Today’s spiders spend most of their time on land, moving in the fields, forests, deserts and almost all the other terrestrial habitats that exist. But that does not mean that their ancestors always lived terrestrial.
A new study in Current biology suggests that the arachnids – the group of arthropods which includes spiders, scorpions and their close relatives – could originally be residents of the ocean. Based on the brain and nervous structures finely preserved from a fossilized sea arthropod about 500 million years ago, the study shows that the first arachnids may have emerged in the oceans and then passed to land later.
“It is still vigorously debated where and when the arachnids appeared for the first time,” said Nicholas Strausfeld, study author and neuroscientist at the University of Arizona, in a statement. But the new research provides answers, suggesting that the ancestors of spiders and scorpions may have had a more humid start than what we traditionally thought.
Find out more: This arthropod of $ 444 million was fossilized backwards
An ancestor of sea spider?
Advanced imaging techniques have enabled the search team to identify the key anatomical characteristics of the fossilized remains of the Mollisonia specimenia. (Image credit: Nick Strausfeld)
Arachnids have existed for about 400 million years, and according to the fossil file, they seem to have spent most of this time on the ground. But what about the first arachnids? Are they emerged on water or on earth?
To answer this question, Strausfeld has taken a variety of photographs of a finely preserved fossil from Symmetrical softeningA marine arthropod of the Cambrian period, about 500 million years ago, in various conditions of lighting and magnifications. Separated in two segments, including a large shell at the front of his body and a trunk and a tail segmented at the back, the fossil species were traditionally considered as an iron -ironing ancestor today.
But by revealing the fossilized traces of the specimen nervous system, the photographs illustrate that SoftenThe brain and nerves were placed less like those of a modern horseshoe crab and more like those of a spider or a modern scorpion, instead.
According to their analysis, Strausfeld and his co-authors suggest that the species was probably an ancestor of the first arachnids, which implies that spiders and scorpions came from a marine arthropod, rather than land.
Find out more: A new arthropod of 450 million 450 million has been kept in the gold of the madman
Origins of the back brain
A comparison side by side of the brain of a horseshoe crab (on the left), the Mollisonia fossil (center) and a modern spider (on the right) reveals the surprising results of this study: the organization of the three brain regions of Mollisonia (green, magenta and blue) are reversed compared to the horseshoe crab, and rather resemble the arrangement found in modern episodes. (Image credit: Nick Strausfeld)
So what was it Soften Nervous system which indicated that it was a parent of the spiders and scorpions today?
First of all, Soften had a network of radiant nerves which controlled the movement of its multiple appendages, much like the network of radiant nerves in the arachnids today. Second, Soften had a series of short nerves which controlled his pair of “claws” facing forward, similar to the nerves of modern arachnids, which control their own pairs of fangs and pliers. Third, SoftenThe brain had an inverted structure, which was not organized from front to back, as in horseshoe crabs, but from back to front, as in spiders, scorpions and other arachnids.
Strausfeld and his co-authors say that this back arrangement may have been very advantageous for the first arachnids, shortening the distance between their neural control centers and their nerves. In fact, this configuration could have helped them with their speed, stealth and agility, allowing the first arachnids to exercise impressive control over their own movement which is still seen in spiders and scorpions today.
“The arachnid brain does not look like any other brain of this planet,” said Strausfeld in the press release. “This suggests that its organization has something to do with calculation speed and control of motor actions.”
Find out more: Scientists find fossilized brains in arthropods aged 500 million
Hope for future fossils
Of course, the similarities between the Soften The nervous system and the arachnid nervous system could represent nothing more than just coincidence. Thus, to confirm that they were the result of a common ancestry, the researchers carried out a statistical analysis of 115 neuronal lines of species through the genealogical tree of arthropods. Their analysis has corroborated that Soften was closely linked to the first arachnids, supporting the theory that the species was an ancestor of modern spiders and scorpions.
Similar specimens can help researchers trace more from the evolutionary history of arachnids in the future. Although it is rare to find specimens with finely preserved nervous systems, hope is that other species love Soften Could show how the different arthropod lines have led to different arachnids that skitter on the ground today.
Sources of articles
Our writers at Discovermagazine.com Use studies evaluated by high -quality peers and sources for our articles, and our publishers examine scientific precision and editorial standards. Review the sources used below for this article:
Sam Walters is a journalist covering archeology, paleontology, ecology and the evolution of Discover, as well as an assortment of other subjects. Before joining the Discover team as a deputy editor in 2022, Sam studied journalism at the Northwestern University in Evanston, Illinois.
