Ancestors of vertebrates did not have a brain
discovery of a new phylum has revealed that human beings and other vertebrates had a common ancestor that did not have a brain. The genetic analysis of this half-inch long organism called Xenoturbulla, with no gonads, gut or brain, found deep in the North Atlantic, shows that it is a new phylum and not a mollusk as was earlier thought. The study was published online in the Journal Nature on November 2.
Analysis of 1,300 genes including mitochondrial genes by scientists at the Whitney Laboratory for Marine Bioscience, revealed that Xenoturbella belongs to its own phylum. Phyla represent the largest accepted group of animals used in the scientific classification of life. There are 35 phyla of which nine include majority of species. These are mollusca, porifera, cnidaria, platyhelmenthes, nematoda, annelida, arthropoda, echinodermata, chordata and cycliophora.
The study of Xenoturbulla, first spotted in the Baltic Sea more than 50 years ago, with its extreme characteristics point towards a common ancestor for echinoderms and hemichordates as well as chordates that did not have a brain or central nervous system.
Early genetic research identified it as a type of mollusk. But scientists discovered that the mollusk-like dna actually resulted not from the creature itself but from its close association to clams and its habit of feeding on mollusk eggs, said Leonid Moroz, a professor of neuroscience and zoology and a co-researcher.
"It's a tremendous surprise that this mysterious creature from the ocean will help us understand our distant past,' Moroz remarked. "It is a basal organism, which by chance preserved the basal characteristics present in our common ancestor. This shows that our common ancestor didn't have a brain but rather a diffuse neural system in the animal's surface.'