Mola mola: The Flying Pancake of the Sea

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Mola mola, the ocean sunfish
Mola mola, the ocean sunfish. Photo © U.S. National Oceanic and Atmospheric Administration

Look at that guy. He’s ridiculous.
He’s glorious.
Or she, not sure. Didn’t ask, thought it’d be rude.

This, folks, is the Mola mola, also known as the ocean sunfish. It is, I assure you, a fish.

“Why the hell are you showing us a picture of a fish that got run over by a 1998 Honda Civic?” you might be asking. Well, I’m not. First of all, a Civic would have done worse than that. This looks more like the work of a ’79 Pinto. But more importantly, there is NOTHING wrong with that fish. That’s just what they look like. They are just fucking wild AF.

Not to be confused (not that you would) with members of the family Centrarchidae, which are also called sunfish, the ocean sunfish is one of the biggest, weirdest fish you’ll ever find anywhere. In Germany they call it the “schwimmender kopf”, which translates to “swimming head”, which is pretty spot-on, honestly. They seem to be found all around the world, in pretty much every area of temperate and tropical ocean. We usually find them relatively near the coasts, but they are sometimes found out in the middle of nowhere, and since we still don’t know a whole hell of a lot about their range and movements, they may be more common out in the open sea than we realize.

Mola mola with a crowd of people
The same mola photo you’ll see in every article because it’s public domain

Molas are huge. Fucking giants. They are considered the largest bony fish in the world by mass. There are bigger fish, most notably the whale shark, but scientists are jerks and like to make sharks feel bad about themselves, so they take every chance they get to point out that sharks have skeletons made of cartilage rather than bone and therefore they don’t count for some reason. At any rate, molas get to be over 2 meters long, 2.5 meters tall, and weigh up to 1000 kilos, with the largest on record being around 2300 kilograms. (I ain’t gonna convert to feet and pounds, you guys need to learn metric, and the best way to do that is to start converting it on your own every chance you get).

If you really need a comparison, they are WAY bigger than your penis. And just as weird looking. The Mola mola basically has no tail. You can see they have a sort of flap on their butt there, with a little bit of fin, but it’s hardly worth mentioning. Their dorsal fin (top) and anal fin (bottom and stop giggling) have turned in to long thin wings, and they swim more like a sideways penguin than a fish. Their mouths are permanently open and their teeth have fused in to a beak. They also have this really thick layer of skin that’s as tough as tire rubber and abrasive like sandpaper. They are, scientifically speaking, janked as hell.

There’s always room for Jell-o

I’d always heard that molas were obligate gelativores. Okay, now you’re looking at me funny. Do I have food in my beard again? Oh, I see. Well, obligate, as in “obligation”, just means this is something they HAVE to eat. An obligate carnivore has to eat meat, it cannot survive on plants. But the fuck is a gelativore? Is that what happens when you’re in the hospital and the only thing you eat for 5 days is Jell-o and cottage cheese? Well… I mean, sort of. A gelativore is a critter that only eats animals that are basically made of goo. Jellyfish (also referred to as goo-sacs), salps (clone-tubes), and ctenophores (jelly-buddies) are all goo-based lifeforms. There are a few animals, like the leatherback sea turtle, that have to eat them to survive and that consume almost nothing else, and they are gelativores.

Beautiful Mola mola
They’re oddly beautiful Photo © Ilse Reijs and Jan-Noud Hutten

Well… never mind all that, because it turns out molas really aren’t gelativores. We used to think they were, but luckily, science is always progressing. We’ve learned something since the last time I checked in on them. While they do eat jellyfish, a DNA analysis of mola stomach contents reveals that jellyfish only make up about 15% of the adult diet. Otherwise, it turns out they eat a wide range of small fish, invertebrates, plankton, and even a little sea grass. Basically whatever they can get in their mouths despite having the mobility of a trash can lid.

Anyway, back to the parasites. Oh, I never mentioned parasites to begin with? Well, in my mind, that’s all I’ve been talking about, because molas are famous for their parasites. These fish are basically entire ecosystems all by themselves. They have 40+ different species of flatworms (icky bois), copepods (swimmer-jobs) and other critters that live on and in their skin, eyes, gills, livers, and digestive tracts. It’s nothing to find a mola with a dozen copepods burrowed in to their skin, trailing long ribbons of eggs in the water behind them like streamers on the handlebars of your childhood bicycle, except infinitely more disgusting. Look in their guts, and it’s just wads of living spaghetti in there. (Stay tuned for my next article, “Do You Know Where Spaghetti REALLY Comes From?”) You could spend your whole life just studying ocean sunfish parasites, and it would be a life well spent.

Spaghetti. Or intestinal parasites.
Delicious meal, or a wormy nightmare? Photo © Christine Sandu

This dramatic parasite load leads to one of their coolest behaviors. Molas are one of a number of fish species that make use of marine cleaning stations. Look, I get it. Up there I was babbling about Ford Pintos and clone tubes, and now you’re not sure if I’m kidding or not, but I’m not. There really are cleaning stations out in the ocean, specific places where big fish know they can go to have smaller fish or shrimp pick parasites off of them. The cleaner fish in turn know that they probably maybe won’t get eaten while they get a free meal. The behavior of both the cleaners and their clients is a pretty incredible thing just by itself. For instance, they seem to have worked out a system to make sure both sides stay honest and neither one hurts the other. But wait, there’s more!

