Simone Baumann-Pickering May 9, 2013 …cetus.ucsd.edu/SIO133/PDF/Diving Physiology Osmoregulation...
Transcript of Simone Baumann-Pickering May 9, 2013 …cetus.ucsd.edu/SIO133/PDF/Diving Physiology Osmoregulation...
DIVING PHYSIOLOGY, OSMOREGULATION & HEALTH
Simone Baumann-Pickering May 9, 2013 [email protected] (858) 534-7280
Marine Mammal Biology
LITERATURE
• Perrin WF, Wuersig B, Thewissen JGM (2009) Encyclopedia of Marine Mammals, 2nd ed, Academic Press * Diving Physiology * Diving Behavior * Osmoregulation
• Berta A, Sumich JL, Kovacs KM (2006) Marine Mammals: Evolutionary Biology, 2nd ed, Academic Press * Chapter 10
REASONS FOR DIVING
• Forage for food • Increase swimming efficiency (low drag) • Save energy (low metabolic costs) • Sleep while minimizing risk of predation
• Human dive record: * Dynamic Apnea 273 m * Static Apnea 11 min 35 sec
DIVING PHYSIOLOGY
NEW MAMMALIAN DIVE RECORD August 6, 2010, NW of San Clemente, nearby ship using mid-frequency active sonar • Cuvier’s beaked whale * 3000 m depth * 137 minutes * Followed by 7 hours of shallow dives
DEEP / PROLONGED DIVES
• Conflicting, physiological conditions during apneic conditions * Oxygen stores deplete * CO2 and lactate increase in blood and muscle tissue (acidic blood
serum and cell fluid)
• Period of hypoxia: muscle activity maintained anaerobically (low efficiency) * Anaerobic glycolysis + creatine phosphate catabolism * Greater accumulation of lactate – longer subsequent recovery
• Large brains in marine mammals * human brain has permanent damage when oxygen supply is
interrupted for >3 min
DEEP / PROLONGED DIVES
• Increase in water pressure (1 atm for each 10 m) * Compression of air-filled spaces -> distortion or
collapse * Absorption of gases from air at high pressure
• Toxicity of oxygen at high concentrations • Narcotic effect of nitrogen on central nervous system • Damaging bubbles in tissues and blood during ascent
* Sensitivity of nervous system to high pressure • Terrestrial animals: over stimulation, uncoordinated nerve
conduction and dysfunction
ADAPTATIONS
• Cold, dark water • High pressure environment • Rich food sources
• Adaptations * External body shape * Internal structures * Sensory system
OXYGEN STORES
• Storage in 3 compartments * Respiratory system
• Lung volume • Concentration of oxygen in lung at start of breath hold
* Blood • Blood volume • Concentration of oxygen binding protein - hemoglobin
* Body musculature • Muscle mass • Concentration of oxygen binding protein – myoglobin
* MYOGLOBIN – most characteristic for deep divers!
OXYGEN STORES / DISTRIBUTION
• Increased blood volume (2-3 x 70 ml/kg human value) -> increased blood oxygen stores
• Greater blood volume in more active, and longer diving species
• Largest blood volumes (200-260 ml/kg) in some of best divers: elephant seals, Weddell seals, sperm whales
OXYGEN STORE
• Humans: 20 ml O2/kg body mass • Elephant seal: 100 ml 02/kg body mass * (human comparison) * 3x blood volume * 1.5x hemoglobin concentration * 10x myoglobin concentration -> most of its oxygen in blood and muscles (exhale before diving; lung collapsed during dive)
OXYGEN STORES / ADAPTATIONS
• Pinnipeds: ascending aorta with increased diameter (30-40%) -> aortic bulb (aortic arch) * Size of the bulb correlated to diving habits
• Cetaceans: some species bulbous expansion of aortic arch * Mechanical properties of walls (thickness,
organization of elastic tissues)
RETIA MIRABILIA (WONDERFUL NETS)
• Extensive contorted spirals of blood vessels (mainly arteries but with thin-walled veins)
• Inner dorsal wall of thoracic cavity, extremities or periphery of body
• Sperm whale: most extensive
• Blood reservoirs to increase oxygen stores
CARDIOVASCULAR RESPONSE
• 2 categories of dives * Routine duration * Extended dive
• Measurements of cardiovascular and metabolic response are limited, most measurements from seals
• Arrhythmic breathers, pauses between series of breaths * Resting maintenance heart rate = respiratory pause or
apnea * Heart rates during dive are lower than rate of resting
apneusis * Heart rate even lower during extended dive
CARDIOVASCULAR RESPONSE
• Gastric, renal, hepatic functions reduced; 50% of resting metabolism
(extrapolation from indirect measures) • Muscle (probably) relies on internal store of oxygen
bound to myoglobin for aerobic metabolic needs • Extended dives (3-5 x routine dives) uncommon
* Urgent need (e.g search for new hole under ice; escape from predator)
* Limitation of blood flow to obligate aerobic tissue (e.g. brain), additionally • Slow heart rate • Lowest blood flow to muscle (myoglobin, glycogen)
AEROBIC DIVING LIMIT
• Lactate accumulates in muscle as muscle oxygen is depleted
• After surfacing: increased blood flow to muscle, lactate is flushed into circulation, disappears over several minutes
• Aerobic Diving Limit (ADL): diving duration beyond which there is net increase in lactate production
• Calculated ADL (cADL): O2 store / metabolic rate * Prediction of basic information about foraging * Clarification of physiological responses * Models to breath holding (e.g. elephant seal exceeds
cADL, how?)
