( Very thin but hardy unblemished skin a...)Thin tough skin, slow-growing gills protect larval Antarctic fish

Such adaptations are important, researchers at the University of Illinois atUrbana-Champaign say, because the larval fish of at least two species of notothenioids that inhabit the Ross Sea at McMurdo Sound and Terra Nova Bay surprisingly lack sufficient antifreeze to protect them through their first three months of life.

The unexpected discovery, reported online by the Journal of Experimental Biology ahead of regular publication, counters the assumption that these vital proteins must be present from the time of hatching -- a view held by scientists since fish AFPs were found in the 1960s.

Internal fluids such as blood in many notothenioids are about half as salty as seawater. While seawater reaches its freezing point at -1.91 degrees Celsius, fish fluids will freeze at about -1 degree Celsius. The water where these species dwell rarely rises above the freezing point and is regularly filled with ice crystals.

"The way that we've understood how adult polar fishes survive has been based on their use of these antifreeze proteins to lower the freezing point of their internal fluids," said lead author Paul A. Cziko, a research specialist in the department of animal biology. "We finally got a chance to look at the larval fish, and it seems that they don't always have to have antifreeze proteins to survive."

Cziko, who earned bachelor's degrees in honors biology and biochemistry in 2004 from Illinois, studied in Antarctica as an undergraduate with animal biology professors Chi-Hing (Christina) Cheng and Arthur L. DeVries, who discovered AFPs in notothenioids.

The research team, which also included Clive W. Evans of the University of Auckland in New Zealand, studied three notothenioid species
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Source:University of Illinois at Urbana-Champaign