Preserved in 100-million-year-old amber, the confrontational interaction between extinct ant species indicates that advanced sociality in arthropods was present tens of millions of years earlier than previously thought.
The research, published in two papers in Cell Biology, was led by researchers from the American Museum of Natural History and the Univ. of Kansas. One study focuses on ants, while the other focuses on termites.
Prior to the discovery, researchers had postulated that eusociality first appeared during the Late Jurassic period, about 150-160 million years ago. However, the only physical evidence dated to between 17 and 20 million years ago during the Miocene.
“In the Cretaceous amber we examine, the ants and termites represent the earliest branches of each evolutionary tree, and the species are wildly different from what their modern relatives look like today,” said the studies’ co-author Phillip Barden.
Interestingly, many eusocial animals belong to the phylum Arthropoda. These animals share common characteristics, which include adults living in groups and cooperatively caring for juveniles, and reproductive specialization (placing individuals in castes).
“Whereas primitively eusocial organisms show no morphological difference between reproductive and non-reproductives, advanced eusocial organisms may have different morphologies for reproductive and non-reproductive individuals and even specialization within the non-reproductives,” according to entomologist Nicola Plowes, who is unaffiliated with the studies.
In the preserved ant specimens, the researchers discovered instances of social behaviors, including combat and worker recruitment, and the evidence of different castes.
Among the preserved termite specimens, researchers found six individual species. Within species, the researchers saw a diverse anatomy, indicating that castes were present. Two of the termite species studied were newly discovered, and the researchers named them Gigantotermes rex and Krishnatermes yoddha.
“These discoveries demonstrate the Mesozoic antiquity of specialized termite caste systems and corroborate that among all social species, termites probably had the original societies,” the researchers wrote in their study.