Evrim Yazgin
Cosmos science journalist
Palaeontologists studying fossils of corals and algae from 385 million years ago have found a symbiotic relationship between the organisms today was present in the ancient past as well.
Photosynthetic algae recycle nutrients and are important for corals living in nutrient-poor waters.
Research published in Nature shows that this relationship was around nearly 400 million years ago during the Devonian period (419–589 million years ago).
The team analysed fossils of 2 extinct groups of coral: tabulate and rugose.
They looked at the levels of nitrogen isotopes in the coral fossils. This, they argue, can tell them whether the corals derived their energy from photosynthetic symbionts or not.
The findings revealed that the ancient tabulate coral did have symbionts, while the rugose coral did not. “These findings provide conclusive geochemical evidence of the earliest known example of symbiosis in corals,” the authors write.
Today’s corals did not evolve from these types of ancient coral. Modern corals all belong to a group called scleractinians which evolved in the Triassic period about 250 million years ago.
The research does reveal, however, the complex interactions and symbiotic relationships between species which existed nearly 400 million years ago.
“The evolutionary history of this symbiosis might clarify its organismal and environmental roles, but its prevalence through time, and across taxa, morphologies and oceanic settings, is currently unclear,” the authors say.
