Temporomandibular joint and Giant Panda\u2019s (Ailuropoda melanoleuca) adaptation to bamboo diet

Pekka K Vallittu,Jukka Salo,Pekka Niemelä,Ling Shanshan,Hemin Zhang,Huang Shan,Juha Varrela,Li Rengui

doi:10.1038/s41598-021-93808-2

Abstract

Here, we present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system. The giant panda in the wild and in captivity removes without an exception the outer skin of all bamboo shoots, rich in abrasive and toxic compounds, by the highly adapted premolars P3 and P4. The temporomandibular joint (TMJ) allows sidewise movement of the jaw and the premolars can, in a cusp-to-cusp position, remove the poorly digestible outer skin of the bamboo before crushing the bamboo with molars. Based on the evidence presented here, we suggest that adaptation of TMJ to lateral movement for enabling cusp-to-cusp contact of premolars is the crucial evolutionary factor as which we consider the key to understand the Ailuropodinae lineage adaptive pathway to utilize the bamboo resource.

Highlights

We present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system
Our observations show that during the skimming of bamboo, the giant panda uses lateral movement of the mandible to bring the premolars to cusp-to-cusp position which is necessary for removing the outer layer of the culm
In June 2019, the skulls of two giant pandas were examined from the collection of the CCRCGP

Summary

Introduction

We present new evidence that evolutionary adaptation of the Ailuripodinae lineage to bamboo diet has taken place by morphological adaptations in the masticatory system. The temporomandibular joint (TMJ) allows sidewise movement of the jaw and the premolars can, in a cusp-to-cusp position, remove the poorly digestible outer skin of the bamboo before crushing the bamboo with molars. Based on the evidence presented here, we suggest that adaptation of TMJ to lateral movement for enabling cusp-to-cusp contact of premolars is the crucial evolutionary factor as which we consider the key to understand the Ailuropodinae lineage adaptive pathway to utilize the bamboo resource. In the evolutionary adaptation of the giant panda from omni/carnivore to herbivore, mechanical processing of the cellulose-rich food has exerted significant evolutionary pressure on its masticatory function, leading to changes in the morphology of the teeth. For cutting or grinding function of teeth cusp-to-cusp position of upper and lower teeth by lateral movement of the mandible is typically needed

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