G. a. leiurus , G. a. semiarmatus and G. a. The dorsal and pelvic spines are protected from collapse by a pelvic girdle that connects them in a strong, crush-proof structure surrounding the body.
Colour varies due to location and conditions.
During the breeding season males develop a red breast. Mainly found in freshwater. G. a. trachus . The most heavily armoured, the body is fully plated and all spines are present. This variety is found in salt water, estuaries and is the main freshwater type in Eastern Europe.