Photo by Bernard Picton. Leptochiton asellsu in Loch Melfort, Scotland
A UCD scientist is unravelling the secrets of deep-ocean creatures by peering right into their DNA. Primitive molluscs called ‘leptochitons’ have changed little in outward appearance for million of years, but museum collections researcher Julia Sigwart has discovered remarkable genetic variation between species. Her research is refining our understanding of these living fossils, and will help biodiversity researchers to identify the animals in the wild.
“If we look at all the chiton fossils over the last 400-500 million years we see all kinds of dead ends. Then about 60 million years ago, something evolved that hit this Leptochiton form and it didn’t change,” says Sigwart, of the UCD School of Biology and Environmental Science.
Today many of the 120 known leptochiton species live around 1km under the ocean’s surface and are grouped into the same broad category. But Sigwart is breaking new ground by comparing DNA sequences from different species to identify more subtle relationships within the group.
“An important test of any kind of species group’s identity is to find out whether all of them are related to each other. What the DNA will help us to do is differentiate them into smaller groups that will let us give them characters that say it belongs in this genus rather than all in the one pot. It’s also very important in terms of looking at the evolution of molluscs as a whole,” says Sigwart.
So far she has profiled around 75 leptochiton species from all over the world and found substantial differences in key regions of their genetic codes. And as she untangles the evolutionary relationships, she will also look for useful external characters to help scientists to more accurately identify the animals in the wild: “I can tell other people: when you haul up a bucket of those you want to count the spines on the left side because that works.”
Research collaborator – Prof. Gonzalo Giribet at Harvard University
