The key is in the whiskers or how mammal ancestors evolved #weekendusers

30-10-2017

Mammal’s ancestors evolved in size and appearance throught millions of years to avoid predators. Researchers from the University of Witswatersrand are on ID19 this weekend to find out whether whiskers played a role in this evolution.

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Therapsids were mammal-like reptiles, ancestors to today’s mammals, and evolved throughout time. They started off being diurnal animals, of around the size of a dog, some 270 million years ago. Then, with the uprising of the dinosaurs, around 190 million years ago, they became much smaller, around the size of mice, and became nocturnal as a way of surviving these huge predators. Their eyes became larger, the ears presumably more developed and they possibly grew whiskers to compensate their poor eyesight in the dark.

Paleontologist Julien Benoit and physicist Kudakwashe Jakata, both from the Evolutionary Studies Institute (University of Witswatersrand, Johannesburg, South Africa), together with Vincent Fernandez, scientist at the ESRF, are on beamline ID19 this weekend looking for the evidence of whiskers in 8 specimens brought straight from South Africa. Whiskers play a critical role in sensing the environment in mammals. Their sensitivity allows the animals to feel the presence of predators in the area even by just noticing the vibrations in the air. They also help them to move and orientate in the dark.

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Julien Benoit, Kudakwashe Jakarta and Vincent Fernandez (from left to right) in the control hutch of ID19. Credits: C. Argoud.

How do you study whiskers in 200 million years old fossils? There is a nerve, called the trigeminal nerve, which is responsilbe for the innervation of whiskers and facial sensitivity, and it is encapsulated in a bony canal, called the maxillary canal. In specimens with whiskers, the nerve should come out of the canal and ramifies inside the lips, whilst it stays enclosed in bone in those without whiskers. The nerve leaves a trace on the bone, and this is exactly what Benoit, Jakata and Fernandez are looking for using X-ray tomography.

“We had done some scans in our CT-scan lab in Johannesburg but we really need the capabilities of the synchrotron to find the evidence, especially in the smallest samples”, explains Benoit. Jakata, who is the manager of the CT-scan facility in the University of Witswatersrand, says coming here has been an eye-opening experience: “The images are really outstanding, I’ve been blown away by the resolution you get here. There is so much you can do here, it is a really formative experience”.

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Two moments of the experiment: setting up the sample (left) and arriving in the control room with the specimens. Credits: C. Argoud.

South Africa is a Scientific Associate of the ESRF at a level of 0.3%, funded the National Research Foundation (NRF), and, since the beginning of their membership the collaborations between the country and the ESRF have flourished, especially in the paleontology domain. “In South Africa we have wealth of fossils and the paleontology community is very strong. For years, we could only guess many of the features that they hide. But today this has changed thanks to synchrotron developments throughout the last decade. For paleontologists like me, being able to apply for beamtime is an unmissable opportunity that can lead to carry out experiments that I couldn’t do anywhere else”, says Benoit. “And hopefully we’ll shed light on the fascinating evolution of these mammals, and the origin of hair and warm-bloodedness”, he concludes. 

Text by Montserrat Capellas Espuny

Top image: The team in the experimental hutch with one of the samples. Credits: C. Argoud.