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Ontogenetic scaling of scansorial surface area and setal dimensions of Chondrodactylus bibronii (Gekkota: Gekkonidae): testing predictions derived from cross-species comparisons of gekkotans


Anthony P. Russell, Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada T2N 1 N4. E-mail:;;


Little is known of how the adhesive apparatus of gekkotans scales with growth. Cross-species comparisons of certain characteristics, using size as a comparator to investigate scaling relationships, suggest certain relationships between subdigital pad area and body size. The manner in which the adhesive apparatus grows and scales within any one species, however, remains unknown, and it is unclear whether interspecific and intraspecific patterns are similar. To address this, we examined a post-hatching ontogenetic series of the southern African gecko Chondrodactylus bibronii and demonstrate that setal density, setal basal diameter and setal spacing remain relatively constant in relation to size, indicating conserved subdigital pad assembly rules that are independent of size. Conversely, however, average and maximal setal lengths increase slightly and isometrically with size, an outcome that is probably explained by setal row recruitment, and the surface area of the subdigital pads scales close to, but below, isometry with respect to body mass and snout–vent length, it therefore does not increase sufficiently with size to compensate for the increase in mass. As a result, relative adhesive capacity decreases with growth with a regression slope of –0.45.