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  • Amazon milk frog at Zoo Zurich.

    Deciphering blue bones

    The bones of the Amazon milk frog are turquoise blue. A research team is currently investigating exactly how they are constructed and what use they are to the frog. Our video shows the process.

    The Amazon milk frog's bones are truly special: they are turquoise blue. This unusual bone color has sparked the interest of scientists. In our video, we accompany researchers as they are investigating the details of the special bones.

    Video: Zoo Zurich, Nicole Schnyder, ARTORG Center

    The frog used in this video is a specimen from Zoo Zurich. It died of natural causes. Preserved in formalin, the frog embarks on a little «Tour de Suisse» in the service of research.

    Research curator Dr. Leyla Davis conserves a dead Amazon milk frog in formalin.

    Curator Dr. Leyla Davis preserves the dead frog in formalin. Photo: Zoo Zurich, Nicole Schnyder

    computed tomography reveals details

    The first stage on its itinerary took the frog to the Artorg Center for Biomedical Engineering Research at the University of Bern. Researchers there recorded the amphibian's anatomy in detail using computed tomography.

    ARTORG Center for Biomedical Engineering Research at the University of Bern; computed tomography of the Amazon milk frog (Trachycephalus resinifictrix).

    The computed tomography scanner provides a detailed image of the Amazon milk frog's anatomy. Image: ARTORG Center

    ARTORG Center for Biomedical Engineering Research, University of Bern; computed tomography of the Amazon milk frog (Trachycephalus resinifictrix).

    At the ARTORG Center, the research team analyzes the data from the computed tomography scanner. Photo: ARTORG Center

    Taking a look inside

    From Bern, the frog traveled back to Zoo Zurich. At the zoo's veterinary station, a pathologist from the University of Zurich dissected the dead animal, focusing on the leg and the turquoise bones inside. The project-leading researchers from the Paul Scherrer Institute and EPFL documented the process in detail.

    Amazon milk frog; dissection by pathologist Udo Hetzel (Zurich Animal Hospital); Marianne Liebi and Torne Tänzer (SPI Villigen).

    Back at the zoo, pathologist Dr. Udo Hetzel (University of Zurich) and Prof. Marianne Liebi and Torne Tänzer (Paul Scherrer Institute/EPFL) take a close look at the dead frog. Photo: Zoo Zurich, Nicole Schnyder

    The next stage will take the frog to the Paul Scherrer Institute. There, researchers will further analyze the leg bones with synchrotron light and study the nanostructure of the bone matter.

    Where from and what for?

    Researchers already know that the unusual bone color of the Amazon milk frog is due to an accumulation of «biliverdin» – a pigment produced during the breakdown of red blood cells. What's more complex to decipher is the question of how exactly it benefits the frog to have these blue bones. In order to find a conclusive answer to this question, several follow-up studies will be necessary in addition to the current study.