Freshwater Mussels: The Livers of the River

The creek was up and it ran murky and arduous. I didn’t anticipate to see a lot. It has been a summer season of episodic heavy rains which are likely to put a whole lot of mud in water and makes our streams run silty. 

I’m a freshwater snorkeler so I do what I at all times do: I caught my face in anyway. 

I’ve been fooled by floor appearances earlier than.  There’s normally an incredible world simply beneath the floor.

The swift present tried to peel me from the underside so I dug my fingers and toes additional into the cobble. Minnows fed within the slick of fabric I inadvertently churned up. I couldn’t see far more than haze, like trying by a fogged windshield.  I may make out shapes, and colours stood out.

A small faculty of rosyfaced shiners frantically snatched bugs I flushed off the underside.  However I didn’t see a lot else.  I held in opposition to the present for some time, till my arms began to twitch like stitching machines.

Bracing in opposition to move like that is like holding a steady plank, and my muscular tissues can solely final so lengthy earlier than they fatigue. Even when I solely caught a glimpse of those small fish with their purple cheeks, it might have been well worth the submersion.

Whereas I clumsily labored to maintain from getting flushed downstream, these little fish navigated the present with grace and ease.

As I clawed my method again to the riverbank, I noticed a flash of coloration.  I believed it was one other rosyfaced shiner, however this one was embedded into the underside and was orange moderately than purple.

I noticed that the cobble I used to be digging into wasn’t all rock, however that I used to be in the course of a freshwater mussel mattress.  Their shells have been drab and fuzzy with algae and diatoms in order that they blended in completely with the encompassing rock. 

However their glowing orange and tiger striped mantles that appear to glow by the murk and in opposition to the drab background, gave them away. 

Freshwater mussels are sometimes missed in rivers and streams. However these creatures play a significant ecological position. They usually’re in bother.

Colourful Filters

Freshwater mussels are bivalves like their marine clam and oyster counterparts, however not like the marine blue mussels we’re used to getting served steamed with drawn butter at eating places, these freshwater species are higher for river filtration than for consuming. They’re filter feeders. 

They draw river water in by an incurrent siphon and filter out planktonic algae and diatoms which they ship to their mouths and digestive tract. They spit all of the inedible materials they filter from the water, like sediment, to the underside as pseudo feces.

The brilliant spots that appeared to glow from between the rocks are the incurrent and excurrent siphons.  The query is why are they so colourful? What goal does the colour serve?

Possibly the colours serve no goal. Possibly they’re colourful simply to be colourful.  Why does every thing need to be utilitarian?

Freshwater mussels actually carry out critically vital ecosystem capabilities like filtering 8-15 gallons of water per day per mussel which has led them to be known as the livers of the river.

However I believe their magnificence and significance transcends the what-have-you-done-for-me ecosystem service human-centric worth we place on them.  This was evident as I peered at a backyard of siphons—yellows, oranges, lotions, and indigos, strong coloration and tiger-striped patterned, poking by the fuzzy olive drab of the encompassing cobble.

Mussel Replica is Weirder than You Assume

One rationalization of the colours that makes as a lot sense as another is copy.

Male mussels eject sperm into the water. Females take the sperm in by their incurrent siphon the place it fertilizes eggs. Fertilized eggs, name glochidia, want an middleman host so as to full their growth and switch right into a juvenile mussel.

That host varies with species of mussel. Most use fish, some use crayfish and some even use aquatic bugs.  Some mussel species aren’t very explicit; any form of fish will do.  Others are very discerning and solely a particular form of darter can function the host. 

Regardless, a feminine mussel must infest the host together with her glochidia.  If she have been to only spew them into the water, their possibilities of discovering the correct host aren’t nice. 

So feminine mussels develop methods to lure host fish into their marsupial-like gills, the pouches the place the glochidia are saved. A potential rationalization for the ornate colours is to draw fish as a part of a fancy reproductive technique. 

I noticed some movement on the underside and thought a rosyfaced shiner was again enjoying in my slick.  Besides this fish was stationary because it twitched.

Then I noticed I had been fooled. This was a feminine Lampsilis mussel working her lure.

The Lure of the Mussel

Some species go well past merely having brightly coloured siphons to draw fish.  The females of some mussels really make, and work, lures that seem like the meals of the species of fish they rely on for his or her glochidia to finish their growth.

This feminine Lampsilis was working hers.  It had two distinct eye spots, and a trailing tail which she twitched in order that it regarded like a minnow swimming in a present. If an unsuspecting sunny is available in to take a chunk, her marsupial gills will rupture and the glochidia will latch on to the sunfish’s gills and fins the place they may dwell parasitically for a couple of month as they metamorphose right into a juvenile mussel. 

Needing a bunch to ensure that your infants to finish their growth is dangerous.  If one thing occurs to the host, in order that they aren’t accessible for glochidia to connect and become juvenile mussels, the entire system turns into fragile and there’s a hazard that producing the subsequent technology will fail fully.

In case you are a generalist and might use a number of totally different species as hosts your danger of reproductive failure is decrease than should you rely on one species specifically.  If utilizing a bunch is so dangerous why develop that technique, and if relying on one host is even worse, why do it?

In case you are a non-mobile animal the advantages of utilizing a cellular host makes good sense to redistribute your kin all through the river.  Mussels have ft—that look extra like a giant tongue than our toed anatomy—and might transfer concerning the riverbed for restricted distances. 

Their internet motion nevertheless might be downstream as they get pushed down river with heavy flows.  Attaching your infants to the gills of an upstream swimming fish makes good sense and is in truth an ingenious technique.

Mussels and fish have been on the planet collectively for 200 million years and we are able to guess the relationships between mussels and their fish hosts are as previous. Mussels developed these reproductive methods lengthy earlier than people got here alongside to meddle with them. These complicated reproductive ways have been reliable and efficient, not less than till people arrived on the scene.   

As we dammed rivers and polluted them with fertilizers, sediments and chemical compounds these reproductive relationships which stood the check of evolutionary time all of a sudden didn’t make sense anymore and techniques that have been safe at the moment are fragile.

This is among the causes freshwater mussels are among the most in danger teams of organisms on the planet. There are 1000 species of freshwater mussel on earth. North America is the variety scorching spot with 300 species.  Seventy p.c of North American species are imperiled or extinct.  As a result of they’re so properly camouflaged and seem like backside cobble their losses have gone largely unnoticed.

Due to their cryptic nature they want us to inform their tales and be their advocates. 

Chilly and shivering, I clawed my method again to the riverbank humbled by the ancients I watched at this time.  I used to be grateful for the chance to witness this primeval dance of enticement. The identical present attempting to throw me down river does the identical factor to the mussels. Their capability to make uncanny lures, with out the flexibility to ever see what their lure is mimicking conjures up awe.  

That these mussels are right here attractive a bunch to return alongside, within the face of a number of threats, conjures up hope.