Antarctic Fish Adaptations & Arctic vs. Antarctic Environments
Antarctic Fish Adaptations
Antarctic fish possess unique adaptations, including antifreeze glycoproteins, enabling survival in freezing Southern Ocean waters.
Without antifreeze glycoproteins, these fish would not survive in freezing waters.
Ice crystals are present in the water column and within the fish's blood supply.
Antifreeze glycoproteins are found in the blood and fluids bathing tissues but not inside cells, limiting synthesis.
These glycoproteins are produced in the pancreas, initially for dealing with ice crystals in the gut from ingested seawater.
The glycoproteins are secreted into the gut cavity and blood supply.
These fish have primitive, aglomerular kidneys that secrete urine instead of filtering it to prevent loss of antifreeze glycoproteins.
Ice crystals are found in the spleen, where they are removed by spleen cells via phagocytosis.
Red blooded notothenids injected with nanoparticles coated in antifreeze glycoproteins labeled with fluorescent dye showed fluorescence throughout the fish's body, indicating the presence of antifreeze glycoproteins.
The ocular fluid also contains antifreeze glycoproteins, preventing it from freezing and ensuring vision is maintained.
Besides the stomach, major organs do not contain antifreeze glycoproteins.
The spleen cells engulf ice crystals via phagocytosis; this is the only instance where ice crystals are found in cellular structures.
These fish also produce mucus to protect the skin from ice crystal penetration.
Antifreeze glycoproteins evolved from a trypsinogen-like serine protease gene, originally for protein breakdown in digestion.
Parallel evolution is seen in the Arctic, where the northern cod has antifreeze glycoproteins derived from a different gene.
Genomic studies show expansion in genes related to stress, including antifreeze and protection against reactive oxygen species.
Ice fish are vulnerable to warming waters and may struggle to adapt due to their specialized traits.
Arctic vs. Antarctic Environments
The Arctic and Antarctic are both harsh polar environments, but with marked differences.
Antarctica is isolated, covered by an ice sheet, surrounded by icy water, and has minimal contact with other oceans and no human inhabitants.
The Arctic Ocean is a sea surrounded by land, connected to the Atlantic and Pacific oceans, with a warming influence from both.
The Arctic Sea is shallow with more currents, making it less isolated than Antarctica.
The Arctic is inhabited by millions of humans.
Arctic Circle: Defined by latitude (66.33° N), with 24 hours of darkness in winter and light in summer.
Tree Line: Northern limit where conditions are too severe for tree growth (requires at least one month above 10°C).
The area of focus is the land masses fringing the Arctic Ocean, north of the tree line and within the Arctic Circle.
Arctic Sea Ice
Arctic sea ice is relatively thin (about 3 meters thick) and a mosaic of ice that breaks up and reforms, creating ridges.
Early explorers faced challenges due to ships getting stuck in the ice and moving randomly.
Polar Terrestrial Environments
Polar terrestrial environments have low temperatures, short growing seasons, low humidity, low incident radiation, and high winds.
These conditions lead to low productivity and impoverished environments.
The Arctic is less extreme than the Antarctic.
Temperatures vary with location and time. Temperature in the artic are much more variable than in antarctica.
Arctic temperatures are more variable and can exceed zero in summer.
Antarctic winter temperatures are much lower, barely exceeding zero in summer.
Permafrost underlies the surface, with a top layer that melts in spring, providing water for plants.
Arctic Terrestrial Fauna
The Arctic terrestrial fauna is more diverse than in Antarctica due to easier colonization and escape.
Arthropods: Approximately 2,000 species north of the tree line, dominated by flies (Diptera).
Insects tolerate freezing conditions in early life stages, with delayed development and univoltinism (reproducing once a year).
Many insects have reduced or lost wings due to high winds.
Mosquitoes are abundant in the Arctic during summer.
The Greenland moth takes 14 years to reach the adult stage, spending winters in diapause.
Abundant insects and plant life attract birds and mammals.
Fewer parasites and 24-hour daylight in summer are advantages for foraging.
Millions of birds migrate north in the summer, including eider ducks, barnacle geese, and Arctic terns.
The ptarmigan lives in the Arctic year-round and burrows into the snow during winter.
Predators (Arctic foxes) and herbivores (reindeers) are present.
Polar bears are top predators that feed on seals with subcutaneous fat.
Surviving Freezing Conditions: Cold Hardiness
Cold hardiness is the study of surviving sub-zero temperatures.
Strategies include avoiding body fluids from freezing or surviving the freezing of body fluids.
Adaptations involve behavioral, physiological, and biochemical adjustments.
Supercooling Curve
Supercooling curve helps us understand how animals freeze or avoid freezing.
Pure water can be supercooled below zero before freezing.
represents the temperature of the pure water sample.
The water cools below degrees, remaining liquid until it reaches the supercooling point, approximately degrees Celsius.
Freezing occurs, releasing heat of crystallization, resulting in a slight temperature increase.
represents the point at which the sample solidifies into ice.
Animals lower the freezing point (FP) and supercooling point (SCP) using various strategies.
Some insects can lower the SCP to degrees Celsius.