The fossilised eyes of a 160-million-year-old crustacean show that the creature had complex eyes, which resemble those of modern arthropods (a group that includes insects, arachnids, myriapods, and crustaceans), a new study finds.
Dollocaris ingens, an ancient marine arthropod, probably used its complex vision to hunt as an ambush predator, according to the researchers. The animal was also equipped with grasping legs.
Jean Vannier, lead researcher of the study and a paleobiologist at the French National Center for Scientific Research in Lyon, said that the newfound creature is quite odd. Remains of undigested shrimp were found in its stomach, Vannier added.
Complex sight is thought to have evolved during the Cambrian period (between 541 million and 485.4 million years ago). Better vision was a game changer for many of the organisms that lived back then.
According to Vannier, things changed significantly once vision appeared. Prey was detected more easily by animals with eyes.
Fossilised eyes with sensory cells from the Cambrian period have yet to be found, which is why for the new study – published online Tuesday (Jan. 19) in the journal Nature Communications – the researchers looked at the Dollocaris ingens fossils that date back to the Jurassic period.
Although the fossils were found in the 1980s in the La Voulte-sur-Rhone formation in southeast France, they had not been thoroughly looked at until now, Vannier said.
The animal, which belongs to an extinct group of crustaceans called thylacocephalans, is about two to eight inches (five and twenty centimetres) long. Researchers discovered Dollocaris ingens’ exceptionally well-preserved eyes while they were studying the creature.
To look at Dollocaris ingens’ internal organs, Vannier and his colleagues used a technique known as X-ray microtomography, in which a virtual 3D model is created with X-ray cross-section scans. With a scanning electron microscope, they then found the intricate eyes.
Each eye has approximately 18,000 units called ommatidia – which contain clusters of photoreceptor cells surrounded by pigment cells and support cells – and they make up about twenty-five percent of the animal’s entire body. The only other modern arthropod that has more of these ommatidia is the dragonfly, with nearly 30,000.
Vannier and his colleagues said that the shape, size, and number of the ommatidia suggest that Dollocaris ingens had exceptionally sharp vision – a trait that is usually found in predators, like mantis shrimps and dragonflies.
Image Source: hirportal.sikerado.hu