SciTech

Science Q & A: Did dinosaurs shed their skins?

Q. Did dinosaurs peel or shed their skins?

A. Presumably, said Mark A. Norell, chairman of the division of paleontology at the American Museum of Natural History. But not all at once.

“Since we can’t directly observe extinct animals, we need to look at close relatives,” Norell said. “Birds are living dinosaurs, crocodilians their closest relatives. Both shed skin in patches and strips, not entire skins like snakes.

“Because crocodiles and birds share a common ancestor, we predict this skin-shedding style was present in that ancestor. Non-bird dinosaurs descend from this same ancestor. Without other information, we predict that even giant dinosaurs exfoliated their dead, dry skin in patches.”

Everything that has skin sheds it, Norell emphasized, but there is a tremendous diversity in how skin sheds. In humans, for example, rubbing the dry skin of an arm across something black leaves a white scuff of dead skin cells, he said. And in birds, skin dries and sloughs off as small patches, like peeling after a bad sunburn.

Reptile shedding usually conjures visions of whole snakeskins, shed as a continuous piece, “looking like the ghost of a living serpent,” Norell said. But this is an exception; most animals do it differently. Typical reptiles – lizards, crocodiles and turtles – shed dry, irregular skin patches, and that is probably how dinosaurs did it, he said.

Water hot enough to kill germs?

Q. If you can put your hands in the water while washing dishes, is it really hot enough to kill germs? And if not, what’s the point of using all that energy?

A. The Food and Drug Administration code for dishwashing by hand in a commercial food establishment calls for a wash solution temperature of 110 degrees Fahrenheit, which is uncomfortably hot for hands but not hot enough to kill most germs.

The stated reasoning behind the relatively low temperature requirement for the washing stage of the three-part washing-rinsing-sanitizing standard is not direct germicidal action. Rather, according to the FDA, it is to make sure that the water is hot enough to remove organic matter from the dishes and to dissolve animal fats that may be present on them. A lower temperature might also interfere with the performance of the detergent being used, the guidelines state.

A study by food scientists at Ohio State University, published in June 2007 in The Journal of Food Engineering, found evidence that even lower temperatures may be effective at germ removal in many circumstances. For example, in a study of washing various kinds of soiled dishes purposely contaminated with bacteria, a temperature of only 75.2 degrees Fahrenheit reduced Escherichia coli and Listeria innocua to acceptable levels when all three steps were otherwise properly performed – except in the case of glasses with dried-on milk. Using a more concentrated sanitizing agent in the last step was also effective, the study found.

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