But wait, there’s Mola?

Some of these parasites on molas are pretty big and dig really deep in to their skin. The smaller fish and shrimp can’t always pull the whole thing off. They just bite half of it off and the rest stays stuck in there. So what to do? Well… ocean sunfish got their common name because they are often seen “sunning” themselves on the surface of the ocean. They float on their sides for a while before going back down to the depths, where they can be found over 600 meters down when they’re on a feeding run. We used to think this basking behavior must be a way to warm up after spending so long down in the deeper, colder water. But the data on this has proven to be inconclusive, and warming up may have nothing to do with it.

What we do know for a fact, though, is that at least sometimes they do this because they are looking for seabirds to dig the bigger parasites out of their skin. They go up to a floating mass of kelp where seagulls like to hang out, or they find an albatross taking a breather and floating on the waves, and they present themselves for inspection. They’ve even been seen following the birds around if they ignore them at first. And sure enough, often the gulls and albatrosses will use their beaks to clean the worst of the freeloaders out of the mola’s skin. It’s like going to the park to feed ducks, except instead of giving them bread, you’re letting them bite your flesh and rip out weird blood-sucking invertebrates. Fun for the whole family!

Mola basking
An ocean sunfish, sunning itself in the ocean

People can be dicks

And now, unfortunately, I have to tell you about the shitty part. See, commercial fishing fleets don’t always do a good job of catching the fish they’re actually looking to sell. Though there are methods and specialized gear to help with this problem, not everyone bothers. Even the boats that make the effort still catch plenty of things by accident. When a boat catches a species it doesn’t intend to sell, that’s called bycatch. And it turns out, ocean sunfish are commonly caught as bycatch. They get caught in nets or they take the bait on longline hooks. Molas are eaten in Japan, Taiwan, and a few other places, but their local fisheries provide enough for those markets. When sunfish are caught elsewhere, it’s not profitable to keep them and transport them, so they just get tossed back.

Sometimes they survive the process and are returned alive, but not always. Even when they do, they suffer injuries that they may not recover from. Lots of species have trouble with bycatch, but sunfish really get the shaft sometimes. There was a commercial fleet off the coast of Spain for a while that was fishing for swordfish, and they wound up catching almost nothing but molas and not many swordfish. Sometimes over 90% of their catch was unwanted sunfish. They eventually put a stop to that, but fleets targeting swordfish still commonly have 25% of their catch be molas that are tossed back, dead or alive. On top of that, sailors on some boats will just kill any sunfish they catch, because they consider them to be a nuisance.

I love humans. I really, really do.

Now, molas had a pretty healthy global population to begin with, so they’re doing pretty okay overall. But their numbers have still been reduced by about 30%, which isn’t great. They can handle it for now, but we need to make sure it doesn’t get much worse.

The amount of diapers alone would be insane

Which leads us back to the fun stuff. Sex. Part of the reason that Mola mola hasn’t been just wiped out by all this fishing bycatch, is that it turns out to be one of the most prolific breeders around. Lady sunfish only have one ovary, but that single ovary can crank out up to 300 million eggs at a go. 300,000,000. That’s ba-nay-nay. In order to understand how many eggs that is, you’d have to just get drunk and give up, because you’re never going to understand it, it’s too crazy big. Part of the reason they can produce so many eggs is that these eggs are tiny. They’re only a millimeter wide, so they can cram more eggs into the ovary than if they had bigger eggs. Strangely enough, what hatches out of a mola egg isn’t a mola, but some sort of weird spiky ball with eyeballs.

Larval Mola
Larval Mola sp. Photo © G. David Johnson

Look at that guy… no way that grows up to be a giant swimming parasite plate. But it does, actually, and when you remember how big the adults can be, the amount they have to grow is incredible. Your growth spurts in the 8th grade were weaksauce compared to this. Between hatching and adulthood, molas increase in size by fucking motherfucking 60 million times their birth size. For a human to grow that much, you’d have to be… umm… holy damn. 2 x 108 kilograms. I don’t even know how to visualize how absurdly huge that would make you as an adult. I’m literally at a loss and am not even going to try. Let’s just say, nobody would dare face you in the sumo ring.

So that’s the Mola mola, the ocean sunfish, one of the wildest critters you’re going to find anywhere. I love fish that challenge your ideas of what fish look like, of what a fish even is, and these guys definitely are near the top of that list. No tail, filled with hitchhikers, an insane difference between the babies and the adults, and on top of all that they pester seagulls in to cleaning them. Anybody that can get a gull to do them a favor is ahead of the game if you ask me.

And now, if you’ll excuse me, I need to go buy a pallet of ice cream. I’ve got a lot of work to do if I’m going to reach 60 million times my birth weight in time to be a mola for Halloween.

MORE READING:
Oceansunfish.org
Why does the ocean sunfish bask?
The biology and ecology of the ocean sunfish Mola mola

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