A contribution to the functional analysis of the foot of the Tokay, Gekko gecko (Reptilia: Gekkonidae)

The foot of gekkonid lizards, because of the wide range of variation it displays within the family, is an ideal system on which to carry out a functional anatomical study. The wide range of variability and adaptation of the foot is unparalleled in other lizard groups. The Tokay ( Gekko gecko (Linnaeus) 1785) has been used as a basis for a broader study of the comparative and functional anatomy of the foot within the family Gekkonidae. The acquisition of adhesive pads by Gekko has resulted in the development of a very distinctive mode of locomotion which has become modified both to deploy and, at the same time, protect the delicate subdigital setae. Analysis of the structure and function of the foot has been carried out in two stages: firstly a description of the mechanical units and then an interpretation of their function, with the aid of high speed cinematographic data. The skeletal elements of the foot exhibit several features which reflect the specialized method of locomotion and these are related to remarkable adaptations exhibited by the associated muscular, vascular and tendon systems. The functional significance of scansorial plates is discussed and the relationship between size and locomotory ability within the family Gekkonidae is also considered. Some ideas as to the selective advantage of the particular locomotory modifications under discussion are presented, but further consideration of this topic must wait until subsequent papers deal with a larger proportion of the family.