BLOOD LACTATE – WEDDELL SEAL
Red: no net production of lactate Blue: net production
Inflection: Aerobic Diving Limit (ADL) or Diving Lactate Threshold (DLT)
ADAPTATIONS TO PRESSURE
• Increase in water pressure (1 atm for each 10 m) * Compression of air-filled spaces -> distortion or
collapse * Absorption of gases from air at high pressure
• Toxicity of oxygen at high concentrations • Narcotic effect of nitrogen on central nervous system • Damaging bubbles in tissues and blood during ascent
* Sensitivity of nervous system to high pressure • Terrestrial animals: over stimulation, uncoordinated nerve
conduction and dysfunction
ADAPTATIONS TO PRESSURE
• 3 major airspaces within most mammals * Facial sinuses absent in marine mammals * Middle ear – rigid structure, no compressibility
• Complex vascular sinus lining of the wall • Blood sinus volume increases as pressure reduces gas
volume -> close match between ambient and blood pressure, transferred from one fluid to another (hydraulic compression)
* Lung (largest airspace) – modifications that make alveoli collapse first, squeeze gases into upper airway spaces • Gas exchange ceases in upper airway spaces (important for O2
and N2 partial pressure in blood)
BREATHING
• Breathing cycle * Rapid exhalation (blow) * Slightly longer inhalation
• Extremely high flow rates over breathing cycle * Flexible chest walls * Cartilage reinforcement of
smallest terminal air passages (prevent collapse)
• 0.1 s for dolphins; 2 s for blue whales (1500 l)
Flow rate breathing grey whale calf
BREATHING
• Inspiration: extensive elastic tissue in lungs and diaphragm stretched by diaphragm and intercostal musculature
• Expiration: fibers recoil rapidly -> nearly completely empty lungs
• Rapid uptake of oxygen, ~90% per breath (humans, terrestrial mammals: 20 %)
• Lung collapse ~(25) 50-100 m
OSMOREGULATION – SEAWATER
• No freshwater • Different electrolyte concentrations * Seawater (1000 mOsm L-1) * Body water (300 mOsm L-1)
• Prey * Hypotonic (fish) with seawater * Isotonic/hypertonic (invertebrates)
DRINKING SEAWATER
• Must be able to concentrate urine
Dolphin: gains water from drinking seawater Human: loss in water
OSMOREGULATION
• Preformed water * Food: 60-80% water content * Seawater
• Metabolism 6O2 + C6H12O6 = 6H20 + 6CO2
* 1g Fat = 1.07 g H20 * 1g Protein = 0.56 g H20 * 1g Carbohydrate = 0.39 g H20
OSMOREGULATION
• Larger kidneys in marine mammals • High concentrating ability * Mysticetes -> hypertonic invertebrate prey ->
thousands of kidney lobes * Odontocetes -> hypotonic prey ->
hundreds of kidney lobes
ADAPTATIONS TO LIFE AT SEA
• Taxonomically distant groups evolved similar biological mechanisms to cope with marine existence * Biological and behavioral strategies for controlling • Body temperature • Diving • Maintaining salt and water balance • Promoting reproductive success
• Adaptations vital to health and survival
POSSIBLE PROBLEMS
• Impairment in one body system can disturb equilibrium -> secondary problems threating health * E.g. blubber: hydrodynamic shield + source of energy,
insulation, water reserves, buoyancy * Food scarce -> blubber depletion
• Less able to rest at surface, maintain body heat, forage, escape predators, keep up with group -> stress
• Possible disease, further weakening • Stress poorly understood * Can disrupt thyroid + adrenal gland function, water and
electrolyte balance, metabolism, reproduction, weaken immune response
HEALTH RISKS
