Scientists have long pondered the question of how complex animals evolved. A newfound worm species could help solve this major evolutionary puzzle of our time.
The worm, scientifically known as Xenoturbella, was found on the seafloor of the western Pacific Ocean. It is a strange creature with no brain, anus and kidneys. However, it contains a digestive system that has only one opening.
The worm is the part of Bilateria, a group that contains most complex animals including humans. So it could help explain the origin of a number of complicated internal body parts of the animals.
Researchers from University of Tsukuba in Japan have examined two specimens of Xenoturbella japonica found in the seafloor of Western Pacific. One is a female about 5 cm in length while the other is a juvenile about 1 cm long. Both are pale orange in color and have an oval shaped mouth. They constitute a new species of Xenoturbella.
CT scanning of the specimens have revealed their inner structure including a new feature called frontal pore that would otherwise not be identified.
"We also extracted DNA and sequenced the mitochondrial genome and partial Histone H3 gene sequences," said study co-author Hideyuki Miyazawa. “Molecular phylogenetic analysis confirmed that X. japonica is distinct from previously described species of Xenoturbella.”
Although the worm species is new to science, it is closely related to other groups of Xenoturbella and promises to hold valuable information about bilaterian evolution.
"Species within this genus have previously been divided into 'shallow' and 'deep' subgroups, and our results place X. japonica in the 'shallow' subgroup," said lead author Hiroaki Nakano. "Interestingly, X. japonica shares features with both subgroups, however. Thus, features of this species may be ancestral for this genus, and this new species may be particularly important for unraveling the ancestry of Xenoturbella and the early history of the Bilateria."
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