Earliest Evidence Of Brood Care Revealed In 508 Million-Year-Old Fossils

A 508 million-year-old shrimp-like fossil named "Waptia" from the Canadian Burgess Shale fossil deposit represents the earliest-known evidence of brood care, a new study says. Waptia was originally found a century ago, but when researchers from the University of Toronto took another look at the remains they uncovered something interesting: embryos with eggs preserved in the animal's body. 

"As the oldest direct evidence of a creature caring for its offspring, the discovery adds another piece to our understanding of brood care practices during the Cambrian Explosion, a period of rapid evolutionary development when most major animal groups appear in the fossil record," Jean-Bernard Caron, curator of invertebrate paleontology at the Royal Ontario Museum and associate professor in the Departments of Earth Sciences and Ecology and Evolutionary Biology at the University of Toronto, said in a news release.

This brood-caring critter, scientifically known as Waptia fieldensis, was an early arthropod, belonging to the same group as lobsters and crayfish. Researchers say it had a two-part structure -- a bivalved carapace, or hard shell -- covering the front segment of its body, which would have played a key role in the animal's ability to carry its eggs. 

"Clusters of egg-shaped objects are evident in five of the many specimens we observed, all located on the underside of the carapace and alongside the anterior third of the body," Caron added in the university's release. 

These clusters are grouped in single layers on either side of its body, and researchers believe each animal could have carried a maximum of 24 eggs. 

"This creature is expanding our perspective on the diversification of brood care in early arthropods," Jean Vannier, co-author from the National Center for Scientific Research, said in the release. "The relatively large size of the eggs and the small number of them, contrasts with the high number of small eggs found previously in another bivalved arthropod known as Kunmingella douvillei. And though that creature predates Waptia by about seven million years, none of its eggs contained embryos."

Furthermore, researchers explained Kunmingella douvillei carried its young in a different way, where its eggs were found lower on its back, attached to its appendages, instead. These differing brood parenting styles shed light on the diversity of early arthropods and how the animals evolved independent ways for caring for their young. 

Their findings were recently published in the journal Current Biology.

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