Attachment of Turner's thick-toed geckos (Chondrodactylus turneri GRAY 1864) during weightlessness and their responses to flotation

Abstract

We investigated the behavior of 15 female Turner's thick-toed geckos (Chondrodactylus turneri GRAY 1864) during a 30-day orbital experiment on the unmanned spacecraft "BION-M" No. 1. During weightlessness, the geckos maintained their ability to attach to the surfaces using the subdigital pads on their toes. On average, the geckos spent 99.9% of the time adhering to surfaces during the flight and only 0.1% floating freely. The active geckos, when starting to float, immediately restored attachment by a number of behavioral responses. The floating quiescent geckos, when resuming their active condition, responded in the same manner. The responses during flotation are similar to the behavioral reflexes triggered by a fall under normal gravity; i.e.: 1) the ventral extension of the limbs, 2) a skydiving posture, and 3) postural righting reflexes. Ventral extension of limbs was described for the first time in weightlessness. Individual variability in the frequency of flotations was found for both active and quiescent geckos during the flight. The findings show that the ability to attach to surfaces is an important factor in the geckos' adaptation to weightlessness. The behavioral responses that originated during freefall in conditions on Earth (one-G) appear as adaptations to weightlessness and remain partially effective.

Keywords: Attachment to the surfaces; Behavioral reflexes; Flotation; Spaceflight; Turner's thick-toed gecko; Weightlessness.