Why Don’t Fish Freeze By:Rachel Brayley

Why do some fish need antifreeze? Who needs it? How does it work? Other adaptations to the cold. What can be done with antifreeze?

Why do some fish need antifreeze? Live in Antarctic Ocean Water less than 0°C Always at or below freezing point Ice crystals in water

Ice crystals Problem? X

Who? Antarctic fishes Antarctic cods Icefishes Antarctica South pole Antarctica North pole or South pole?

Antarctic cod Largest of the Antarctic fishes Grow up to 5 feet Average weight 55lbs Mostly a benthic fish Credit:www.fishbase.org Credit:http://www.photolib.noaa.gov

Icefishes Snout projects forward and is depressed Pelagic Also called “whiteblooded” fish Credit:www.fishbase.org Credit:http://www.johnjemerson.com/ Credit: http://www.victory-cruises.com

Similar? Crocodile Icefish Credit:http://www.botswana-tourism.gov.bw Credit:www.fishbase.org

So why don’t they freeze? Antarctic cods Protein “antifreeze” in blood Lowers the freezing point of body fluids below the freezing point of the seawater Attach to and prevent the further growth of ice crystals Credit:http://www.photolib.noaa.gov

Ice crystals Prevention

Another adaptation to the cold Icefishes Doesn’t keep them from freezing Lack hemoglobin in blood Evolved without it because don’t need it What is hemoglobin?? Credit: http://library.thinkquest.org/

Hemoglobin Part of red blood cells Transports oxygen in blood O2 Organs Cells, etc.

How do they live without it? Transport oxygen with plasma instead Able to do because: Live in highly oxygenated environment Excellent blood circulation Credit:http://www.icefish.neu.edu/

What can be done with fish antifreeze? Winter Flounder Cold stimulates production of antifreeze Antifreeze gene Atlantic salmon growth rates Credit:www.fishbase.org Credit:http://www.vanaqua.org/

What have we learned? The 2 kinds of fishes that have adapted to extremely cold water are: Antarctic cods Icefishes These fish live in the: Antarctic Ocean What is the adaptation that Antarctic cods have that keeps them from freezing? Antifreeze proteins What have Icefishes evolved without because they don’t need it? Hemoglobin What kind of fish are antifreeze genes from Winter Flounder being used in? Atlantic Salmon

Questions??