Symbiotic Relationships: Partnerships in Nature

Symbiotic animal relationships on land and sea

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Within the ecosystems of the world, there are plants and animals that form mutually beneficial relationships. There are also those that form relationships that benefit one species more than the other. In both cases, this is known as symbiosis.

You might be surprised at just how many symbiotic relationships there are within nature.

What is Symbiosis?

What is symbiosis?

The word symbiosis comes from the Greek meaning living together, and that’s the perfect description of what it is. You see, symbiosis is a term that refers to a relationship between two different species, which are called symbionts. 

The relationship between the two may be mutual, commensalistic, or even parasitic and one or both species may rely on the other for survival. That said, there are other forms of symbiosis that are not obligatory and each of the species could live without the other if necessary.

Types of Symbiotic Relationships

Types of symbiotic relationships

Depending on the species and the relationship, there can be different types of symbiosis. These are mutualism, commensalism, and parasitism. Let’s take a closer look at how each of these relationships works.

1. Mutualism

Mutualism refers to symbiotic relationships where both species or organisms benefit from the association. For example, one organism may provide the other with food.

However, mutualism can benefit organisms in a variety of ways, such as by providing shelter, protection, and many other things.

These mutual relationships may be obligate, whereby the organisms need the relationship to survive, or facultative, where the species could survive without one another.

Examples of Mutualism Relationships

  • The plover bird cleans the teeth of alligators benefitting from a meal while the alligator benefits from this avian dentistry.
  • Hummingbirds and flowers have a mutually beneficial relationship whereby the bird obtains food in the form of nectar while the flower benefits from cross-pollination for reproduction. This is also the case with bees and flowers who collect pollen and nectar.
  • The clownfish is able to live among sea anemones thanks to a special secretion where other fish would be stung. This offers them protection while the sea anemone benefits because the clownfish draws in prey.

2. Commensalism

Commensalism refers to symbiotic relationships where only one organism benefits in some way, whether that be for food, shelter, or anything else. However, unlike a parasitic relationship, host animals and plants involved in commensalism are not harmed or affected in any way.

Examples of Commensalism Relationships

  • Spiders use trees and plants to build webs, and while the trees and plants receive no harm from this, they don’t benefit either.
  • Some types of weeds, like burdock, have sticky seeds that attach to animals. These will then fall off the animal, allowing for the reproduction of the weed at no cost to the animal.
  • Pseudoscorpions are unable to move from place to place on their own, so they attach to a larger insect and hitch a ride.
  • Remora fish attach to sharks to eat any leftovers from the shark’s meal, saving them from hunting. This doesn’t affect the shark as the fish doesn’t take any of its food, only what is left over.

3. Parasitism

We hear about parasites in the animal kingdom all the time and this is another form of symbiotic relationship. However, in this case, only one of the organisms will benefit and the other one is harmed or even killed in the process. The one that does not benefit is called the host.

Examples of Parasitic Relationships

  • Some types of barnacles will attach to whales which can cause the whale problems with swimming.
  • Ticks attach to a variety of warm-blooded animals, including humans, to use the blood as food. However, the host loses precious blood, and the tick may also cause pain or irritation.
  • Head lice are common among humans and live on the scalp to get food. However, for the host, this results in irritation and skin itching.
  • The parasitoid wasp will lay its eggs on another insect. Once the eggs hatch, the young feed on the body of the host, killing it.
  • Cuckoos will lay their eggs in the nest of another bird, transferring their parenting responsibilities. However, when the bird puts its own egg in, it will remove one of the host’s eggs, therefore ending that hatchling’s chance of survival.

Symbiotic Relationships between Animals on Land

There are lots of land animals that need the help of other terrestrial creatures to survive, and here we find many interesting symbiotic relationships.

1. Black Ants & Aphids

One of the most well-known symbiotic relationships within the insect kingdom is that of the black ant and the aphid. The association between these two creatures is mutually beneficial and it’s all thanks to a substance known as honeydew.

No, I’m not talking about the melon. Honeydew is something that is produced by aphids and is a sugar food that ants go crazy for. Studies have even shown that the dopamine contained within honeydew can affect the aggression in ants who will then use this to encourage the reproduction of more high-quality honeydew producing aphids.

But it’s not all in vain for the aphids who are offered protection from predators by their ant comrades.

2. Warthog & Mongoose

Imagine having a mongoose hair stylist! That makes it sound a little more glam than it is, but this mutualistic relationship between warthogs and mongoose is certainly unique.

