Passive Cushiony Biomechanics of Head Protection in Falling Geckos.

Hao Wang,Yi Song,Lei Cai,Zhendong Dai,Wenbo Wang

doi:10.1155/2018/9857894

Hao Wang, Yi Song + Show 3 more

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https://doi.org/10.1155/2018/9857894

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Abstract

Gekko geckos are capable to crawl on the steep even on upside-down surfaces. Such movement, especially at great altitude, puts them at high risks of incidentally dropping down and inevitable body or head impactions, though they may trigger air-righting reaction (ARR) to attenuate the landing shocks. However, the air-righting ability (ARA) in Gekko geckos is not fully developed. The implementation of ARR in some geckos is quite slow; and for those without tails, the ARR is even unobservable. Since ARA is compromised in Gekko geckos, there must be some other mechanisms responsible for protecting them from head injuries during falls. In this study, we looked into a Gekko gecko's brain to study its internal environment and structure, using the magnetic resonance imaging (MRI) technique. The results showed that the brain parenchyma was fully surrounded by the cerebrospinal fluid (CSF) in the skull. A succulent characteristic was presented, which meant the intracalvarium was significantly occupied by the CSF, up to 45% in volume. Then a simplified three-dimensional finite element model was built, and a dynamic simulation was conducted to evaluate the mechanical property of this succulent characteristic during the head impactions. These implied the succulent characteristic may play certain roles on the self-protection in case of head impaction, which is adaptable to the Gekko gecko's locomotion and behavior.

Highlights

Many animals in nature are able to crawl, climb, or run on different inclined surfaces, such as walls, ceilings, branches, and leaves, at a certain height above the earth
The published data [9] provided evidence that the air-righting abilities (ARA) probably starts developmentally as a reflex and within days/weeks mature into a central pattern generator (CPG) by showing that the completion of the air-righting reaction (ARR) maturation process had no dependency on loads attached to different parts of the body
This study investigated the internal environment and structure of a Gekko gecko’s brain qualitatively and quantitatively, in order to understand their mechanism underlying the selfprotection in head impaction

Summary

Introduction

Many animals in nature are able to crawl, climb, or run on different inclined surfaces, such as walls, ceilings, branches, and leaves, at a certain height above the earth. To avoid the body being injured when falling and impacting with the ground, animals have developed various abilities, such as air-righting abilities (ARA). Preventing the brain injury from the falling and impacting to the ground, a sort of self-protection is one of the important survival skills gained from natural selection and evolution in animals. The ARA might be weaker in Gekko geckos, because the relevant air-righting reflex did not mature, developmentally speaking, into a complete central program. When the falling height is not so high, the time for free fall is not sufficient for this performance Even though, it rarely causes any injury in the brain. It seems that Gekko geckos may possess certain characteristics to prevent themselves especially their head from injury caused by. A simplified mathematical model was built to qualitatively evaluate the corresponding mechanical property

Materials and Methods

Results and Discussion

Conclusion