Bats’ Jaws Evolve In Wild Shapes, Sizes To Exploit Food Sources, Study Finds

(Photo : Getty Images/Jenny Evans)

Scientists have been attracted by the extraordinary evolution of noctilionoid bats, a diverse species of bat found largely in the American tropics.

Researchers probed into the interesting characteristics of over 200 species of noctilionoid bats, giving new information on the development of mammalian faces, notably jaws and teeth.

Evolution Of Bat's Jaw

A recent study published in Nature Communications shows that bats have considerable variations in jaw shape, size, tooth number, and tooth position, all of which are finely adjusted to exploit varied food sources.

Due to space limits, bats with shorter snouts, like bulldogs, have fewer teeth. Species with longer jaws, on the other hand, can accommodate more teeth, resembling the tooth count of placental mammals' ancestors.

Comparing noctilionoid species can offer a lot about how mammalian faces evolved and developed, notably jaws and teeth.

"Noctilionoid bats evolved a huge diversity of diets in as little as 25 million years, which is a very short amount of time for these adaptations to occur," said co-author Sharlene Santana, a University of Washington professor of biology and curator of mammals at the Burke Museum of Natural History & Culture.

Scientists are unsure what caused this flurry of dietary modifications in noctilionoid bats. However, different noctilionoid species now consume insects, fruit, nectar, fish, and even blood, as this group contains the iconic vampire bats.

The researchers examined the shapes and sizes of jaws, premolars, and molars in over 100 noctilionoid species using CT scans and other methods.

The bats comprised museum specimens as well as a small number of wild bats collected for research purposes.

The researchers studied the relative sizes of teeth and other cranial features in species with various diets and then used mathematical modeling to understand how such differences are formed throughout development.

The researchers discovered that particular "developmental rules" in noctilionoid bats caused them to grow the proper mix of teeth to fit in their diet-formed smiles.

Bats with lengthy jaws, such as nectar-feeders, or intermediate jaws, such as many insect-eaters, had the standard complement of three premolars and three molars on each side of the jaw. However, bats with short jaws, such as most fruit-eating bats, discard either the middle premolar or the back molar, if not both.

Further Study

Many studies on the development of mammalian teeth have been conducted in mice, which have just molars and severely modified incisors.

Scientists are unsure whether the genes and developmental pathways that influence tooth growth in mice also function in mammals with more "ancestral" sets of chompers, such as bats and humans.

"This project is giving us the opportunity to actually test some of the assumptions that have been made about how tooth growth, shape and size are regulated in mammals," said Santana. "We know surprisingly little about how these very important structures develop."

Experts seek to learn more about the genetic and developmental mechanisms that influence tooth growth in this varied group of bats by expanding their research to include noctilionoid incisors and canines.

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