MAR 370: Exam 1 Review

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Characteristics of Mammals
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Morphological Adaptations of Mysticetes (Baleen Whales)-Baleen -Greatly enlarged buccal cavity (beginning of the alimentary canal, which leads from the pharynx to the oesophagus) -Mandibles joined by flexible ligament -Cavum ventrale (intramuscular space located between the bottom of the tongue and the walls of the buccal cavity, which extends all the way down to the whale's belly button) -Throat grooves (rorquals)Foraging Behavior of Mysticetes (Baleen Whales)-Skimmers: 1 step e.g. Right whales feed by swimming with their mouths open using ram filtration -Gulpers: 2 steps e.g. Humpback whales engulf dense patches of prey -Sifters: 2 steps e.g. Gray whales sift demersal preyTaxonomy of PinnipedsOrder: Carnivora 1. Sub-Order Pinnipedia -Family Otariidae - Fur Seals & Sea Lions -Family Phocidae - True Seals -Family Odobenidae - Walrus 2. Sub-Order Fissipedia -Family Mustelidae - OttersMorphology of Pinnipeds-Streamlined Body Shape - Blubber & Fur -Hind Flippers -Homodont Cheek TeethWhat is unique about the crabeater seal and leopard seal's teeth?Designed to catch krill in the grooves of the teethMorphology of Extant PinnipedsWhat is unique about pinnipeds compared to other marine mammals?Tied to land for breedingMorphology of Marine Otters-Streamlined Body Shape - Fur -Short Legs and Webbed Feet -Extremely Dense Fur Coats -Heterodont DentitionScientific name for sea otterEnhydra lutrisScientific name for marine otterLontra felinaMorphology of Sirenians-Streamlined Body Shape - Blubber -No External Pinnae or Pelvic Limbs -Intra-abdominal Testes -Dorso-ventrally flattened Tail Fluke -Axillary Mammary Glands -Very Sparse Hair -Pachyostotic BonesOrder Sirenia-Manatees -Dugongs -Steller's Sea Cow [EXTINCT]Whale Diversity~ 90 different species Mysticetes: 14 species Odontocetes: ~76 speciesWhat whales are found in NY?Mysticetes: -Blue -Fin -Sei -Humpback -Minke -N. Atlantic Right Odontocetes: -Sperm -Dolphins -Porpoises + many other odontocetesScientific name for humpback whaleMegaptera novaeangliaeScientific name for minke whaleBalaenoptera acutorostrataScientific name for fin whaleBalaenoptera physalusScientific name for right whaleEubalaena glacialisWhy are some whale populations so small?Historically --- hunting Currently --- ship strikes, gear entanglement, ecosystem degradation, bycatchWhy is it difficult to study whales?-Spend most (~ 95%+) of their time underwater -Can travel quickly (while out of sight) -Ocean is very big, relatively few animals in any area at one time -All marine mammals are protected (federal law) so permits are needed for any study -Different methods are required for different questions and speciesChallenges of ocean living-Highly conductive, cold environment (Water is 25x more conductive to heat than air) -Marine mammals are endothermic animals -Keeping warm is a priority!HomeothermyMaintenance of constant body temperature, usually warmer than that of the environmentEndothermyUse of elevated metabolism to maintain homeothermyEctothermyReliance on external sources of heat (solar radiation, conduction of heat from warm surfaces) to maintain an elevated body temperaturePoikilothermyFailure to regulate body temperature; conformance to environmental temperatureBasal Metabolic Rate (BMR)The number of calories burned as the body performs basic (basal) life-sustaining functionsThermoneutral ZoneRange of ambient temperatures where the body can maintain its core temperature solely through regulating dry heat lossSources of heat loss-Conductance -Convection -Radiation -EvaporationHeat loss formulaH = SA · C (Tb - Ta) H = Conductive Heat Loss SA = Surface Area C = Thermal Conductance Tb = Body Temperature Ta = Ambient TemperatureMeans of reducing heat loss-Large Body Size -Reduction in Surface Area to Volume Ratio -Decreased Thermal ConductanceSurface Area to Volume RatioThe greater the surface area, the greater the potential heat gain or loss through it. *a small S/V ratio implies minimum heat gain and heat lossBergmann's ruleWithin a broadly distributed taxonomic clade: -Populations and species show larger body sizes closer to the poles (colder environments) -Away from the poles (warmer environments) = smaller body size Why? Larger animals have a lower SA: V, reduced heat lossPilot whales and Bergmann's ruleLong-finned pilot whales (more northern species) are larger and have lower SA:V than short-finned pilot whales *Fits Bergmann's ruleHow do marine mammals reduce their thermal conductance?Sea Otters & Fur Seals: -Dense fur traps air -Dense under hairs -Sebaceous glands -Squalene (sea otter)Blubber-Lipid-rich hypodermis of marine mammals -Found directly under the skin -Highly modified form of adipose tissue "Blubber is a pliant biocomposite formed by adipocytes and structural fibers composed of collagen and elastic fibers."Functions of blubber-Insulates -Adjusts buoyancy -Defines body shape and streamlines -Serves as an energy depot -Acts as a biological springWhat affects insulative properties of blubber?