Sticking/Climbing Ability and Morphology Studies of the Toe Pads of Chinese Fire Belly Newt

The Chinese fire belly newts (Cynops orientalis) have the ability to escape from the glass tank with vertical walls. An experimental device was developed to investigate the sticking and climbing behaviors of the newts. The detaching angles of the newt on the surfaces of glass, PMMA, and SUS 304 stainless steel at dry, little-water, and plenty-water conditions were measured and used as an index to evaluate the sticking and climbing abilities of the newts on tilted surface. The experimental results show that the newts have a strong ability to stick on tilted surface, particularly on the surface with little water. Morphological studies of the toe pads and belly were carried out by SEM and cryo-SEM to clarify the sticking mechanisms. It is found that the toe pad of the newt consists of a dense array of nanopillars with ca 100 nm - 300 nm diameter surrounded by small channels. This structure is supposed to facilitate high adhesion to substrate by providing capillary forces, and promote the squeeze-out of fluid between the toe pad and substrate in flooded case.