BRAIN GANGLIOSIDES AND COLD-ADAPTATION IN HIGH-ANTARCTIC FISH

The concentration and composition of gangliosides from the brain of ei ght species of Antarctic Notothenioid fishes belonging to the class of perciformes and two species of boreal fishes (tropic cichlid fish Ore ochromis mossambicus: Codfish Gadus morhua) were investigated. The con centra tion of whole brain gangliosides in Notothenioid fishes (betwee n 1622 and 2183 mu g NeuAc/g dry wt.) was slightly lower than that in the brains of fish species, which live in warm, temperate habitats (24 83 mu g NeuAc/g dry wt.). The composition of brain gangliosides was co mpletely different from that of warm adapted fish species (e.g. the tr opic cichlid fish Oreochromis mossambicus). The relative concentration of polysialogangliosides (GT1b-GH) is strongly increased in all the i nvestigated Antarctic species. They were found to have the most comple x and most polar brain ganglioside pattern (high degree of sialylation and alkali-lability) within the teleosts. This may be one of the mech anisms, beside antifreeze proteins, to keep the neuronal membranes fun ctional even below the freezing point.