Meeting Abstract

88.2  Thursday, Jan. 7  Modulation and modularity : behavioral insights into secondary reduction and loss of the gekkotan adhesive system RUSSELL, Anthony P.*; HIGHAM, Timothy E.; University of Calgary; Clemson University arussell@ucalgary.ca

The subdigital adhesive pads of geckos consist of a hierarchy of structural components. The epidermally-derived setae are the ultimate agents of adhesion, but their action is dependent upon a suite of morphological components that control the pattern of application and release of the setae. Whether or not the adhesive system is deployed in any given situation is dependent upon sensory feedback relating to body orientation. In horizontal locomotion the digits are carried in a permanently hyperextended configuration, regardless of the challenges of traction that may prevail. Despite the many advantages that the adhesive system may confer, some lineages of geckos have secondarily reduced or lost it as a functional entity. The pattern of reduction or loss is suggestive that the adhesive apparatus is an integrated developmental and evolutionary module. The pattern of reduction and loss is typified by a distal shift and truncation of the apparatus, resulting in a diminution in the number of scansors involved, and ultimately a breakdown in the orderly arrangement of the setal fields. Ecological circumstance and behavioral control collectively correlate well with reduction and loss of this system. Examples from African geckos occupying diverse habitats and trending towards secondary terrestriality will be used to illustrate the morphological transformations that exemplify reduction and loss, and to explore how these changes lead to new patterns of adaptation and new configurations of the modular system.