Life in Freezing Environments

Question 1

What temperature does seawater freeze at?

Answer 1

-1.9 degrees

Question 2

What temperature do normal fish freeze at?

Answer 2

0.6 degrees

Question 3

What temperature do normal invertebrates freeze at?

Answer 3

-1.9 degrees (haemolymph)

Question 4

Freeze intolerant organisms use supercooling; what is this?

Answer 4

supercooling is used by arctic fish and is a process of cooling a liquid to below its freezing point without the liquid becoming a solid

Question 5

Freeze intolerant organisms also use colligative antifreezers; what are these?

Answer 5

Colligative antifreezes depress the freezing point of a liquid; lowers the freezing point in proportion to concentration (Na+Cl- vs Glycerol). Colligative antifreezes are used by invertebrates

Question 6

What mechanisms do antarctic fish and invertebrates use to resist the cold

Answer 6

Non-colligative antifreezes

Question 7

What do non-colligative antifreezes do?

Answer 7

dont lower the freezing point but act at low concentrations (have a low osmotic effect) = antifreeze proteins (AFPs)

Question 8

How are AFPs seen in both antarctic and arctic species?

Answer 8

Convergent evolution

Question 9

What are AFPs

Answer 9

Glycoproteins and peptides; macromolecules with small osmotic activity

Question 10

How do AFPs work?

Answer 10

They bind to ice crystals and prevent growth

Question 11

What do Freeze tolerant organisms use?

Answer 11

Ice nucleating agents (INAs)

Question 12

How do INAs work?

Answer 12

INAs catalyse the formation of ice in the ECF
This increases the osmolarity of the ECF
The freezing point of the ECF decreases
H20 from the ICF diffuses into the ECF
The ICF now has a lower freezing point

Question 13

How can the Atlantic blue tuna survive in cold conditions?

Answer 13

• Efficient counter-current heat exchange; rate miracle for a ‘wonder net’ with cutaneous vessels
• lots of red muscle that produces heat instead of ATP - high metabolic rate of dark lateral muscles generate metabolic heat

Question 14

What does the eye muscle do in the Billfish?

Answer 14

ATP creates heat instead of muscle contraction

Question 15

What does the viscosity of blood or organisms depend on?

Answer 15

• Plasma Viscosity (temp and antifreeze proteins)
• Hematocrit (low/highly variable)
• Red blood cell deformity (nucleated red cells/effect of catecholamine)

Question 16

What adaptation does the ice-fish have?

Answer 16

The only adult vertebrate to lack red blood cells

Question 17

How did the mutation (no RBCs) arise?

Answer 17

There was a mutation in the gene coding for beta and alpha - globin production

Question 18

What is the blood oxygen carrying capacity of the icefish compared to red-blooded species?

Answer 18

10%

Question 19

What features does the ice-fish possess that make it different from normal fish?

Answer 19

• Large heart (high cardiac output)

- Large capillaries for low vascular resistance (and low blood pressure)