[2][3][4] Their eyes are of medium size and are set towards the top of the head, indicating that they catch prey by moving into the water column from the seafloor.
[2][3][4][5][6] Only Artedidraconids have chin barbels hanging from the lower jaw that drags through the sand and a hook shaped operculum.
[5] Notothenioid fish dominate the Southern Ocean diversity and biomass largely because of the pelagization by some species.
Evolution that decreased the amount of minerals present in the skeleton and increased the number of lipids in the body made this possible.
Antifreeze glycoproteins bind to ice that enters the body through ingestion of food, water and from their environment to prevent the organism freezing internally.
[9] They consist of repeating amino acids alanine-alanine-threonine to effectively bind to ice molecules and render them as non-threatening to survival.
[10] AFGPs are created in the pancreas and are released into the digestive tract to wrap around ice crystals so they can be safely excreted with excrement.
[11] Heat shock proteins (HSPs) are expressed during exposure to high temperatures and is a characteristic held by most organisms.
[9] HSP expression indicates that regulation of Hsp70 occurred once during speciation, showing that it is a trait of most, if not all Antarctic notothenioids possess.
[9] Some Antarctic fish are able to resist perishing when exposed to temperatures 13–18 °C (55–64 °F) higher than their environment but little research has taken place to explain how they survive.
Genetic evidence shows that crocodile icefish had erythrocytes but have back evolved to not use hemoglobin, or any protein binding for oxygen transport.
[9] One other possible explanation is that colder waters increases the viscosity of body fluids to the point that it is beneficial to eliminate erythrocytes altogether, and instead rely on adaptations.
Once hatched, the larvae have sufficient means to swim and evade predators with long, slender bodies and larval fins.
[17] Adaptive radiation is the rapid speciation of multiple species from a common ancestor to fill empty niches.
Evidence of adaptive radiation is common ancestry, early bursts of speciation that decrease with time and a correlation between phenotype and environment.
The mass extinction created many open niches for Antarctic notothenioids to colonize, triggering adaptive radiation.
AFGPs do not fit with the early burst model because they were developed in Antarctic fish 10 Ma before rapid speciation.