Keeping an eye on freshwater mussels

December 3, 2018

Freshwater mussels

Spending their life either buried in the mud of river, lake, and pond beds, or as tiny young attached to fish, freshwater mussels can easily go unnoticed. Dr. Ryan Prosser and his research team at the University of Guelph’s School of Environmental Sciences however, are hoping to draw attention to these amazing organisms and the challenges they face in Ontario and throughout North America.

All freshwater mussels start life as parasites living attached to fish in most cases, or to salamander for a minority of species. The young are transmitted to the host by the female who has evolved clever ways of attracting or trapping fish. Some species such as the wavyrayed lampmussel (Lampsilis fasciola) and pocketbook mussel (Lampsilis cardium; see above photo), are equipped with an appendage that mimics a minnow and serves to lure unsuspecting predator fish close to the female mussel, at which point she releases her parasitic offspring. Other species, such as the snuffbox (Epioblasma triquetra) and northern riffle shell (Epioblasma torulosa rangiana), lack a minnow lure and instead will close their shell onto a fish’s snout as it is foraging in the sediment and will release their young while the host is thus trapped.

In addition to these truly fascinating reproductive behaviours and strategies, their lifespan is just as impressive - species in Ontario can typically live to be about 20 to 25 years old with some species living as long as 70 years. Freshwater mussels are also “ecosystem engineers”, filtering large volumes of water and removing algae and bacteria which results in clearer water for other aquatic species.

Dr. Prosser recognizes the value and significance of freshwater mussels and, along with his team, is working to protect them. In the fall of 2017, shortly after Dr. Prosser was appointed Assistant Professor in Environmental Toxicology at the University of Guelph, he initiated a project in conjunction with Environment Canada and Climate Change to develop a new method for monitoring freshwater mussels. There are approximately 40 species in Ontario, however about half are listed as endangered or threatened. On a broader scale, North America is home to an abundance of species which Dr. Prosser likens to being “the Amazon for freshwater mussels”, however many are also endangered.

The freshwater mussel monitoring project aims to develop a method for evaluating stress in mussels by drawing a small volume of hemolymph (mussel blood) from the muscle that opens and closes the shell and then measuring various metabolites. “Similar to when you go to the doctor and they’ll take a blood sample to look at for example, sugars or creatine, in order to help assess your health, we’re considering a similar approach to understand stress in wild mussels”, explains Dr. Prosser. Initial steps in developing the method involves rearing freshwater mussels in the lab and testing various stressors that are known to impact wild populations.  Exposure to chloride from road salts is an important stressor as well as exposure to some insecticides used in agriculture.

Given that assessing freshwater mussel populations is very labour intensive and difficult since juveniles and adults are hard to detect, this new monitoring method will help determine if individuals in a population are under stress. Environmental managers and conservation biologists can then use this information to do what is necessary to rectify a problem before population and species numbers decline to dangerously low numbers or disappear from waterbodies altogether.