Page 21 - eclipse - Autumn 2018

How frogs use their unique skeletal anatomy to improve their jumping ability
“We are particularly excited about this study because we think our methods open new doors for exploring how specific anatomical features affect animal locomotion.”
Dr Christopher Richards, Research Fellow in Paleorobotics at the RVC
As well as their long legs,
a particularly striking feature of a frog’s skeletal anatomy is a sharp bend in their
lower back. Underlying this bend is
the ilio-sacral (IS) joint – a hinge-like pivot which allows the frog to control the angle between its upper and lower body. The IS joint is folded when a frog is sitting at rest to allow the frog to crouch closely to its perch.
During the explosive early moments of a jump, a frog’s muscles extend the IS joint to rapidly straighten its back. Biologists previously believed the IS hinge was an essential part of the anatomy, allowing a force transfer between the upper and lower body of the frog which enabled the jump.
However, the recent RVC study was able to show that, contrary to prior understanding, this IS extension is not
required for jumping but more of an evolutionary innovation for fine-tuning a frog’s jump performance.
The research team, which consisted
of Dr Christopher Richards, Dr Amber Collings and Enrico Eberhard, developed a simulation of a frog jumping using 3D computer technology. This simulation model was unique because it allowed the researchers to calculate the frog’s push off from the ground, rather than directly measuring it. From further analysis
the team were also able to isolate the influence of the IS joint by changing its action, whilst maintaining the consistency of all other body motions.
This research, which was funded by a European Research Council Starting Grant, was published in Royal Society’s Biology Letters in September. The article is entitled: ‘The dynamic role of the ilio-sacral joint in jumping frogs’.
Dr Richards, Research Fellow in Paleorobotics at the RVC, said: “We are particularly excited about this study because we think our methods open new doors for exploring how specific anatomical features affect animal locomotion.”
RESEARCH NEWS
21