Man holding collection of mussels

The Mollusk and Crustacean Collection

Learn how the collection helps Sean Keogh's research.

Published03/22/2021 , by Nehwoen Luogon-Bojkov

Man holding a collection of musselsState and federal agencies like the Minnesota DNR and the U.S. Fish and Wildlife Service regularly visit the mollusk and crustacean collection at the Bell Museum. When these visits occur today, they are full circle moments for Sean Keogh, who worked at the Minnesota DNR before his current role with the collection. It was with the DNR that he discovered his love and interest for freshwater mussels.

As an undergraduate student, Sean enjoyed spending his free time in the water and had a particular love for scuba diving. He had an early interest in natural resources but was still unsure of where he wanted to focus his studies. After spending time on a natural resources job forum, Sean realized he wanted to find a way to incorporate his love for scuba diving and natural resources into a profession. Through his search, he discovered a job posting with the Minnesota DNR that required a certified scuba diver. While he knew nothing about freshwater mussels at the time, the position met one of his major criteria for work—scuba diving! Sean got the job as a technician and worked for the DNR for three years. During that time, his supervisor’s infectious passion about his own work inspired Sean to advance in the same field.

Sean got the opportunity to help curate the mollusk and crustacean collection and began working in collections as a graduate student in Dr. Andrew Simons’ lab. Sean was studying the Yellow Sandshell species and noticed there were other shells in the collection that were larger. Right away, he was intrigued by the difference between the two shells and wondered—were they really the same species?

The desire to answer this question was further encouraged when Sean’s old supervisor at the Minnesota DNR, Bernard Sietman, visited the lab and suggested Sean conduct some genetic analysis. Once he began to dig deeper, Sean discovered that the two shells were not even closely related. There was a new species sitting in the collection just waiting to be studied! Sean wrapped up his research on this new species in 2019 and as a nod to his former supervisor, named the new species after him. The Bell Museum’s mollusk and crustaceans collection continues to be a great resource for Sean’s current work. By scanning shells from the collection, Sean is able to take digital morphology measurements. As he moved on to his doctoral work, Sean uses the Bell Museum freshwater mussel collections to find out how shell shapes change in different habitats across species. Sean is currently exploring making shell models using the collection to investigate the functional basis of shell shape in artificial streams at the St. Anthony Falls Laboratory.

While mollusks and crustaceans are often overlooked, Sean is eager to share how amazing these animals are—even if they are underappreciated. An interesting aspect of mussels is their interdependent relationship with freshwater fish. During the larval stage, the freshwater mussels attach themselves to a host fish. The host will then unknowingly transport the mussel larvae to various habitats, helping them spread across the landscape. Selecting a host fish is not an easy task! But the mussels have developed a strategy for attracting the right host. Some species have a lure that looks like a crayfish to attract largemouth bass or other species. This lure then clamps down on the host fish for the mussels to release their larvae onto the chosen host. One of the species in the collection attracts logperch. When the fish flips over this particular mussel that looks like a stone, it then releases its glochidia, parasitic larvae.

Sean is also trying to understand the mechanisms producing shell shape variation within species. The Giant Floater is a locally abundant species that occurs in both lakes and streams. In lakes, the species has an inflated, almost beach ball-like shell shape. But when it resides in streams, the shell takes on a much more streamlined shape. His research is taking a closer look to find out if this change is due to the environment or due to genetics. To study this, a mother mussel with glochidia was collected and taken to the DNR lab to be placed on other fish.  Once those fish began producing juvenile mussels, these were taken to the Minnesota Zoo and reared in an artificial pond. About 6,000 of these mussels were marked, then separated into eight different habitats (half lake and half stream sites). In a couple summers, the mussels will be recollected and shell shape will be measured to determine if differences are due to habitat type or genetics. Sean’s work with the mussels at the Minnesota Zoo will be added to the mollusk and crustaceans collection in the future.