Adaptations to Aquatic Living (MARI 3090) - Fall 2023 PDF

Adaptations to Aquatic Living MARI 3090 – Marine Mammalogy, Dalhousie University Dr. Amanda Babin, Fall 2023 Why do we need to adapt? • To maximize our inclusive fitness • Measure of the ability for genetic material to propagate itself • Because other members of the population may share one’s gen...

Adaptations to Aquatic Living MARI 3090 – Marine Mammalogy, Dalhousie University Dr. Amanda Babin, Fall 2023 Why do we need to adapt? • To maximize our inclusive fitness • Measure of the ability for genetic material to propagate itself • Because other members of the population may share one’s genes, helping others may also propagate one’s genes • Depends on: • Individual’s ability to succeed • Rate of reproduction • Viability of offspring and kin Aquatic environment • Water 800 times denser than air • Water 60 times more viscous than air • Water has a heat transfer rate 24 times greater than air at the same temperature • Sea water has high salinity (~35 ppt) • Increased pressure = for every 10 m, 1 atm(osphere) = 14.7 pounds per square inch (psi) • Dynamic oceanographic features affect prey density • Sea-surface temperatures, chlorophyll-a concentrations, upwelling, etc. • Integument • Body shape • Locomotion • Skeleton • Colour Patterns • Thermoregulation • Osmoregulation • Diving Physiology • Pressure smithsonianmag.com Adaptations Integument • Protective layer • Insulation/thermoregulation • Buoyancy • 50x thicker than terrestrial mammals • High cellular turnover rate • No sebaceous or sweat glands alaska-in-pictures.com • Multifunctional Body shape • Cetaceans are fully streamlined • Sirenians are less hydrodynamic • Pinnipeds are the least specialized Reproduced with permission from Catherine Hood savethemanatee.org Locomotion • Phocids – horizontal strokes with the hindlimbs • Otariids – use forelimbs for propulsion, and vertical strokes of hindlimbs to steer • Sirenians and Cetaceans – vertical strokes of fluke keepitupdavid.wordpress Speed (m/s) Average Sprint Human Pinniped Cetacean 0.9 (swimming) 5 2.8-5.5 1.7 (walking) 3.2 (running) 15 12.8 Polar Bear Sea Otter 2.8 (swimming) 1.4 8.3 (running) 2.5 earthguide.uscd.edu Pinniped skeleton • No bones in fluke • Reduced pelvic bone • Chevron bones support lumbar and vascular system • Fused arm joints • Fused neck vertebrae (7) • Reduced sternum and clavicle in odontocetes, none in mysticetes fr3.excedence.fr Cetacean skeleton Colour Pattern • How you look to predators and prey is important for survival • Caused by • Pigmentation • Diatoms • Scars (mostly males) • • • • • Countershading Prey stunning Species recognition Pod cohesion/coordination Indicates age and social status • Belugas are grey until the age of 10+ pic.people.com worldculturepictorial.com • Functions Delphinids • • • • • • Countershading Dark cape Dorsal overlay Bridle Eyepatch (orca) Flipper Strips • Common Dolphin has the most colouration Dawood • Wide range of colourations: • Generate large amounts of body heat • Shunt blood to flukes, flippers, tongue • Keep warm by: • Increased metabolism • Sea otter metabolism is 2.4x higher than a terrestrial animal of the same size • Increased insulation • Blubber is adipose tissue used for insulation, streamlining, buoyancy, and energy storage • Can be >30 cm thick animalspeciesdiscovery.wikispaces.com bio.research.ucsc.edu Reproduced with permission from Catherine Hood Thermoregulation Thermoregulation • Surface area:Volume ~23% smaller than terrestrial animals • More compact = less surface area to lose heat • Behavioural thermoregulation wallpaperflare.com • Pinnipeds: enter or leave water, seek shade, flip sand on back, dig holes to reach cooler sand, panting • Cetaceans: seek different water temperatures Countercurrent heat exchange Skin Core 18˚ 23˚ 28˚ 33˚ Venous blood Arterial blood 20˚ 25˚ 30˚ 35˚ Osmoregulation • High salinity seawater, no freshwater to drink • Metabolize water from food • When desperate, some pinnipeds will drink seawater = mariposia • Large, reniculate kidneys Reniculi – each a separate kidney Reproduced with permission from Catherine Hood (Beluga whale) Hoelzel 2002 • % body weight: terrestrial = 0.3-0.4, marine 0.4-1.1 Diving Physiology • The components of the oxygen