A mouthful of mussel marsupia, and nowhere to run
You'll be grateful you weren't born a fish after reading this!
For us homo sapiens, reproduction is a relatively straight-forward process. Obviously, the process of gestating and giving birth isn’t simple, but the conception portion of events is pretty basic, and at the very least, human reproduction only requires the involvement of one type of organism: humans. If we had to reproduce the way freshwater families of bivalve molluscs do, we’d need to climb the taxonomic chart to involve an organism about 10 steps removed from us to be able to reproduce. There would be a lot fewer new Jesikah’s, Charleigh’s, and Wayne’s being born if this were the case!
The lampsilis is a freshwater mussel that has mastered the art of tricking fish into biting them so they can shoot their jizz into the fish’s mouth. If you’re thinking “Wow, way to come out of the gate swinging,” well. Imagine how the fish feels when it gets a mouthful of surprise mussel jizz! (Was this was an intentional strategy to get you into the mindset of the unsuspecting bass who’s just gotten a nasty shock, or was it the case that I couldn’t figure out a less bombastic way to start out telling a story this exciting? I leave it to you to decide.) Technically, it’s not jizz, it’s fertilized mussel eggs/tiny larvae getting shot into the fish’s mouth, but the fish doesn’t know that, plus “mussel jizz” is funny. To me.
To understand why a lampsilis mussel would want to jizz into a trout’s mouth, we first must have a basic understanding of freshwater mussel reproduction. Typically, a female mussel has the eggs brooding in her gills in a little special chamber called a marsupia. She waits to catch some errant sperm from the water through her siphons, which is a slightly inefficient method to reproduce if you ask me but then again, a lady mussel never has to worry about creepy dudes trying to penetrate her, so maybe mussels are smarter than us. Male mussels do their part by shooting sperm out into the water willy nilly, hoping it gets sucked into a lady somewhere along the riverbed, in a reproductive methodology known as “jerk off and hope for the best.” 1 Now, once the female mussel has collected the free-floating sperm and fertilized her brooding eggs, they grow from egg to larva (called glochidia), and the fun really starts.
The tiny mussel larvae are microscopic and raring for blood. Literally. Because they need fish blood in order to grow/survive/turn into an adult mussel. MUSSEL LARVAE ARE VAMPIRES, YOU HEARD IT HERE FIRST! 2 Many species of mussel mommas simply release the larvae into the water with a prayer that their glochidia land inside a fish somewhere along the line. The lampsilis mother, however, has developed a strategy for a more sure-fire success rate in terms of finding her babies a fishy host from whom to suck nutrients out of.
For this next part we’ll need to know a little bit about mussel physiology, for which purposes I have included the diagram below:
See the part labeled “mantle flap?” In the lampsilis community, the mantle flaps grow to be displayed outside of the shell, into little fleshy appendages specifically designed to entice and trap foolish fishes into biting them by imitating the appearance and movements of the minnow (a tiny fish that bigger fish like to munch on as a snack, if you’re unfamiliar). The crafty lampy mommies have derived a system that is genius: when a fish strikes, it physically triggers the mussel’s marsupia (special gill-located nursery chambers, if you recall from three paragraphs ago) to release a cloud of glochidia bb’s, which then get sucked straight into that fish’s mouth, because predatory freshwater fish have mouths that work on vacuum suctioning power. When they open, shit comes flooding in, and sometimes, that shit includes a cloud of mussel offspring, and by the time it happens there’s not much the poor fish can do about the mouthful of larvae they’ve just received. They’ve been suckered and are about to be suckered even more, and they didn’t even get a tasty treat out of it! (Well, maybe glochidia spawn clouds are tasty, I don’t know, personally, and while I’m very interested in the answer to this question I’m not committed enough to go find out.)
Check out this fleshy fishing lure! They even wriggle realistically from time to time, imitating the frenetic movements of a minnow spending life constantly swimming around stressed about being the bottom of the food chain.
The most successful lampsilis mothers are the ones who can grow the most true-to-life lures out of their mantles. This has led to evolutionary paths creating mussels who are so fucking good at imitating fish, you almost don’t believe it when you see it. But here’s the thing: mussels don’t have eyes. How do the female lampsilis know what the fuck a minnow looks like in order to try and imitate in the first place? How do they know?!? THEY DON’T HAVE EYES! They couldn’t see a minnow if you slapped them with it! HOW. THE FUCK. DO THEY KNOW!?! 3
Once the glochidia are out of the mother’s mantle, her parental duties come to an end. She has located them a fish to infiltrate, and that’s all she can offer. The task of developing a parasitic relationship with a perch is the microscopic larva’s problem now. A lot of responsibility for something so fucking tiny!
The ideal situation for a newly released mussel larva is to land inside the gills of the fish, where they will glom on tight and wait for the encystment to begin. This is the part that really gets me: the glochidia don’t just hold on to the gills and begin sucking blood out of them. They BECOME PART OF THE fuCKING FISH when the fish starts to grow cells over them, ensconcing them entirely within FISH TISSUE! They hang out as part of the fish’s body for a period of several days to a few weeks, depending on the water temperature and the type of fish (some fish have strong enough immune responses that the larva will be killed, so, you’re shit out of luck if you get sucked into the mouth of an incompatible species), absorbing nutrients from the fish’s bloodstream. Eventually, the glochidia drop off of the gills and out of the fish, somehow; nobody has figured out how they escape the encystment. Mussel babies are the David Blaine of the mollusc world!
Once they’ve said farewell to their former fish hosts, the mussel children go about the business of growing up, where ever they’ve landed. They serve an important ecological function in this world, because they filter the water around them naturally as they feed. Really, the fish who are being preyed on here are basically just doing their part to help out their ecosystem maintenance team! It’s all gravy in the end. 4
Nature Is Healing:
This is a section where I provide some of my favorite animals news headlines of the week.
An inspirational QUEEN: A Cave-Dwelling Salamander Didn’t Move for Seven Years
Hell yeah! acab! Fly free comrade! Pink Floyd, a flamingo on the lam from a Kansas zoo since 2005, is seen again in Texas
Lazy Geoff is an icon: a Twitter thread of wildlife biologists talking about the laziest animals they’ve ever tracked
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Sources:
Absurd Creature of the Week: This Mussel Does an Incredible Impression of a Fish | WIRED
Fresh Water Mussel Collection: Introduction - Anatomy
How do mussels reproduce?
Bass Eyesight, Motion Detection, and Visual Lures
Lampsilis cariosa
Mussel Glossary
“Jerk off and hope for the best” is not what mussel scientists call it, to be clear; I made that phrase up. But it’s what they should call it.
It would probably be more accurate to say mussel larvae are vampiric, rather than being themselves vampires, but I’m writing this and I’m having fun and that’s what counts!
The answer to “how the fuck do they know” is basically: evolution, natural selection, etc etc etc. But I’ve known about this whole situation for weeks now and every time I think about it I’m still just like, BUT HOW DO THEY KNOW?!? I cannot stress this enough, they don’t have fucking EYES!
Unless you’re an early juvenile fish, in which case, some gills full of glochidia could actually kill you. I didn’t want to end on a downer and nothing’s sadder than teenage fish failing to reach their potential!