How Many Base Pairs Does it Take to Get the Centre of a Zebra Mussel

Invasive species are a topic close to my heart. They are the second leading cause of species extinction, only behind habitat destruction and fragmentation. As is if that is not enough of a cause to get behind, they also can have tremendous economic and social effects as well.

Considered one of the IUCN's World’s 100 worst invasive species and one species we are desperate to keep out of the western part of Canada are Zebra Mussels (Dreisenna polymorpha). Zebra mussels are native to the Caspian, Black and Aral Seas of Europe and gained real infamy after their detection in the North America’s Great Lakes in the 1980s. Transported via ballast water, ships from Europe travel up the St. Lawrence River and intro the Great Lakes, releasing their ballast full of larval mussels and the rest is history.

Zebra mussels, their effects and management cost billions of dollars annual in North America. Via their gregariousness, high reproductive output, and filter feeding capabilities, zebra mussels can heavily foul hydroelectric and water treatment infrastructure, compete with native biodiversity for food and space, render water bodies oligotrophic and unproductive, smell terrible when they decompose and cover beaches with razor sharp shells.

Luckily for us the development of new tools is allows the invasive species community of academics and managers to look for new ways to control and prevent invasive species. Traditionally, molecular tools like genetics have been used to look at population structure, distinguish invasives from congeners, infer vectors and origins of invasives and look for traits that could be used to predict invasiveness. Recently, scientist from the University of Michigan have completed sequencing the Zebra Mussel genome in the hopes that we can pinpoint the exact genes that have allowed the mussel to thrive and identify weaknesses that could be exploited to collapse mussel populations, slow or stop their spread.

“This was the first step,” said Nick Phelps, director of the U’s Minnesota Aquatic Invasive Species Research Center. “We don’t know yet quite where to attack. But now there’s a whole spectrum of strategies that can be considered.”

The Bivalves are a large class of Mollusca with over 10,000 described species in marine and freshwater environments. Surprisingly, invasive bivalves cause damage to aquatic ecosystems worldwide and to date there are only eight complete bivalve genomes out there. We won’t go into the methods, but to learn about genome assembly see the link here.

Recently published in bioRxiv the authors identified genes which encode a set of heat-shock and anti-apoptotic proteins (response to thermal stress) with are presumed to help with their sedentary lifestyle and genes linked to population growth and invasiveness (shell and byssal thread formation). Sequencing yielded a genome of 1.8Gb (gigabase pair); which was 1.3Gb larger than previously estimated; for comparison the human genome is 2.9 Gb.

How this new information is used to combat zebra mussels and their spread is exciting to think about. Strategies could include manipulating the genome which could help to slash their numbers by affecting their basic biology, induce die off or ways to improve conventional methods such as chemical control. However, it is important to note, the genetic manipulation would require likely years of vigorous testing and trials.

To read this exciting paper and gain access to the genome please see:

McCartney, M.A., Auch, B., Kono, T., Mallez, S., Zhang, Y., Obille, A., Becker, A., Abrahante, J.E., Garbe, J., Badalamenti, J.P. and Herman, A., 2019. The Genome of the Zebra Mussel, Dreissena polymorpha: A Resource for Invasive Species Research. BioRxiv, p.696732.