Adaptations for Diving Flashcards
What types of technology can be used to measure parameters during natural dives of mammals & birds?
- Time-depth recorder & logger
- GPS & satellite tags
- Automates blood sampling catheters
- PO2 electrodes/thermistors
- More recent devices allow recording of 3D dive profiles
Names 6 problems that can affect human diving
- Oxygen supply
- The bends
- Nitrogen narcosis
- Oxygen toxicity
- Direct effects of high pressure
- Squeeze
Give an example of an adaptation to diving in mammals + example species
Clue - RBC
- Elephant seals
- RBC increase
- Haematocrit increases from 38% to 80%
Give an example of an adaptation to diving in mammals + example species
Clue - blood vessels
- Dolphins
- Vasoconstriction peripheral blood vessels & reduce blood flow to muscles, digestive system, kidneys & other non-essential organs
- Weddell seals maintain blood flow to brain, retina & spinal cord - which are important in navigation & motor control
- Blood is directed to adrenal gland, which secretes cortisol, apparently important in stabilizing nerve ends and preventing High Pressure Nervous Syndrome (HPNS)
- In gentoo penguins, femoral blood flow decreased to about 25% that of birds swimming on surface, suggesting vasoconstriction is also important in conserving O2
Give an example of an adaptation to diving in mammals + example species
Clue - heart rate
- Bradycardia
- penguin heart rates decrease from about 227 to 80 beats min-1 and that of platypuses from 140-230 to 10-120 beats min-1
What is the end product of anaerobic respiration?
Lactic acid
Why is lactic acid an issue for diving mammals?
- Can upset acid-base & pH balance of blood
- Doesn’t enter bloodstream until animal surfaces & oxygen debt can be repaid as there is little circulation to muscles during diving
- Usually means a longer surface interval is needed before the animal can dive again
What is the Aerobic Dive Limit of Weddell seals?
19 mins
Why does the bends occur?
- N2 from air breathed is absorbed from the lungs by the blood during diving
- Blood & tissues under pressure become saturated with nitrogen and some is also absorbed by fat and fluid in the joints
- When the diver surfaces, the nitrogen comes out of solution & is returned to the lungs where it is exhaled
- If diver ascends too quickly, N2 cannot diffuse out fast enough and forms bubbles in the bloodstream & joints
- These can block capillaries & cause fatal disruption of blood flow and bubbles forming in the joints cause extreme pain (‘the bends’)
- Usually occurs in divers who breath air under pressure for long periods but can occur if the diver makes numerous repetitive dives to 10-20 m (e.g. pearl divers)
Why do many diving mammals not experience the bends?
- Many load the blood & muscles with oxygen on the surface & then exhale before they dive
- Removes most of the air from the lungs so there is little N2 to enter the blood
- Lungs are collapsed by water pressure at depth & any air left in them is forced into the trachea
- The trachea is cartilaginous & not vascularised, nitrogen cannot be absorbed across it into the bloodstream
When may gas emboli occur in diving mammals?
- When animals are forced to return to the surface from depth at a rate that does not allow them to manage the N2 levels
- Noise pollution (e.g. sonar and seismic testing) have been implicated in this & in mass strandings
What is nitrogen narcosis?
- Some gases, including N2, absorbed under pressure have anaesthetic or narcotic effects
- This effect in humans manifests itself at different depths depending on the individual
- Nitrogen narcosis, sometimes referred to as ‘rapture of the deep’ has effects similar to alcohol intoxication
- Can result in death through impaired concentration and judgement and irrational behaviour
- Diving animals appear to avoid the problem because they don’t inhale nitrogen under pressure
What is oxygen toxicity?
Pure oxygen at a partial pressure of about 2 atm (~ 10 m depth) is toxic & in humans and leads to convulsions & death
What do divers use to reduce PO2 and PN2?
- Trimix (O2, N2 & helium)
- Heliox (helium & O2)
How do diving animals avoid squeeze?
- Have few air sinuses in their bodies
- Exhale the air in the lungs before diving
- Rib cages are more flexible and, along with the lung, collapse at depth
