[ intro ] Whether you’re a farmer with acres of veggies or an urbanite tending to your windowsill herb garden, we humans have been growing and cultivating food for thousands of years.

And while picturesque rolling acres might come to mind when we think of farming, we also farm the sea, harvesting a wide range of food for ourselves, from seaweed to oysters. But humans aren’t the only salt-water farmers.

Many other species tend to their underwater gardens and grow food for themselves, growing crops like fungi and bacteria! So here are five species that specialize in growing their own crops under the sea. Ants may be fungi’s number one fan, with many farming fungi as their main food source.

But some snail species take their love for fungi to a whole new level; they farm them in saltwater. Littoraria irrorata, also known as the marsh snail, is usually found in salt marshes along North America’s Atlantic coast. For a long time, it was thought that this snail preferred to eat dead and decomposing debris, but around 2001, scientists found it eating something different...a living plant.

And this wasn’t your casual eating; it turns out the snail was actually inflicting wounds upon and keeping old ones open in cordgrass. But they weren’t actually feeding on the plant . They were creating the perfect home for colonies of fungi, the snail’s food of choice!

Researchers found not one but multiple species of ascomycetes fungi inside the plant's wounds. In fact, there were more of these fungi on the leaves that the snails managed than on uninjured leaf surfaces. And these snails go beyond just slicing up leaves to encourage the growth of their favorite food.

They also have a secret weapon that’s pretty common among farmers, they use manure to boost their crops. For the marsh snail, that means concentrating its own poop on the damaged leaves. Scientists compared how much poop there was on different plant surfaces and found that injured plants had about four times more poop than other uninjured parts of the plant.

And that makes a huge difference when it comes to fungal growth, increasing its biomass by over 170%. But, as you might guess, this farming practice isn’t so great for the plants involved, decreasing the cordgrass’s growth between 40 and 100% So, although these snails are looking to have their food locally sourced, their choices are probably better for them than for the cordgrass. And snails aren’t the only species manipulating cordgrass for a meal.

Meet the ragworm, a type of marine polychaete, which is more interested in growing the cordgrass itself rather than damaging it. For centuries, humans have grown baby plants, known as sprouts, to eat as a supplement to their diet. But we weren’t the only ones doing this; ragworms have also mastered the art of homegrown sprouts, and for a very good reason.

Cordgrass seeds themselves aren’t actually edible to these worms; their tough husk exterior appears to prevent them from being able to get through to the nutritious innards. But these worms work around this by essentially planting them, and waiting until they become a more palatable treat! they do this by burying cordgrass seeds in their burrows, which ensures they don’t get carried away by any water movement. And alright, maybe these worms aren’t exactly the hardest working farmers.

It’s not like they carefully tend to their seed stash. But taking this simple step to bury the seeds makes a huge difference to the diet of these worms. because sprouted seeds are highly nutritious and more easily digested. And one 2016 study published in the journal Ecology found that ragworms feeding on sprouted seeds put on significantly more weight than those without access to seeds.

So, in the case of these ragworms, all that’s needed is some planting and a bit of patience to turn something inedible into a nutrient-rich meal. If you’ve ever grown your own food, you probably learned the importance of keeping weeds in check and pests at bay. And cone-shaped marine snails, also known as limpets, abide by that tenet.

You can spot them on rocks during a low tide keeping a tidy garden while making sure their crop isn’t taken over or eaten by others. Once they’ve grown big enough to have their own territories, owl limpets carefully manage their own intertidal space, which is where land meets the ocean during tides. Each limpet has its own cleanly kept section of rock that’s covered in an algal film they can graze away at and upkeep to maintain a steady supply of algae for themselves.

But they have to keep a vigilant eye on their crops because other critters, like predatory snails or other limpets, are waiting to seize the opportunity and gobble up all the algal film. Even squatters like anemones and barnacles might try to stubbornly attach themselves within an owl limpet’s patch of rock. And while limpets may not look like the greatest defenders, I mean, it’s not like they fence their garden, they have to defend their territory themselves by acting like both the sheep and the sheepdog in one.

If you’re wondering how this sluggish cone-shaped creature could possibly go on the defense, they take a pretty direct approach, with some determined shoving The owl limpet jams its shell under the intruder, either pushing until the unwanted guest leaves the territory or is entirely dislodged. All in a day's work to keep your algae crop thick and luscious. And limpets aren’t the only ones that rely on algae!

It’s actually a pretty widespread crop, so a lot of animals depend on it as food. Turns out though, not all algae are created equal in terms of how tasty they are. A damselfish, appropriately named the dusky farmerfish, is an algae eater but only cares for one in particular, the red algae.~ These farmer fish carefully weed out all the undesirable algae varieties from their crop to ensure only the good stuff is thriving.

If another critter dares to come near their little garden, they will fight aggressively to defend their territory, much like the owl limpets. And despite being munched on by the farmer, this type of algae benefits from the relationship. Because without the help of these damselfish defenders, the red algae it protects might otherwise be outmatched by other more aggressive species.

Which might be why researchers studying this peculiar relationship haven’t been able to find it anywhere outside of damselfish turf! it appears that the grazing it endures under the watchful eye of its fishy farmer is a fair trade for an otherwise safe space to grow. So far, the world’s crop farmers tend to be pretty focused on plants, fungi, or algae. But way down in the depths of the sea, there’s a species of crab that farms a food source you might not expect... bacteria.

They're called Yeti crabs because, they have a look. It’s no wonder these crabs were only discovered in 2005. After all, they are only found around one thousand meters deep.

These crabs hang out around methane vents on the ocean floor that spew out gases like hydrogen sulfide and methane. And the scientists who first observed these fuzzy-looking crabs didn’t actually see them scavenging food from the surfaces around them. Instead, they saw the crabs doing a strange slow-motion dance at the openings of these vents!

Waving their claws slowly back and forth was more than a peculiar dance; it also increased the bacterial growth on their claws. Encouraging bacteria to grow on your own bodies might seem a bit unorthodox, but in addition to doing the wave, the scientists also witnessed the yeti crabs picking away at their own bodies, revealing that the bacteria they were growing was, in fact, their dinner. It appears that these deep-sea crustaceans prefer to munch on bacterial colonies found growing on their own bodies, especially on their setae, which are the hair-like bristles that completely cover their claws.

They even have a specialized seta that looks just like a microscopic comb , their very own built-in harvesting tool. The crab uses it to scrape the bacteria off their body and into their mouth! But these bacteria are kind of finicky to grow; they need specific chemicals that spew out of the vent but also oxygen in order to thrive.

So the crab waves their claws around in the water column to increase the exposure to these precious resources while encouraging further bacterial growth on their bodies and therefore growing an even larger crop. ~ And they aren’t the only ones with home-grown crops on their bodies, there’s another species of crab and a shrimp that have a similar strategy. Because who needs a plot of land when you can graze straight from your body! So next time you add spirulina to your morning smoothie or seaweed to your soup, think of the hardworking marine critters diligently maintaining their underwater crops and ensuring a healthy harvest for the days to come.

And maybe just be thankful you’re not left to munch bacteria off your own arm? But hey, to each their own! Thanks for watching this episode of SciShow!

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