DIVING PHYSIOLOGY, OSMOREGULATION & HEALTH

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1 Simone Baumann-Pickering May 9, 2013 (858) Marine Mammal Biology DIVING PHYSIOLOGY, OSMOREGULATION & HEALTH

2 LITERATURE Perrin WF, Wuersig B, Thewissen JGM (2009) Encyclopedia of Marine Mammals, 2 nd ed, Academic Press * Diving Physiology * Diving Behavior * Osmoregulation Berta A, Sumich JL, Kovacs KM (2006) Marine Mammals: Evolutionary Biology, 2 nd ed, Academic Press * Chapter 10

3 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

4 DIVING PHYSIOLOGY DURATION 30 min 2 min

5 DIVING PHYSIOLOGY DEPTH

6 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

7 DEEP / PROLONGED DIVES Conflicting, physiological conditions during apneic conditions * Oxygen stores deplete * CO 2 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

8 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

9 ADAPTATIONS Cold, dark water High pressure environment Rich food sources Adaptations * External body shape * Internal structures * Sensory system

10 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!

11 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 ( ml/kg) in some of best divers: elephant seals, Weddell seals, sperm whales

12 BLOOD VOLUME

13 OXYGEN STORE Humans: 20 ml O 2 /kg body mass Elephant seal: 100 ml 0 2 /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)

14 OXYGEN STORES / DISTRIBUTION L = Lung; B = Blood; M = Muscle

15 OXYGEN STORES / DISTRIBUTION

16 MECHANISM OF THE HEART

17 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)

dorsal wall of thoracic cavity, extremities or periphery of body

18 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

19 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

20 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)

21 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): O 2 store / metabolic rate * Prediction of basic information about foraging * Clarification of physiological responses * Models to breath holding (e.g. elephant seal exceeds cadl, how?)

22 BLOOD LACTATE WEDDELL SEAL Red: no net production of lactate Blue: net production Inflection: Aerobic Diving Limit (ADL) or Diving Lactate Threshold (DLT)

23 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

24 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 O 2 and N 2 partial pressure in blood)

25 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

26 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) m

27 OSMOREGULATION

28 OSMOREGULATION MAJOR FLUXES Goal: maintain homeostasis

29 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)

31 OSMOREGULATION SALT GLANDS

32 DRINKING SEAWATER Must be able to concentrate urine Dolphin: gains water from drinking seawater Human: loss in water

33 OSMOREGULATION WATER

34 OSMOREGULATION Preformed water * Food: 60-80% water content * Seawater Metabolism 6O 2 + C 6 H 12 O 6 = 6H CO 2 * 1g Fat = 1.07 g H 2 0 * 1g Protein = 0.56 g H 2 0 * 1g Carbohydrate = 0.39 g H 2 0

35 OSMOREGULATION ELECTROLYTES

36 OSMOREGULATION KIDNEY STRUCTURE

37 OSMOREGULATION KIDNEY STRUCTURE

38 OSMOREGULATION KIDNEY STRUCTURE

39 OSMOREGULATION Larger kidneys in marine mammals High concentrating ability * Mysticetes -> hypertonic invertebrate prey -> thousands of kidney lobes * Odontocetes -> hypotonic prey -> hundreds of kidney lobes

40 HEALTH

41 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

42 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

43 HEALTH RISKS Reproductive failure/death of newborn Starvation Direct environmental effects Trauma Predation Parasites Microorganisms Metabolic disorders Tumors Biotoxins Strandings Habitat alteration and disturbance

44 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

45 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)

46 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

47 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

48 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)

49 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)

50 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)

51 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

52 OTHER Strandings Habitat alteration and disturbance * Contaminants * Oil spills * Ingesting debris * Prey depletion * Nutrient enrichment (toxic algal blooms) * Anthropogenic noise

DIVING PHYSIOLOGY & OSMOREGULATION

Simone Baumann-Pickering May 13, 2015 sbaumann@ucsd.edu (858) 534-7280 Marine Mammal Biology DIVING PHYSIOLOGY & OSMOREGULATION LITERATURE Perrin WF, Wuersig B, Thewissen JGM (2009) Encyclopedia of Marine