Conservation and Ecology of Marine Reptiles MARE 494 Dr. Turner Summer 2007

1. Conservation and Ecology of Marine Reptiles MARE 494 Dr. Turner Summer 2007

2. Diving Physiology Among longest and deepest diving vertebrates Spend 3-6% time at surface Central features of dive ability: efficient O2 transport tolerance for hypoxia maximum used of limited O2 stores

3. Diving Physiology Physiological traits of breath-hold mode are common reptilian traits Present in land-dwelling ancestors However, several distinct modifications to marine existence parallels with marine mammals

4. Dive Records

5. Lung Structure & Function Few breaths (2-3s) at surface to empty & refill lungs # breaths (time at surface) to increase with duration of submergence time Tidal lung volumes greater than terrestrial or aquatic reptiles marine mammals have greater tidal volumes than terrestrial

6. Lung Structure & Function Similar structure to marine mammal lungs Large-diameter airways are well enforced cartilaginous bronchioles smooth muscle with elastic fiber matrix Lack a diaphragm Pelvic, gular, & pectoral muscles ventilate lungs

7. Lung Structure & Function Otariid Odobenid Phocid

8. Under Pressure Tolerate ↑ in water pressure 1 atmosphere (atm) for each 10m Leatherback > 1000m (100atm) Squeezes air-filled spaces Absorbing gases at high pressure can be toxic – damage from bubbles Effect upon central nervous system

9. In Fact It’s a Gas Sea turtles have the highest rates of O2 consumption and greatest aerobic scopes of any reptile Can attain resting O2 consumption rates similar to rates of mammals Greater area for gas exchange (diffusion) than most reptiles; lower resistance

10. It’s a Gas Gas Gas High pulmonary diffusion capacity – advantage during prolonged submergence when sea turtles deplete lung, arterial, & venous O2 stores Low-resistance lung – support high metabolic rates (maximum exercise) by maintaining high saturation levels in arterial blood

11. It’s a Gas Gas Gas High pulmonary diffusion capacity – advantage during prolonged submergence when sea turtles deplete lung, arterial, & venous O2 stores Low-resistance lung – support high metabolic rates (maximum exercise) by maintaining high saturation levels in arterial blood

12. Hope Floats Regulate volume of air in lungs during shallow dives for buoyancy control fine-scale – shifting among compartments Also thought to quickly distribute blood warmed via heliothermy

13. Oxygen Transport Dive duration a function of total O2 store and metabolic rate during the dive metabolic rate a function of: Size Activity Temperature Hormonal status Dietary status O2 consumption – VO2

14. STÖR Diving birds & mammals typically store O2 in blood & tissues Amphibians & reptiles use lings as major O2 stores Sea turtles – may center around shallow versus deep diving

15. SHØP Shallow divers (Cheloniids)– depend upon lung as the major O2 store Deep divers – (Dermochelyids) rely upon blood and tissue stores for O2 Hematocrit, hemoglobin, myoglobin concentrations among highest in reptiles similar to levels in marine mammals

16. Total Body Oxygen Stores Largest O2 stores in diving mammals Hemoglobin – O2 binding molecule of red blood cells; can deliver O2 where needed Myoglobin – O2 binding molecule of muscle cells; delivers O2 directly to muscles Hematocrit – packed red blood cell volume; hemoglobin volume – higher in mammals with increased diving capacity

17. Total Body Oxygen Stores Resp – Cardio – Cellular = All Equal Fewer mitochondria Cellular dominant More mitochondria

18. Total Body Oxygen Stores Respiratory properties of blood depends upon whether O2 is primarily stores in tissues or in the lung High hematocrit in leatherbacks – similar to marine mammals

19. Total Body Oxygen Stores

20. Total Body Oxygen Stores

21. Dive Response During dive, available O2 ↓ (hypoxia) and CO2 ↑ (hypercapnia) Together create asphyxia Counteract with several adaptations: Anaerobic diving – no O2; lactic acid & H+ ions accumulate Bradycardia – decline in heart rate Ischemia – preferential distribution of blood to O2 sensitive organs; temperature & metabolic rate

22. Diving Adaptations Cease breathing during diving events apneic conditions – conflicting conditions 1. O2 stores ↓ with ↑ activity (O2 demand) 2. CO2 & lactate ↑ in blood & muscle During hypoxic events, muscle activity is maintained anaerobically results in ↑ accumulation of lactate

23. Low-Impact Aerobics In the past 10-20 yrs – research emphasis on anaerobic dive physiology Recent on aerobic dive limits and how animals stay within these limits Know that aerobic diving is the only way to facilitate multiple sequential dives over a short period of time

24. Aerobic Dive Limit Longest dive that does not lead to an increase in blood lactate concentration If dive within ADL, can dive again immediately without recovery period If dive exceeds ADL and accumulate lactate; surface recovery period is required to “burn-off” (remove) lactic acid from the body

25. Aerobic Dive Limit

26. Total Body Oxygen Stores Leatherback

27. Anoxia Vertebrate brain has an absolute dependence upon O2 and dies within a few minutes without it Ultimate determinant of dive endurance in marine mammals Some FW & sea turtles can survive several hours of anoxia

28. Anoxia “You have an absolutely unique genetic condition known as ‘Homer Simpson syndrome’. Why, I could wallop you all day with this surgical two-by-four without ever knocking you down. But... I have other appointments.” – Dr. Julius Hibbert Unique mechanisms to protect brain Anoxic turtle brain can maintain ATP levels & ionic homeostasis by severely reducing metabolic demands to a level met by anaerobic glycolysis In FW turtles – used to survive hibernation

29. Hibernation In FW turtles – used to survive hibernation in frozen over hypoxic ponds In Sea Turtles??? Torpid hibernating sea turtles – may survive 1-3 months (presumably without eating or breathing) Know that cold can effect some animals “cold stunned” coma

30. Diving Pau Huge gaps in knowledge (sounds familiar?) Possibly with newly developed sensors… In order to reduce deaths in fishing gear… Maybe Sargassum has an effect???