• Reproductive failure/death of newborn • Starvation • Direct environmental effects • Trauma • Predation • Parasites • Microorganisms • Metabolic disorders • Tumors • Biotoxins • Strandings • Habitat alteration and disturbance
REPRODUCTIVE FAILURE/NEWBORN DEATH
• Weakness or disruption at any point can lead to failure – abortion, stillbirth, premature birth, weakness or death of newborn
• Health and nutritional condition of mother affects the fetus * Environmental disruption * Epidemic disease * Reduced prey stocks * High levels of anthropogenic contaminants
STARVATION
• Starvation when food is plentiful: dependent young, sick, old
• Survival duration without food dependent on: * Age, fat reserves, metabolic rate, energy demands, general
health * Baleen whales: feed little over 6-8 months * Sea otters: 2 days (can die from complications)
• Major cause for death in pinniped and sea otter pups * Dependency on health of mother and food supply * Newly independent juvenile sea otters: high need for food,
inexperience of gathering • Starvation when food sources are low (overgrazing,
overfishing, climatic or oceanographic fluctuation)
DIRECT ENVIRONMENTAL EFFECTS
• Intensely cold winters (e.g. killed up to 2% of Florida manatee population, mostly juveniles)
• Storms hitting pinniped rookery during breeding -> hypothermic pups, injuries, drowning, etc.
• Unexpected frozen water surfaces: sea otters trapped outside; cetaceans trapped in ice
• Unseasonable warm weather: * fractured ice: crush breeding seals and pups * melting ice: walrus mothers abandon calves
TRAUMA
• Natural source of injury: storms, predators, aggressive encounters
• Anthropogentic source: fishery operations, shipping, (recreational) boating * Historically: whaling; today more accidents * Leading: interaction with fisheries • Direct during fishing activities • Indirect during entanglement of lost gear
* Vessel collisions * Noise impacts
PREDATION
• Easiest target: small, inexperienced animals, found in particular place on schedule
• Predators: Arctic fox, polar bears, killer whales, sharks
• Predation consequence on female may effect current pup and possible future pup (recovery period without pregnancy)
PARASITES
• Parasitic infestation unproblematic condition * Amphipods / copepods (eat whale skin) * Seal lice (small numbers, seal blood) * Gastrointestinal helminths
• Harmful for individual * Heartworm, lungworm, hookworm * Nematodes (mammary glands, cranial sinuses, kidneys) * Trematodes (Nasitrema spp.: cranial sinuses; Campula spp.:
liver and pancreas) * Wrong host for parasite (e.g. protozoan Toxoplasma gondi
from cat; may lead in sea otters to encephalitis, heart disease, abnormal behavior)
MICROORGANISMS
• Bacteria, fungi, viruses * Many organisms are considered normal * Few are pathogenic (= cause infectious disease),
some more threatening than others • Degree of infectious disease depends on * Aggressiveness of organism * Susceptibility of host (condition of immune system) * Age of individual (very young or old more likely to
get infected)
BIOTOXINS
• Thousands of species of marine phytoplankton * 40 can produce toxins harmful to top predators
• Examples * Ciguatoxin: (dinoflagellate) 1978, 50 Hawaiian monk
seals -> emaciated, parasitic infections, died * Saxitoxin in mackerel (neurotoxin): 14 humpback
whales died from respiratory paralysis, Cape Cod 1987 * Brevetoxin (neurotoxin in dinoflagellate Karenia brevis
(red tide)): danger to bottlenose dolphin, manatees (Florida, Gulf of Mexico)
* Domoic acid (neurotoxin in diatom Pseudonitzschia sp): CA sea lions along central California -> convulsions, loss of coordination, vomiting