Every living thing on Earth is able to adapt and survive, or end up dead. In a world that is constantly changing and challenging, this one three-eyed animal has become the most long-lived species.
In November 2010, Guinness World Records gave the title of "oldest living creature" to Triops cancriformis, a three-eyed animal often called a crayfish.
This coronation is supported by a good reason. Fossils show that these armored shrimp-like crustaceans have been around since the Triassic period, around 251.9 million to 201.3 million years ago.
Triops have a body shaped like a shovel. This body shape is very suitable for digging the bottom of the pond where they live. Their body design works so well that they can survive for hundreds of millions of years.
Although its appearance seems to have never changed, a DNA study published in 2010 revealed that the kecebong shrimp never stopped evolving behind its shell. It creates differences between species throughout time that are not always visible to the human eye.
For example, the crayfish T. cancriformis is only a descendant of Triassic ancestors that look similar and are actually no more than 25 million years old.
Three-eyed animal competitor
In addition to the kecebong shrimp, there is another "living fossil" that is its competitor in terms of survival, namely a group of deep sea fish called coelacanth.
Researchers first found coelacanth fossils in the 1800s and thought they went extinct at the end of the Cretaceous period 66 million years ago. But then, in 1938, fishermen hauled a live coelacanth off the coast of South Africa. This ancient fish is more than 400 million years old.
However, the coelacanth species that swim in our oceans today are not the same as the fossilized coelacanth species, which are truly extinct.
A 2010 study published in the journal Marine Biology estimated that living species of this type appeared in the last 20 million to 30 million years.
The same thing happened to the lineage of the ancient horseshoe crab that lived around 480 million years ago. A 2012 study published in the journal Molecular Phylogenetics and Evolution found that the oldest group of Asian horseshoe crabs called Tachypleus only appeared about 25 million years ago, despite looking similar to fossils that are hundreds of millions of years old.
Biologists have not finished unraveling the evolutionary history of all living animals and there will be no definitive answer to this mystery until they do. However, the three-eyed shrimp, coelacanth, and horseshoe crab all tell us that even the seemingly most stable organisms are always changing.
"I don't think there is any evidence that a single species has existed for more than a few million years," said Africa Gómez, an evolutionary biologist at the University of Hull and senior author of a 2013 crayfish study, quoted by Live Science.
Studies of the fossil record show that species usually last between 500 thousand years to 3 million years before they die due to extinction or are replaced by their descendants.
For example, an organism's DNA can mutate, and this mutation can be passed down from one generation to the next. Two genetically similar species can also mate, producing a new hybrid species that thrives. Competition also forces species to evolve. Predators compete with prey, and animals that share the same space compete for food and resources.
"Predators evolve, prey evolves, predators evolve, prey evolves, competitors evolve, other competitors evolve," said Scott Lidgard, curator emeritus of invertebrate fossils at the Field Museum in Chicago.
Moreover, environmental factors can affect how long animals survive. "Say a group of taxa is well adapted to a certain type of habitat and the climate changes dramatically. If it can't migrate to another place with the same habitat, it will become extinct," said Lidgard.
Because change is constant, Gómez does not consider any animal to be a living fossil because the term implies that animals stop evolving. Instead, Lidgard argued that "living fossils" can be used as a general term to study organisms with certain attributes, such as a slow rate of evolutionary change.