Studies have confirmed several independent evolutions of the animal nervous system

Xenoturbella bocki
Photo Source: Ulf Jondelius
A study of some of the world's most hidden marine life shows that, as previously thought, the central nervous system has undergone several independent evolutions, not one.
the invertebrates discussed belong to families scattered throughout the animal evolutionary tree and exhibit diversity in the structure of the central nervous system. The creatures also activate genes involved in the development of other well-studied animal nervous systems, such as the bmp gene. However, the former did this in a non-neural way. The researchers report the
in the Journal of The New Year.
" provides clues to many of the questions we haven't answered, such as whether the central nervous system evolved independently in different branch systems and why they have so many similarities. Greg Wray, an evolutionary developmental biologist at Duke University in the United States, said.
to find organisms with diverse nervous systems, and Andreas Hejnol, an evolutionary and developmental biologist at the International Centre for Marine Molecular Biology in Norway, led a team that explored the fjords of Sweden and Norway by boat. They sifted through the sludge from the seabed and studied the intestines of seawater to look for parasites buried inside. Scientists also searched rocky shores of islands near Washington state.
the smallest worms collected by the team belong to an ancient branch of the animal evolutionary tree called Xenacoelomorpha and have a large nervous system. Xenoturbella bocki, for example, does not have a central nerve rope, but has a neural network similar to a jellyfish; Isodiametra pulchra has eight nerve ropes; and Meara stichopi, like vertebrates, has a nerve rope that extends along the back.
as in column worms, these very small worms activate the bmp gene early in embryonic development before nerve ropes are formed. What's more, Hejnol blocked the protein path, and then found that the animals' nerves were still developing. These results suggest that they build nerve ropes in a different way than mice, fruit flies, and other well-studied animals.
For wrist-footed animals, marine organisms named after their protective layer shapes, the Hejnol team found that other genes previously associated with central nerve ropes were activated as they developed, even though they did not have central nerves. This inseidity continues to exist in new worms and other strange animals.
Hejnol reasoned that genes associated with vertebrates, fruit flies, and some link animal central nerves worked in different ways in early ancestors and were fused into different parts of the nervous system as different animal branches evolved their own central nerves. (Source: Science Network Zonghua)