CLEMSON – Modern day technology is helping a Clemson University professor and an international, interdisciplinary team of collaborators track the evolution of a beetle family by revealing a fossil’s internal anatomy.

Internal anatomy of the fossil, showing various organs. This is in the opposite orientation of the above pictures. Light blue tubes all over are the tracheae, the breathing tubes of the beetle. The small dark orange to the right (the head end) is the crop, where food passes through on the way to the gut. The large lighter orange to the left is the ‘hindgut’ more or less equal to the human large intestine. The yellow and purple are glands associated with the reproductive system. Red, darker blue and gray are the male genitalia.

Internal anatomy of the fossil, showing various organs. Light blue tubes are the tracheae, the breathing tubes of the beetle. The small dark orange to the right (the head end) is the crop, where food passes through on the way to the gut. The large lighter orange to the left is the “hindgut,” more or less equal to the human large intestine. The yellow and purple are glands associated with the reproductive system. Red, darker blue and gray are the male genitalia.
Image Credit: Thomas van de Kamp and Achim Schwermann

Michael Caterino, director of the Clemson University Arthropod Collection and Morse Chair of Arthropod Biodiversity at Clemson, and his colleagues from the University of Bonn, the Karlsruhe Institute of Technology (KIT), and the Stuttgart State Natural History Museum in Germany are using modern imaging techniques to look at the internal structure of 30-million-year-old beetles. According to Caterino, information the researchers obtain from extinct species can help them better reconstruct evolutionary patterns among modern species. The specimen being studied is a member of the family of beetles called Histeridae.

“The technique used revealed a very well-preserved internal anatomy of the specimen,” Caterino said. “Never has the inside of a Histerid looked so good.”

A particle accelerator at the Angstromquelle Karlsruhe (ANKA) Synchrotron Radiation Facility at KIT was used to analyze the fossils using X-ray computed tomography (micro-CT). This technique provides a detailed, 3-D image of the specimen, including both external and internal anatomy. The imaging shows mouthparts, gastrointestinal tract and the complex tracheal system, as well as reproductive organs.

“An analysis of the genealogical tree using these anatomical features clarified the kinship of the fossil beetle within clown beetles,” Caterino said.

Clown beetles are still in existence today. Using information gained from images produced by the micro-CT, researchers are better able to understand how different species have survived over time.

“For example, we can determine how much distributions, or where the insects lived, have changed,” Caterino said. “We also can tell how the insects have responded to changes in the environment. This gives us an unprecedented view of their history.”

The specimens studied, members of the species Onthophilus intermedius, come from a collection of of arthropods, mainly insects, from the Quercy region of France. Caterino and the other researchers have published their study in the prestigious online journal eLife. The article, titled “Preservation of three-dimensional anatomy in phosphatized fossil arthropods enriches evolutionary inference,” presents the first study on these fossils since their original description in 1944.

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