Morphological Adaptations of Polar Cod Boreogadus saida (Gadidae) to a Life in the Ice Conditions

Illustrated description of the scales of the cryopelagic polar cod (Boreogadus saida) is given for the first time. Scale cover in this species is formed by the ordinary cycloid scales as well as a rather numerous additional spiny bony plates, which superficially resemble placoid scales. We hypothesize that these spiny bony plates probably perform a several functions, namely, reduce the turbulence of the water flows in the boundary layer of the body, protect the skin from damage by the sharp edges of ice sludge and ice floe, serve for increasing the buoyancy of the body, especially in the coastal low-salinity waters of the Arctic. Scale cover in gadid co-habitant Arctic cod Arctogadus glacialis is formed by the smooth cycloid scales only without spiny bony plates.