.7 m/s 9 mph (Data from Yazdi et al. 1999)
ENERGETICS Effect of body size on cost of transportation
ENERGETICS Cost of Transportation (COT) = Metabolic rate (Oxygen consumption) Swimming speed Why is it higher? Cost of Endothermy Cost of higher metabolic rates when resting
ENERGETICS
LOCOMOTION AND ADAPTATIONS Decrease cost of swimming Decrease oxygen consumption Make swimming more efficient * Morphological changes in body shape and propulsive surface area * Mechanical changes in swim stroke * Behavioral tricks
BEHAVIORAL ADAPTATIONS Porpoising at high speeds * Have to surface to breathe * Cost due to wave drag * Less drag in air than in water (less dense)
THERMOREGULATION
THERMOREGULATION = process of regulating body temperature Poikilotherm * Temperature conformer: T b T a Homeotherm * Temperature regulator: T b constant Endotherm * Endogenous heat production to maintain T b Ectotherm * External source of heat production to maintain T b
THERMOREGULATION CHALLENGES Marine environment generally much colder than T b Water conducts heat ~25x faster than air Amphibious marine mammals (e.g. pinnipeds) must thermoregulate in air & water
THERMOREGULATION BALANCE Heat loss = Heat production Metabolism: Food + O 2 = Heat + H 2 0 + CO 2
THERMOREGULATION BALANCE Heat loss = Heat production Convection = heat transfer to a fluid Conduction = heat transfer to a solid Radiation = transfer of radiant energy Evaporation = heat transfer by changing water from liquid to gas (respiratory water loss)
THERMOREGULATION STRATEGIES Lower temperature differential lower T b * Typical mammalian T b = 36-38 C * Cetacean T b = 35.5 C Increase body size * Decrease surface area to volume ratio Increase metabolism * Increase heat production Increase insulation lower conductance * Blubber * Density / length of hair Vascular control * Counter-current heat exchange
COUNTER-CURRENT HEAT EXCHANGER
DOLPHIN HEAT EXCHANGE
SPERMATIC ARTERIAL PLEXUS
THERMOREGULATION STRATEGIES Lower temperature differential lower T b * Typical mammalian T b = 36-38 C * Cetacean T b = 35.5 C Increase body size * Decrease surface area to volume ratio Increase metabolism * Increase heat production Increase insulation lower conductance * Blubber * Density / length of hair Vascular control * Counter-current heat exchange Behavioral thermoregulation * Clump together when cool or to save heat