Phylogenetical aspects of brain gangliosides in vertebrates

Abstract

The concentration and composition of brain gangliosides in 78 vertebrate species belonging to the classes of Agnathes, Chondrichthyes, Osteichthyes, Amphibia, Reptilia, Aves and Mammalia were investigated. 1. An increase in the concentration of gangliosides takes place with anagenetic progress of nervous organization during phylogeny which is accompanied by a simultaneous decrease in the content of neuronal sialo-glycoproteins. This tendency can be observed in the main classes from cartilaginous fishes to mammals and also in smaller taxonomic units such as Elasmobranchia, Salmoniformes, Gadiformes, Percoidea, Notothenoidea, Rodentia. This indicates that gangliosides were more frequently selected than sialo-glycoproteins during vertebrate evolution. 2. Over a phylogenetic series the complexity of brain ganglioside composition is strikingly reduced. Among cold-blooded vertebrates a large number of complex and highly sialylated ganglioside fractions is present in the CNS, whereas in the warm-blooded birds and mammals only few fractions constitute the brain pattern, and these have less polarity. 3. The anagenetic change in the complexity of the brain ganglioside character is correlated to changes in the use of the three biosynthesis pathways of gangliosides (‘b’-pathway in Agnatha, ‘b’ and ‘c’ in cartilaginous and lower bony fishes, ‘a, b, c’ in ancient sturgeons and lungfish, ‘c’ in higher evolved bony fish, ‘b’, ‘c’ in amphibians, ‘b’ and ‘a’ in reptiles and birds and mainly the ‘a’-pathway in highly evolved mammals). 4. The data support the hypothesis that the great variations in concentration and composition of vertebrate brain gangliosides are not only dependent on the phylogenetic level of nervous organisation, but that they may also originate from the state of thermal adaptation. By these variations, vertebrates may be to maintain optimum rates of neuronal transmission while being adapted to different temperature habitats.