Morphology and morphometrics of the appendicular musculature in geckoes with different locomotor habits (Lepidosauria)

In this study a ground-dwelling (Eublepharis macularius) and a highly speci alised climbing (Gekko gecko) lizard were chosen as study objects. The fore - and hindlimbs of two individuals of each species were dissected, and musc le masses, mean fibre lengths, cross-sectional areas and moment arms were d etermined. Special attention was paid to general muscle architecture (origi n, insertion, fibre orientation, etc.) and pennation angles. Using these va riables (cross sectional areas and moment arms), maximal moments exertable across the shoulder/hip, elbow/knee and wrist/ankle were calculated for bot h species. In accordance with the biomechanical predictions related to the preferred locomotor substrate of each species (i.e. level running for E. ma cularius and climbing for G. gecko), the results of this study indicate tha t climbers such as G. gecko generally possess powerful retractor muscles cr ossing the shoulder and hip joints. Additionally, the specialised climber i s able to exert higher flexion moments across the elbow, which pre Vents th e animals from falling backwards. However, G. gecko appears to be constrain ed in its ankle extension capabilities by the presence of the adhesive toe pads. The level-running species, on the other hand, shows a relatively stro nger development of the extensor muscles in the lower limbs, allowing these lizards to run in an erect posture. In general, both species show large si milarities on a gross morphological level as expected when considering thei r phylogenetic relatedness. Adaptations to their preferred locomotor substr ate only become apparent when considering the functional properties (i.e. j oint moments) of the appendicular musculature.