Amazing sight in ancient sea creatures has led to an evolutionary arms race

According to new research released today, ancient deep-sea creatures called radiodonts had incredible vision that likely led to an evolutionary arms race.

The international study, led by Professor John Paterson of the Palaeoscience Research Center at the University of New England, in collaboration with the University of Adelaide, the South Australian Museum and the Natural History Museum (United Kingdom), has revealed that radiodonts have developed sophisticated eyes for 500 million years. there are, with some adapted to the low light of deep waters.

“Our study provides critical new information on the evolution of early marine animal ecosystems,” said Professor Paterson. “In particular, he supports the idea that vision played a crucial role during the Cambrian Explosion, a pivotal phase in history when most large groups of animals first appeared during a rapid burst of evolution over half a billion years ago. “

Radiodonts, meaning “radiating teeth,” are a group of arthropods that dominated the oceans around 500 million years ago. The many species share a similar body layout comprising a head with a pair of large, segmented appendages to capture prey, a circular mouth with jagged teeth, and a squid-like body. It now seems likely that some have lived at depths of up to 1,000 meters and developed large, complex eyes to make up for the lack of light in this extreme environment.

“When complex visual systems appeared, animals could sense their surroundings better,” explained Professor Paterson. “It may have fueled an evolving arms race between predators and prey. Once established, the vision became a driving force of evolution and helped shape the biodiversity and ecological interactions we see today.

Some of the earliest radiodont fossils discovered over a century ago were isolated body parts, and the earliest attempts at reconstruction resulted in “Frankenstein monsters”.

But in recent decades, many new discoveries – including entire radiodontier bodies – have provided a clearer picture of their anatomy, diversity, and possible lifestyles.

The co-author, Associate Professor Diego García-Bellido of the University of Adelaide and the South Australian Museum, said the rich fossil treasure of Emu Bay Shale on Kangaroo Island in South Australia in particular has helped build a clearer picture of Earth’s first animals.

“The Emu Bay Shale is the only place in the world that preserves eyes with Cambrian radiodont lenses. The more than thirty eye specimens we have now have shed new light on ecology, behavior. and the evolution of these largest living animals half a billion years ago, “A / Prof. Said García-Bellido.

In 2011, the team published two articles in the journal Nature on eyes composed of 513 million year old Emu Bay shale fossils on Kangaroo Island.

The first article on this topic documented isolated eye specimens up to one centimeter in diameter, but the team were unable to attribute them to a known arthropod species. The second article detailed the stalked eyes of Anomalocaris, a top predator up to one meter in length.

“Our new study identifies the owner of the eyes of our first article from 2011: ‘Anomalocaris’ briggsi – representing a new genus that has yet to be officially named,” said Professor Paterson.

“We have found much larger specimens of these eyes, up to four centimeters in diameter, which have a distinctive ‘sharp zone’, which is a region of enlarged lenses in the center of the eye’s surface that improves capture. and the resolution of light.

The large lenses of ‘Anomalocaris’ briggsi suggest that it could see deep in very low light, similar to amphipod crustaceans, a type of shrimp-like creature that exists today. The frilly thorns on its appendages filtered out the plankton it detected looking up.

Dr Greg Edgecombe, a researcher at the Natural History Museum in London and co-author of the study, added that the radio stations from South Australia show that the different feeding strategies previously indicated by the appendages – to capture or filter the prey – are parallel by differences in the eyes.

“The predator has eyes attached to the head on the stems, but the filter feeder has them on the surface of the head. The more we learn about these animals, the more diverse their body plan and ecology,” Dr. Edgecombe told me. said.

“The new samples also show how the eyes have changed as the animal has grown. Lenses formed at the margins of the eyes, enlarging and increasing in number in large specimens, just as in many living arthropods. for over 500 million years. ”