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Case Study: Understanding bony tissue in lizard skin
Modelling osteoderms (bony deposits in the skin) of different lizard species, to investigate their purpose.
13 October 2022
Some animals – including turtles and crocodiles – have osteoderms within the skin. These bony deposits are also present in some species of lizards, but not in others. Some lizards have osteoderms in one part of the body, while others might have them all over the head and body. The osteoderms show great variation in their structure but scientists do not yet understand why lizards show such diversity in their osteoderms.
In response to this question, Professor Moazen from UCL Mechanical Engineering created a joint collaboration between mechanical engineers and cell and developmental biologists. The team includes experts from UCL (Professor Susan Evans [Biosciences] and Dr Sergio Bertazzo [Medical Physics/Biochemical Engineering]), Imperial College London (Dr Arkhat Abzhanov) and collaborators in Canada (Dr Matthew Vickaryous) and France (Professor Anthony Herrel). The project commenced in 2017 and is funded by the Human Frontier Science Program.
Modelling lizard diversity
“We don't understand why lizards show such remarkable diversity,” Professor Moazen explains. “We don't see this level of diversity in any other groups. This raises many questions. What drives this diversity? What do osteoderms do? Do they protect the lizards’ bodies, or do they do something else?”
This was the team’s starting point for the project. The biologists on the team have been exploring which genes are responsible for the formation of osteoderms, and are trying to pinpoint the relevant signalling pathways and developmental processes. For Professor Moazen and his other mechanical engineering colleagues, the focus has been on modelling and characterising lizard osteoderms as well as understanding their mechanical properties.
Since there are over 4,000 lizard species, the team has selected around 15 species for this project. These species have been carefully selected to sample lizards from different groups and different lifestyles/environments, to explore possible correlations between environment, climate, diet and biomechanics.
The modelling work has been made possible by advances in scanning technology. “There has been a massive development in imaging techniques, and in serial characterisation techniques, over the last 20 to 30 years,” Professor Moazen explains. “Using these tools, in combination with novel modelling approaches, we can address long-standing questions and test competing hypotheses.”
Understanding nature to find opportunities
Some of the early results of this research indicate that osteoderms might help with skull function as well as protection. “One of our hypotheses is that osteoderms in the lizard head help them during feeding,” explains Professor Moazen. “We’ve gathered evidence that these tissues contribute to the mechanics of the skull. Where osteoderms are tightly connected to their skulls, they potentially reduce the loading that is applied to the skull during feeding.” The presence of osteoderms in the skull may, therefore, enable a lizard to bite harder. This, in turn, may help them achieve a more diverse diet in places where food resources might be limited.
“This research is very much basic science,” says Professor Moazen. “But it’s an area that we think has lots of future potential. If you have a structure in nature that you don’t understand, you can’t do anything with it.” Once the team has found answers to their questions, they believe there could be many future opportunities.
“We may discover new materials or new composite structures that nature has developed and optimised over millions of years.” Professor Moazen explains. “We are trying to understand how those ancient composites are structured so that we can go on and replicate them. We can learn from nature and develop new devices for protection, for example in helmets. It can also enable us to design structures inspired by nature for other applications.”