A new study into an ancient sea worm called Oesia offers clues about a common ancestor which they shared with vertebrates, including humans, while also showing that the worms inhabited tube-like “dwellings” on the sea bed.
The fossilised remnants of tube-like “dwellings” which housed a primitive type of prehistoric sea worm on the ocean floor have been identified in a new study.
According to researchers, the long, perforated tubes may have looked like narrow chimneys reaching up from the sea bed, and were made by a creature called Oesia, which lived a solitary existence inside them about 500 million years ago.
This image shows artist’s impression of Oesia inside a tube. *CREDIT: MARIANNE COLLINS
The findings emerge from a study undertaken by academics from Canada and the UK, in which they reassess fossils originally believed to have come from a type of seaweed called Margaretia. Instead, they found that these were the vestiges of tubular structures which protected these ancient worms.
Karma Nanglu, from the University of Toronto and the study’s lead author, said: “Hemichordates are central to our understanding of how deuterostomes evolved. Through them, we can get clues about the anatomy and lifestyle of the last common ancestor that we all share, and this adds further evidence to the hypothesis that the ancestor was a filter-feeder like Oesia.”
Part of its importance is that it confirms Oesia was a primitive specimen from a group of creatures called hemichordates. These belong to a bigger group called deuterostomes, of which vertebrates (including humans) form a separate branch. By finding out more about these early creatures, researchers hope eventually to be able to identify and characterise a distant ancestor common to all deuterostomes, from sea worms to humans.
In particular, the research supports the increasingly common view that this ancestor was probably a “filter feeder”, which ate by sucking in water and straining out nutrients. Oesia was one such filter feeder, with gills down most of its body to expel water afterwards, and holes in the walls of its tubular home to let the water in and out.
The researchers realised that Oesia must have lived in tubes because among the Marble Canyon finds there are dozens of examples where the fossil remains of the worm are found within those of Margaretia.
The research, which is published in the journal BMC Biology, was carried out by academics from the Universities of Cambridge, Toronto and Montréal, and at the Royal Ontario Museum in Toronto. Professor Simon Conway Morris, Dr. Jean-Bernard Caron, Christopher B. Cameron were co-author of this research.