You are inconspicuous; you go as far as being half buried to go unnoticed. Despite the unassuming and eerie flow, you are being stalked. You appear as meek prey; you are an easy target. Or are you…? You have adapted a lure. Appearing meek and vulnerable gives you an advantage. Lurking predators hope to ambush you, but you are a skilled deceptor. You are waiting for your stalker to strike, luring them in, so you can strike back!

Forget the haunting stalker and prey metaphor for a minute (don’t worry we’ll get back to it). In this spooky Forest for the Bats article, let’s break down freshwater mussels!

hands cupping multiple mussels

Photo courtesy of the Chesapeake Bay Foundation

North America is home to nearly 300 unique species of freshwater mussels. Southeastern states (home to nearly 200 freshwater mussel species), particularly those with tributaries flowing to the Mississippi River, host a massive hotspot of freshwater mussel species diversity. Even though the Chesapeake Bay region doesn’t contain the same abundance of mussel diversity as the southeast it is still undoubtedly an invaluable habitat for many Northern Atlantic species. The Chesapeake Bay region in the state of Virginia is home to 19 different freshwater mussels species; the Bay region in the state of Pennsylvania is reported to host around 12 freshwater mussel species; the Bay region in Maryland hosts 16 different mussel species.

So you may be wondering, what is a self proclaimed plant ecologist doing writing about mollusks? And why is she talking about bivalves in a Halloween themed newsletter? Well, because mussels are seriously wicked! And, because the imperiled fate of freshwater mussel species is legitimately scary.

Let’s discuss how wicked (wicked-cool) mussels in the Chesapeake Bay region and beyond are! Freshwater mussels provide extraordinary ecosystem services. Freshwater mussels have the incredible ability to filter massive amounts of water. This is a function for feeding (freshwater mussels can be omnivorous, as diet varies based on habitat and food availability), but allows for removing sediment, bacteria, viruses (including the avian influenza), pharmaceuticals, and other particles from the water column; the capacity of these processes increases in mussel beds, or areas with large numbers of living mussels. Beyond the water quality improvements freshwater mussel biofiltration provides, freshwater mussels support nutrient cycling and storage, create habitat, support food webs, and provide cultural value.

So let’s get back to this stalker and prey metaphor that I used to lure you into this article. Freshwater mussels have a 400-million-year-old phenomenon we call mantle lures, that have evolved to complete a fresh water mussels reproductive cycle. When a female freshwater mussel is ready to release her young after breeding, trickery and imitation ensues. A female mussel will open her shell and release appendages from her mantle that mimic prey; the lure may appear as a crayfish, an insect, any number of small fish or any other bait that may entice a fish. The mantle lure will appear vulnerable, but is really a loaded imposter, seeking and requiring the stalker. As each freshwater mussel is unique, they have a unique host fish that the female mussel aims to draw in. As the stalker approaches the mantle lure, oftentimes ending up sandwiched in the bivalve momentarily, the female mussel will release an explosion of glochidia (larval mussels) into the fishes mouth and gills. The glochidia leach onto the host fish, requiring its movement and blood to mature. Glochidia will maintain contact with the fish for a few months before dropping into the river bed. Freshwater mussels are eerie; they hunt their hunter, and their young are essentially vampires…

Photo courtesy of The Ohio River Foundation

If you aren’t already lured in, get ready to be. Freshwater mussels are one of the most imperiled groups of organisms on the planet. It is reported that 65-75% of freshwater mussels are facing listing status or are already extinct. It is predicted that watersheds worldwide will lose approximately 50% of remaining species within the next century. Even more devastating, species that were once more prolific, will face serious reduction in biomass and abundance. Why is this occurring you may ask? Well, humans… The construction of dams, and other habitat fragmentation practices such as steam channelization, ditching, dredging, separate mussels from their fish host, and cause sedimentation or siltation stress and impoundments. The introduction of invasive species, poaching or unethical harvest and so many other anthropocentric factors are at play here. A reminder, freshwater mussels are stationary, they cannot escape catastrophic events.

Photo courtesy of Michigan State University Extension

So, we’ve got this really awesome group of organisms that provides many invaluable ecosystem services, and is sort of like a freshwater vampire. Consider donating or volunteering at a local watershed organization, invertebrate society or mollusk research group this Halloween to increase your advocacy for these inconspicuous freshwater organisms.