pathway are the same in terrestrial and marine mammals • Terrestrial – oxygen pathway is always open • Marine – oxygen pathway is open at the surface and closed during diving (when the animal is exercising and demand is the highest!) • Can eat (esophagus) and breathe (trachea) at the same time without risk of choking Stephen Dawson The Mammalian Dive Response • Pulmonary, circulatory, and metabolic adaptations: • Some pinnipeds and cetaceans are deep divers • Sirenians, sea otters, and polar bears are shallow divers Annie Roth Apnea – cessation of breathing Bradycardia – slow heart rate Peripheral vasoconstriction Reduced aerobic metabolism Anaïs Remili • • • • Apnea • Cessation of breathing • …but when they do take a breath, they exchange a greater proportion of CO2 for O2 (~90% vs. ~10% for humans) • Efficient respiration • Smaller lungs than would be expected by body size (<1% vs. 1.76% for humans), but greater respiratory volume • Conscious control of each breath (unihemispheric sleeping) • Slow heart rate to ~1/10th of normal Goldborgen et al. 2019 – Blue whale Bradycardia Manatee Sea lion Bottlenose dolphin Killer whale Elephant seal Grey seal Heart rate (beats/min.) Surface Dive 50 30-40 150-250 20-50 101-111 30-37 60 30 103-112 20-50 119 4 Peripheral vasoconstriction • Restricts flow to all organs except the brain and heart • Kidneys and liver get variable flow • Skeletal muscles get severely limited flow Reproduced with permission from Catherine Hood • Magnitude depends on type and length of dive Reduced aerobic metabolism • Aerobic dive limit (ADL) is the duration after which there is a net increase of lactate (product of lactic acid), goes to an anerobic dive • Long recovery to balance pH of cells, but accumulation of lactic acid does not appear to slow them down or cause pain as it does in humans Nautilus Live • May have a greater ability to metabolize lactate Oxygen storage • Increased blood volume (3x humans) • Increased number and size of red blood cells librarything.com % of total storage Total (O2/kg) Lungs Blood Muscles Otariid 40 13 54 33 Phocid 60 7 65 28 Dolphin 35 22 30 48 Human 20 24 57 15 • Hemoglobin in the blood (1.5x humans) • Myoglobin in the muscle (10x humans) getbodysmart.com Rete Mirabile Reproduced with permission from Catherine Hood • Reservoir of blood with oxygen in muscles near spinal cord, flippers, and fluke • Myoglobin muscle protein stores oxygen and releases it when needed Routine and extended dives • Gastric, renal, and hepatic functions reduced • Metabolic function reduced 50% from resting metabolism Routine: Extended: • • • • Intermittent flipper strokes Low heart rate Rely on O2 from myoglobin in muscle Aerobic metabolism • Prolonged gliding to save energy • Dramatic decrease in heart rate (can be lower than resting) • Use myoglobin and anaerobic metabolism • Blood redistributed to obligate aerobic tissue (brain) • Shallow decompression dives before/after Pressure • Pressure of internal air spaces must match pressure outside of the body to avoid damage • In mammals, internal air spaces exist in the lungs and the facial sinuses/middle ear • Seals have complex vascular lining which engorges at depth to almost fill the cavities • Cartilaginous airways reinforced Decompression sickness/nitrogen narcosis • Air is 78% nitrogen, 21% oxygen • Nitrogen in the blood under pressure will cause bubbles • Before deep dives, marine mammals often exhale to avoid excess nitrogen • While diving, the pressure causes the lungs to compress qassimy.com • Pushes remaining air into the upper airway with one-way valves where nitrogen cannot enter the blood Take Home Messages • Water absorbs more heat, is more dense, and conducts sound faster than air, ocean water has high salinity • Thermoregulation includes counter-current heat exchange • Osmoregulation through reniculate kidneys • Four aspects of the Mammalian Dive Response • Pinnipeds and cetaceans have larger and more numerous red blood cells than terrestrial mammals • Rete mirable acts as reservoir of oxygen in blood and muscle • Most cetaceans have fused cervical (neck) vertebrae • Belugas and river dolphins do not • Least to most adapted to aquatic life • Polar bear < Sea otter < Otariids < Phocids < Sirenians < Cetaceans Thank You!