Nav: Home

Early worm lost lower limbs for tube-dwelling lifestyle

February 27, 2020

Scientists have discovered the earliest known example of an animal evolving to lose body parts it no longer needed.

Mystery has long surrounded the evolution of Facivermis, a worm-like creature that lived approximately 518 million years ago in the Cambrian period.

It had a long body and five pairs of spiny arms near its head, leading to suggestions it might be a "missing link" between legless cycloneuralian worms and a group of fossil animals called "lobopodians", which had paired limbs all along their bodies.

But the new study - by the University of Exeter, Yunnan University and the Natural History Museum - reveals Facivermis was itself a lobopodian that lived a tube-dwelling lifestyle anchored on the sea floor, and so evolved to lose its lower limbs.

"A key piece of evidence was a fossil in which the lower portion of a Facivermis was surrounded by a tube," said lead author Richard Howard.

"We don't know the nature of the tube itself, but it shows the lower portion of the worm was anchored inside by a swollen rear end.

"Living like this, its lower limbs would not have been useful, and over time the species ceased to have them.

"Most of its relatives had three to nine sets of lower legs for walking, but our findings suggest Facivermis remained in place and used its upper limbs to filter food from the water.

"This is the earliest known example of 'secondary loss' - seen today in cases such as the loss of legs in snakes."

The Cambrian period is seen as the dawn of animal life, and the researchers were fascinated to find a species evolving to be "more primitive" even at this early stage of evolution.

"We generally view organisms evolving from simple to more complex body plans, but occasionally we see the opposite occurring," said senior author Dr Xiaoya Ma.

"What excited us in this study is that even at this early stage of animal evolution, secondary-loss modifications - and in this case, reverting 'back' to lose some of its legs - had already occurred.

"We've known about this species for about 30 years, but it's only now that we've got a confident grasp of where it fits in the evolutionary tree.

"Studies like this help us understand the shape of the tree of life and figure out where the adaptations and body parts we now see have come from."

Co-author Greg Edgecombe, of the Natural History Museum, said: "For several years we and others have been finding lobopodians from the Cambrian period with pairs of appendages along the length of the body - long, grasping ones in the front, and shorter, clawed ones in the back.

"But Facivermis takes this to the extreme, by completely reducing the posterior batch."

The Chengjiang Biota in Yunnan Province, south-west China has been a source of well-preserved Facivermis fossils.

Using these fossils, the study placed Facivermis in the Cambrian lobopodian group, which gave rise to three modern animal groups (phyla): Arthropoda (including insects, shrimps and spiders), Tardigrada (water bears) and Onychophora (velvet worms).
-end-
The research was funded by the Natural History Museum and the Natural Environment Research Council (NERC).

The paper, published in the journal Current Biology, is entitled: "A Tube-Dwelling Early Cambrian Lobopodian."

University of Exeter

Related Science Articles:

75 science societies urge the education department to base Title IX sexual harassment regulations on evidence and science
The American Educational Research Association (AERA) and the American Association for the Advancement of Science (AAAS) today led 75 scientific societies in submitting comments on the US Department of Education's proposed changes to Title IX regulations.
Science/Science Careers' survey ranks top biotech, biopharma, and pharma employers
The Science and Science Careers' 2018 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Science in the palm of your hand: How citizen science transforms passive learners
Citizen science projects can engage even children who previously were not interested in science.
Applied science may yield more translational research publications than basic science
While translational research can happen at any stage of the research process, a recent investigation of behavioral and social science research awards granted by the NIH between 2008 and 2014 revealed that applied science yielded a higher volume of translational research publications than basic science, according to a study published May 9, 2018 in the open-access journal PLOS ONE by Xueying Han from the Science and Technology Policy Institute, USA, and colleagues.
Prominent academics, including Salk's Thomas Albright, call for more science in forensic science
Six scientists who recently served on the National Commission on Forensic Science are calling on the scientific community at large to advocate for increased research and financial support of forensic science as well as the introduction of empirical testing requirements to ensure the validity of outcomes.
World Science Forum 2017 Jordan issues Science for Peace Declaration
On behalf of the coordinating organizations responsible for delivering the World Science Forum Jordan, the concluding Science for Peace Declaration issued at the Dead Sea represents a global call for action to science and society to build a future that promises greater equality, security and opportunity for all, and in which science plays an increasingly prominent role as an enabler of fair and sustainable development.
PETA science group promotes animal-free science at society of toxicology conference
The PETA International Science Consortium Ltd. is presenting two posters on animal-free methods for testing inhalation toxicity at the 56th annual Society of Toxicology (SOT) meeting March 12 to 16, 2017, in Baltimore, Maryland.
Citizen Science in the Digital Age: Rhetoric, Science and Public Engagement
James Wynn's timely investigation highlights scientific studies grounded in publicly gathered data and probes the rhetoric these studies employ.
Science/Science Careers' survey ranks top biotech, pharma, and biopharma employers
The Science and Science Careers' 2016 annual Top Employers Survey polled employees in the biotechnology, biopharmaceutical, pharmaceutical, and related industries to determine the 20 best employers in these industries as well as their driving characteristics.
Three natural science professors win TJ Park Science Fellowship
Professor Jung-Min Kee (Department of Chemistry, UNIST), Professor Kyudong Choi (Department of Mathematical Sciences, UNIST), and Professor Kwanpyo Kim (Department of Physics, UNIST) are the recipients of the Cheong-Am (TJ Park) Science Fellowship of the year 2016.
More Science News and Science Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.