New research hints that comb jelly may be Earth's oldest animal
Scientists believe they may have identified the first animal to have roamed the Earth about 700 million years ago, a new study published in Nature revealed.
Researchers determined that the first animal was likely a comb jelly, or ctenophore — a predator that travels through the ocean in search of food, according to a news release about the study from the University of California Berkeley.
Though they resemble jellyfish, comb jellies are distinctly different creatures, and propel themselves through water using cilia instead of tentacles. They are still part of the marine ecosystem today and can be found in waters all over the world.
"The most recent common ancestor of all animals probably lived 600 or 700 million years ago. It's hard to know what they were like because they were soft-bodied animals and didn't leave a direct fossil record," said Daniel Rokhsar, a UC Berkeley professor and co-author of the study, in a statement. "But we can use comparisons across living animals to learn about our common ancestors."
There has long been a debate on which animal came first — the ctenophore or the sponge, the university said. Sponges are creatures that spend most of their lives in one spot, filtering water through their pores to collect food particles.
Many have argued that due to the sponge's primitive features, it came first — before the ctenophore, researchers said. This new research has determined that while sponges came early, they were likely second to ctenophores.
In order to make that determination, scientists looked at the organization of genes in the chromosomes of the organisms. The chromosomes of the ctenophore look very different than the chromosomes of sponges, jellyfish and other invertebrates — alerting researchers that the ctenophore could have either come much earlier than the others, or much later.
"At first, we couldn't tell if ctenophore chromosomes were different from those of other animals simply because they'd just changed a lot over hundreds of millions of years," Rokhsar explained in the news release. "Alternatively, they could be different because they branched off first, before all other animal lineages appeared. We needed to figure it out."
The "smoking gun" for researchers was when they compared the chromosomes of ctenophores to non-animals.
"When the team compared the chromosomes of these diverse animals and non-animals, they found that ctenophores and non-animals shared particular gene-chromosome combinations, while the chromosomes of sponges and other animals were rearranged in a distinctly different manner," the news release said.
According to researchers, the new insight is valuable to learning about the basic functions of all animals and humans today, such as how we eat, move and sense our surrounding environment.