Ectotherms Flashcards
Why do ectotherms have body temps close to their environment?
- small (high SA:V ratio)
- low rates of metabolism (i.e. heat production)
What is supercooling?
When the temp of body fluids is lowered to below freezing without the formation of ice.
What is the requirement for supercooling to occur?
No ice-nucleating agents (INAs) - act as a nucleus for the formation of ice-crystals
Give an example of an organism that is able to supercool?
Mites (Alaskozetes)
-36C
How do mites (Alaskozetes) survive frozen in ice throughout winter?
- evacuate guts to remove potential INAs, which may cause ice crystals
- produce anti-freeze compounds
How do springtails survive frozen in ice throughout winter?
Dehydrating to remove body water that could freeze
What does freeze susceptible mean?
Invertebrates that avoid tissue & body waters freezing
What is the term for invertebrates that avoid tissue & body waters freezing?
Freeze susceptible
What does freeze tolerant mean?
Invertebrates that allow the formation of ice in extracellular fluid of body
Give an example of an invertebrate that is freeze tolerant.
Limpets
- at high tides, body temp is same as sea water when immersed so don’t freeze
- at low tides, exposed to air temps of -30C. Up to 90% of body fluids may be frozen
- remaining 10% contains solutes at high conc
- tissues of animal distorted at freezing causes expansion
What do Antarctic limpets do to prevent extracellular ice propagation?
Secrete mucus around themselves
How can the freezing point of water be reduced?
Adding solutes to water
What do some insects produce to reduce their freezing points & supercooling points?
- sugar alcohol (e.g. glycerol) a cryoprotectant
Give 3 reasons why temperature compensation is made possible?
- isozymes
- membrane adaptations
- cryoprotectant synthesis
Why do fish require a large SA in gills to extract O2?
Low oxygen tension
