[Comparative study of the dendritic spines in the principle cortical zones of the turtle forebrain]

A comparative investigation of dendritic spines has been performed in three cortical regions (dorsal, pyriform and hippocampal) of the forebrain cortical plate in the tortoise and turtle by means of light and electron microscopy. There are differences both between various cortical zones and at various levels of dendrites (proximal, middle and distal) within the limits of one cortical formation. The dorsal cortex has a number of signs demonstrating its more complex formation in comparison with the hippocampal and pyriform cortex. A possibility on homologicity of this zone with some mammalia is supposed. Owing to the data obtained, three groups of signs can be defined in the spinal organization of the cortical zones studied: common for all four species investigated (perhaps they are connected with a certain evolutional level in the neural system development), ecologically specific, those make difference between the tortoise and the turtle, and species-specific.