The giant panda's mystery revealed
The evolution of the temporomandibular joint and premolar teeth enabled adaptation to bamboo diet

Date:
July 9, 2021
Source:
University of Turku
Summary:
Although the giant panda is in practice a herbivore, its masticatory
system functions differently from the other herbivores. Through
the processes of natural selection, the giant panda's dietary
preference has strongly impacted the evolution of its teeth and
jaws. Researchers have solved the mystery of how the giant panda's
special stomatognathic system functions.



FULL STORY ========================================================================== Although the giant panda is in practice a herbivore, its masticatory
system functions differently from the other herbivores. Through the
processes of natural selection, the giant panda's dietary preference
has strongly impacted the evolution of its teeth and jaws. Researchers
from the Institute of Dentistry at the University of Turku and the
Biodiversity unit of the University of Turku together with researchers
from the China Conservation and Research Center for Giant Panda (CCRCGP)
have been the first in the world to solve the mystery of how the giant
panda's special stomatognathic system functions.


==========================================================================
The bamboo diet of the giant panda (Ailuropoda melanoleuca) has long
been a mystery for researchers. The panda is in practice a herbivore,
and its diet only consists of few dozen species of bamboo. Related to
the consumption of bamboo, the giant panda has a special characteristic
of peeling the green outer skin of all bamboo shoots, rich in abrasive
and toxic compounds, by the highly adapted premolars.

Herbivores have usually evolved to have ridged molars that help them
grind the plant material and jaws capable of moving sideways which is
essential for grinding their food. Although the teeth of giant pandas have
been studied extensively, until now, researchers have not paid attention
to why the large canines of their upper jaw do not prevent the sideways movement of the lower jaw typical for herbivores -- and also humans. The
key to this has been the evolution of the temporomandibular joint and
the premolar teeth.

Evolution of the Temporomandibular Joint Allows Sideways Movement Using
modern 3D scanning methods, the research group studied the movement
of the giant panda's jaw and the structure of its teeth and found the
answer to the question that had puzzled researchers for over a century:
how are giant pandas able to use bamboo as their diet. The solution
was that the panda's temporomandibular joint has evolved to differ from
that of e.g. brown bear and polar bear. In addition to the open-closed
movement reminding that of a hinge, the joint also allows the jaw to
be moved sideways, which is required to peel the bamboo. Interestingly,
this movement isn't prevented by the large canines the male pandas need
to fight.

- The necessity to ensure adequate nutrition has helped evolve the temporomandibular joint and the shape of the teeth to allow efficient
peeling of the bamboo without without exposing the premolars to the
attritive or other damaging effect of bamboo diet, explains Professor
Pekka Vallittu from the Institute of Dentistry.

The evolution of the giant panda's masticatory system, as demonstrated in
the study, allowed them to be the only large mammals to access an endless source of nutrition in the form of bamboo in the early Pleistocene.

- The premolars giant pandas use for peeling bamboo are unique among the
family of bears and allow the removal of the poisonous green skin of the
bamboo which also includes mineral crystals which would wear their teeth,
says Professor Juha Varrela from the Institute of Dentistry.

The study of how the giant panda's masticatory system functions also
helps to understand human's occlusion and its characteristics better.

- Whether giant pandas grind their teeth still remains to be seen,
ruminates Vallittu.

- This newly published study is of great scientific significance because
it solves the long-prevailing mystery of the ecological interrelationship between the pandas and the bamboo plants, says Professor Jukka Salo from
the Biodiversity Unit of the University of Turku.

========================================================================== Story Source: Materials provided by University_of_Turku. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Pekka K. Vallittu, Juha Varrela, Jukka Salo, Li Rengui, Ling
Shanshan,
Huang Shan, Hemin Zhang, Pekka
Niemel�. Temporomandibular joint and Giant Panda's
(Ailuropoda melanoleuca) adaptation to bamboo diet. Scientific
Reports, 2021; 11 (1) DOI: 10.1038/s41598-021-93808-2 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210709104215.htm

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