-Thickness -Lipid content -Blood flowWhat is a better conductor of heat: dry fur or blubber?Dry furStratification of blubberOuter Layer: Structural and thermoregulatory Inner Layer: Metabolically activeRegional heterothermyThe ability to control body temperature in at least one region of the body and to control this in isolation from other regions -Thermal windows (thinly insulated flippers and fins) -Differential blood flow -Counter-current heat exchangersCounter-current heat exchangersThe crossover of heat between two flowing bodies flowing in opposite directions to each otherReproduction thermoregulationPhocids, Sirenians & Cetaceans have cryptic testes but mammalian sperm production is optimized several degrees below core temperatures -Testes of dolphins are exposed to the intense thermogenic effects of hypaxial locomotor musclesAllen's ruleThe limbs, ears, and other appendages of endothermic animals living in cold climates tend to be shorter than animals living in warm climates Why? Longer appendages dissipate heatPilot whales and Allen's ruleLong-finned pilot whales (more northern species) have larger appendages than short-finned pilot whales *Does NOT fit Allen's rule Why? -Highly insulated bodies of large long-finned pilot whales require mechanisms for rapidly dissipating heat after bouts of exercise - thermal windows -In marine mammals, blood flow can be altered within appendages to conserve or dissipate heatChallenges for locomotion in water-Density of water is almost 1000 times greater than air -Viscosity of water is 60 times greater than air so -The forces of drag are much greater in waterDragThe rate of removal of momentum from a moving body immersed in a fluidP ∝ DuThe power (energy) required to swim is proportional to drag and velocity P = power output D = drag u = speedTypes of dragViscous Drag or Skin Friction: -Effects felt in boundary layer (close to body surface) -Occurs due to the friction of the fluid against the body surface (boundary layer) -Proportional to surface area and the square of speed Pressure Drag: -Occurs due to the distribution of pressure around a body, effects on fluid flow -Body creates a low-pressure wake behind it -Proportional to surface area and the square of speed Wave Drag: -Experienced in near-surface waters -Kinetic energy transformed into potential energy in waves -Energy used in producing waves rather than moving forward -Wave drag 4-5 times higher near surface -Reaches a maximum at a depth of 0.5 body diameter -Negligible at depths > 3 body widthsWhat is unique about the surface areas of marine mammals?On average, the surface area of a marine mammal is 23% less than that of a terrestrial mammal of similar massHow do sea otters and pinnipeds maintain smooth skin?-Position and morphology of guard hairs -Point caudally, flattened -Form a smooth surface when wetHow do cetaceans maintain smooth skin?High turnover rate of epidermal cellsIntegumentThe integumentary system includes the epidermis, dermis, hypodermis, associated glands, hair, and nails Functions: -Thermoregulation -Drag reduction -Buoyancy controlBlubber & buoyancyBlubber is less dense than waterFineness Ratio (FR)Ratio of the length of a body to its maximum width (Chord Length / Maximum Thickness) -Shapes that are short and wide have a low fineness ratio -Shapes that are long and narrow have a high fineness ratioCosts of lunge feeding in larger rorquals-Larger rorquals don't have increased diving capacity in spite of their larger size -Larger rorquals can take bigger gulps, but with an energetic cost because of increased dragReynolds NumberDimensionless number that describes importance of drag in fluid flow R = (Body Length x Swimming Velocity) / (Water Viscosity / Water Density) Viscosity and Density are relatively constant, so Reynolds numbers are influenced primarily by size and velocity -Low Reynolds numbers: Skin friction is important -High Reynolds numbers: Pressure drag dominatesReducing drag through morphology-Reduced surface area -Smooth body surface -Smooth integument (loss or modification of hair) -Streamlining -Sculpting through blubber deposition -Reducing the size of external appendagesIncreasing efficiency through behavior-Reducing Wave Drag -Swimming away from the surface while submerged -Leaping when surfacing at speed (porpoising) -Hitching a Ride - Drafting -Wave riding -Calves drafting in infant position -Gliding While DivingEvolution of locomotion in marine mammals-Semi-aquatic mammals use primitive forms of locomotion, such as paddling -Cetaceans, pinnipeds and sirenians use a more efficient, lift-based system of propulsionModes of locomotion in marine mammalsPinnipeds: Appendicular musculoskeletal system -Otariids: forelimb propulsion -Phocids and Odobenids: lateral hindlimb propulsion Cetaceans and Sirenians: -Axial musculoskeletal system -Alternating contraction of epaxial and hypaxial muscles (epaxial muscles - upstroke; hypaxial muscles - downstroke) -Thrust from flukesConnective tissue sheath-Anchor point for muscles/tendons -Resists torsion -Maintains shapeMaximum diving capacities of marine vertebratesHumans: 253 m / 6 min 41 secs Emperor Penguins: 535 m / > 20 minutes Weddell Seals: 700 m / 82 minutes Elephant Seals: 1,503 m / 67 minutes Sperm Whales: 2,035 m / 73 minutes Cuvier's beaked whales: 2992 m / 138 minutesProblems faced by mammalian divers-Hydrostatic pressure -Oxygen conservationPhysics of pressure-Pressure increases by one atmosphere every 10 meters Boyle's Law: Pressure * Volume = Constant -Thus, at 10 m the volume of a gas will be 1/2 of that at the surfaceHenry's LawThe amount of dissolved gas in a liquid is proportional to the partial pressure above the liquidHow do deep diving marine mammals overcome Henry's Law?Exhale during the entire ascentThe Bends-Decompression sickness -Occurs when dissolved gases (particularly N2) come out of solution and form bubbles inside the body during decompression (typically on ascent) -Many symptoms depend on where bubbles are formed or where bubbles migrateSCUBA divers are taught to:Never hold your breath while ascendingWhy don't marine mammals get the bends?