The strange new seafloor worm without an anus: Bizarre find could shed new light on how our internal organs evolved

Researchers discovered two specimens of the pale-orange worm in the Pacific
The new worm lacks a centralized nervous system, kidneys, and an anus
Experts say it could shed light on structures that emerged in complex animals

Published: 22:59 GMT, 18 December 2017 | Updated: 23:55 GMT, 18 December 2017

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Researchers in Japan have discovered a bizarre new species of worm that could shed light on the origin of animals' complex internal body parts.

The strange pale-orange creature dwells on the floor of the western Pacific Ocean, and lacks a number of features – including an anus.

Scientists say the species comes from a group of worms that holds a ‘controversial’ place in the tree of life, as a sister group of that which contains most complex animals.

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Researchers in Japan have discovered a bizarre new species of worm that could shed light on the origin of complex structures inside animals’ bodies. The strange pale-orange creature dwells on the floor of the western Pacific Ocean

THE STRANGE WORM

These creatures dwell hundreds or thousands of meters beneath the surface, making them difficult to study.

But, the researchers say the latest discovery could now offer a solution.

Xenoturbella japonica was found in the western Pacific, in a region easily accessible from marine stations.

It lacks a centralized nervous system, kidneys, and an anus.

Of the two found in the new study, a female was measured to be about 5cm long, while the juvenile is said to be just 1 cm.

Researchers say the worm could shed light on the origin of features seen in complex animals.

The new species found on the western Pacific seafloor lacks a centralized nervous system, kidneys, and an anus.

It’s called Xenoturbella japonica, adding to other marine worms in the genus Xenoturbella.

In a new study, the team described two specimens of the bizarre worm: a 5-centimeter-long female, and a 1-cm juvenile.

While they don’t have an anus, these creatures do have a mouth, implying that the digestive organ is ‘a sack rather than a tube,’ according to the researchers.

The team conducted microCT scans to reveal the inner workings of the worm, and its ‘frontal pore,’ which traditional methods are unable to capture.

‘We also extracted DNA and sequenced the mitochondrial genome and partial Histone H3 gene sequences,’ said co-author Hideyuki Miyazawa.

‘Molecular phylogenetic analysis confirmed that X. japonica is distinct from previously described species of Xenoturbella.’

According to the researchers, the new species may have links to the origins of the group Bilateria – which includes most complex animals.

‘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.

‘Interestinyl, X. japonica shares features with both subgroups, however.

The new species found on the western Pacific seafloor lacks a centralized nervous system, kidneys, and an anus. It’s called Xenoturbella japonica, adding to other marine worms in the genus Xenoturbella

In a new study, the team described two specimens of the bizarre worm: a 5-centimeter-long female, and a 1-cm juvenile

‘Thus, features of this species may be ancestral for this genus, and this new species may be particularly important for unravelling the ancestry of Xenoturbella and the early history of the Bilateria.’

These creatures dwell hundreds or thousands of meters beneath the surface, making them difficult to study.

But, the researchers say the latest discovery could now offer a solution.

According to co-author Hisanori Kohtsuka, ‘because one habitat where X. japonica was found is easily accessible from a marine station, this new species promises to be valuable for future research on bilaterian and deuterostome evolution.’

While they don’t have an anus, these creatures do have a mouth, implying that the digestive organ is ‘a sack rather than a tube,’ according to the researchers