Reflective Tree Frogs

Adult R.exechopygus

Adult Rhacophorus exechopygus

As mentioned by Chris in his previous posts, one of the interesting adaptations we have been investigating is the ability for some amphibians to reflect light in the infrared spectrum. This may have multiple benefits; one to aid in camouflage, as this increases their ability to match the leaves that they sit on when resting, and a second to perhaps aid in thermoregulation. The reflectance has mostly been described in Central and South American species, such as the leaf frogs that we work with in The Vivarium.

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This ability has also been observed in unrelated species of amphibians from other parts of the world that also live in a similar way to leaf frogs and is a great example of convergent evolution; how unrelated species have evolved similar adaptations as they live within a similar environment.

newly-metomorphosed-r-exechophygus-copy-1

Young Rhacophorus exechopygus

One species that Chris and I are currently working with in the vivarium is the Tramlap Flying Frog, Rhacophorus exechopygus, from Vietnam and Laos. These are also a leaf sitting tree frog, much like their Central American counterparts we are used to working with in the Museum. Despite being completely unrelated to Phyllomedusine Leaf frogs we have found they also have the same ability to reflect infrared light. What is even more interesting is that the colour and pattern of the frogs changes visibly as they mature, (as seen in the image to the left and above).

We have found that their ability to reflect infrared in the non-visible develops with the visible change – young frogs almost completely lack the ability to reflect and then they gradually develop this as their skin colour visibly changes. The graph below shows the big difference in spectra between a young and adult frog’s ability to reflect in the infrared. Chris and I regularly meet in the vivarium to collect data from our frogs as they continue to grow and change colour, so that we can document the development of this amazing adaptation. Our findings will be published in the very near future.

Spectra graph

Difference in IR reflectance between a young and adult R.exechopygus (blue line shows level of increased reflectance in adult at approximately 700nm.

             Chris’s Research               Colour Changing Frogs 

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