-Isolate N2 from site of gas exchange -Collapse of thoracic cavities -Alveolar collapse -Exhale before diving (phocids) -Armored terminal airways *present in ALL marine mammalsAdaptations for O2 conservation during apnea-Increased oxygen storage capacity -Bradycardia (slow down heart rate) -Peripheral VasoconstrictionProblem with conserving oxygenMore oxygen = more CO2 + lactic acidOxygen storage capacities of marine mammals in blood and lungsDeep Divers (ex: Weddell Seal): Predominantly blood oxygen storage Intermediate Divers (ex: Bottlenose Dolphin): Roughly equal blood and lung oxygen storage Shallow Divers (ex: Sea Otter): Predominantly lung oxygen storageHow is oxygen storage enhanced in deep diving mammals?-Blood volume -Number of red blood cells -Hemoglobin and myoglobin concentrationsTerminology of diving physiologyHypoxia = decline of available O2 Hypercapnia = increase in CO2 Asphyxia = hypoxia plus hypercapnia Acidosis = accumulation of lactic acid Ischemia = tissues deprived of circulating bloodScholander Diving ResponseFor marine mammals making forced dives: -Cessation of breathing -Pronounced bradycardia -Reduced distribution of cardiac output -Selective ischemia through regional vasoconstriction -Maintenance of blood flow to vital organs -Anaerobic metabolism after O2 supplies depleted -Accumulation of products of anaerobic metabolismHistory of studying diving in marine mammals1. Restrained animals in laboratory 2. Free diving captive animals 3. Free-diving Weddell seals 4. Time-depth recorders (TDRs) 5. Real-time physiological monitoringWhat did scientists learn while monitoring blue whale heart rates?Whales slow their heart rates down considerably as they dive to eat krill *way to conserve oxygen so it can stay underwater longer before surfacing to breatheAerobic Dive Limit (ADL)Maximum breath-hold without an increase in blood lactic acid concentration during or after the dive Depends on: -Stored oxygen reserves -Oxygen consumption rate -Degree of peripheral vasoconstriction -Rate of lactic acid production & consumptionBeaked whales can dive to depths of nearly 3000 m, which is deeper than sperm whales. How can the comparatively small beaked whales undertake such extreme dives?-Dives for most marine mammals are typically within ADL -In some extreme deep diving species, dives regularly exceed ADL but -Blood lactate levels do not indicate anaerobic metabolismBenefits of Gliding/Sinking vs. Actively Swimming-Negative buoyancy allows for gliding -Less energy and oxygen consumed during glidingWhat have deep divers evolved to have more of?Inexpensive tissues -Extreme divers invest less (show a smaller percentage of body mass) in expensive tissues- i.e., a larger percent of their body mass is made up of integument, bone and muscleCharacterizing marine mammal diets1. Direct observation 2. Reconstructing digested prey remains: -Stomach contents -Scats 3. Chemical composition of tissues: -Fatty acids -Stable isotopesProblems with direct observationBiased towards: -Near-surface prey capture -Protracted capture events -Large prey *Only reliable with ottersProblems with digested remainsBiased towards: -Harder-to-digest material -Otoliths -Squid beaks *Usually performed on dead animals as it is difficult to do with live animalsProblems with chemical compositionFatty Acid Analysis: cannot give exact numbers but can give percentages Stable Isotope Analysis: depends on the turnover rate of consumed tissues (ex: baleen plates have no turnover, bones take years for turnover, red blood cells take months to turnover, liver cells take weeks to turnover)Phylogeny & Feeding EcologyPinnipeds: graspers (single prey) / suckers Sirenians: grazers (plants) Otters: graspers (single prey) Mysticetes: strainers (multiple prey) Odontocetes: graspers (single prey)Foraging behavior of mysticetesSkimmers: 1 step e.g. Right whales Gulpers: 2 steps e.g. Balaenopterids Sifters: 2 steps e.g. Gray whale *Humpback bubblenet feeding: example of cooperative foragingForaging behavior of ottersMainly consume crustaceans, bivalves, urchins, snails *Maternal transmission of foraging specializationForaging behavior of odontocetesCooperative foraging is prevalent Bottlenose Dolphins: -Strand feeding -Fish-whacking -Kerplunking -Crater feeding -Begging Spinner Dolphins: -Cooperative prey herdingLaw of diminishing returnsin productive processes, increasing a factor of production by one unit, while holding all other production factors constant, will at some point return a lower unit of output per incremental unit of input