| Geometric-morphometric analysis is growingly used to quantify/analyze biological forms and discriminate among subtle variation in shape. The hermit crab “Clibanarius signatus” showed subtle heterochely; therefore, geometric morphometric analysis helps to determine visually these shape changes. Individuals of “C. signatus” were collected from a mangrove site on the Egyptian Red Sea coast. The present study aimed to: "1" detect the different types of asymmetries in C. signatus by geometrics morphometrics, "2" inspect the responsibility of occupied shell type on the chelae asymmetry, "3" investigate the asymmetry-types' differences between sexes, "4" use the fluctuating asymmetry as an indicator for developmental stability, "5" and to investigate morphological, developmental, and functional modularity in the chela compartments. Directional and fluctuating asymmetries were detected; both showed high size levels in the males than in the females. The males revealed a high-level of shape directional symmetry and low-level of shape fluctuating asymmetry compared with the females. All investigated individuals showed larger right chela. The fluctuating asymmetry may be attributed to developmental instability as a result of occupying dextral shells. The integration and |
modularity of the chela compartments revealed two developmental modules, which morphologically and functionally integrated as one module. The individual variation and the fluctuating asymmetry showed similar patterns indicating that the same developmental processes are contributed to the chela shape variation. The present results are indicative signs that environmental stress is present and sufficient to produce asymmetry in chelae size/shape. However, this asymmetry was subtle, suggesting that it does not produce notable variation in the chelae functions.