It’s been shown that warthogs will actively seek out the services of mongooses who will remove annoying ticks from their bodies. This is naturally a huge relief for the warthog while the mongoose gets a tasty meal for nothing more than a bit of nit-picking!

3. Burrowing Tarantula & Dotted Humming Frog

What do frogs and giant hairy spiders have in common? Not much, it would seem at first glance but consider the burrowing tarantula and the dotted humming frog. They have a mutualistic relationship that benefits both species who should be predator and prey.

It’s thought that the dotted humming frog secretes a chemical that tells the tarantula not to eat it. This allows the frog to take shelter in the spider’s burrow during the day, with the eight-legged creature standing guard to protect from predators. In return, these little frogs will feast on ants that may otherwise pose a threat to the tarantula’s eggs.

4. Coyote & Badgers

Badgers and coyotes often hunt for the same prey, so you would think that this would put them in direct competition with one another. While there are conflicts between the species, they’re also known to hunt together in a very unique and interesting mutual relationship.

When hunting for things like prairie dogs, the two have often been seen together. The coyotes have speed to chase prey above ground but should it try to escape below the surface, the badger comes along to burrow down and follow it. It’s been demonstrated to be an effective hunting technique as prey seems to be much more vulnerable when both species are in pursuit.

5. Cape Buffalo & Oxpecker

One of Africa’s Big Five the Cape buffalo is a magnificent species, if not incredibly dangerous. Yet while this is a huge beast, the animal has a symbiotic relationship with a small bird known as the oxpecker, of which there are two species; the red billed and yellow billed oxpeckers.

Regardless of the species, these little birds enjoy the opportunity to take shelter and hitch a ride on the buffalo. Many would argue that this is an example of parasitism because the oxpecker has far more benefits, including a free meal from the ticks it removes. However, since the buffalo is benefitting from the removal of said ticks, I’m inclined to agree with those that say this is a mutually beneficial relationship, even if the oxpecker does take a little more from it.

6. Ostrich & Zebra

The zebra and the ostrich are among some of the most common prey animals in Africa. While they could survive without one another, their mutually beneficial relationship does ensure a higher survival rate for each species when it comes to predators like lions and hyenas.

It all comes down to how each animal detects an incoming predator. For example, the ostrich has very good eyesight and, with its height, is able to see much further than the relatively short zebra. On the other hand, zebras have impeccable hearing so may pick up on sounds much more quickly.

Combining these powers allows each animal to avoid becoming a meal much more effectively than if they were working alone. What’s more, both species travel in large numbers, and where there’s numbers, there is better defense, especially when you consider that the zebra and the ostrich boasts a powerful kick.

7. Nile Crocodile & Plover

The plover has no problem getting inside the mouth of a creature that many others would run in fear from. But the Nile croc allows this little bird to dig around in its teeth and remove any scraps that got stuck from its last meal.

But this isn’t a one-way relationship; it’s very mutual. While the crocodile has clean, fresh gnashers, the plover gets a meal that it doesn’t even have to hunt for.

8. Brown-Headed Cowbird & Nesting Songbirds

Can cowbird nestlings harm the hosts nestlings?
Kelly Colgan Azar / Flickr / CC BY-ND 2.0

The brown-headed cowbird is considered an invasive species in many parts of the US because they’re not a native species. Plus, they’re nothing but a parasitic pest to many of the country’s native songbirds.

Brown-headed cowbirds are brood parasites that will lay their eggs in the nests of unsuspecting birds like song sparrows, yellow warblers, and eastern towhees. Although, they are known to invade the nests of up to 220 species.

This relationship is only beneficial to the cowbird who has its young raised for it. However, the host suffers since the young cowbird will hatch sooner and grow faster, eating up resources. What’s more, it’s not uncommon for the hatchlings to throw out its sibling eggs.

9. Cattle Egret & Elephant

The cattle egret is well known as a helpful bird in Africa because of its interactions with many species. In fact, it’s thought to make up 51% of all symbiotic birds on the giant continent.

When it comes to elephants, the cattle egret is super helpful since it will remove and eat ticks or parasites found on the body of the large mammal. What’s more, the bird will make a loud sound when it detects predators, giving the elephant time to escape.

Of course, the relationship is mutually beneficial since the cattle egret gets free food and can hitch a ride.

10. Wolves & Ravens

If there’s one thing that wolves and ravens have in common it’s that they both regularly feature in horror stories. But that’s not where their associations end.

Ravens and wolves share an interesting relationship whereby the wolf will make a kill and the raven will hone in and scavenge some of the feast. Amazingly, it’s been observed that it’s actually the raven that takes most of the meat, and in some cases, up to 135 birds have been seen swooping in on what a wolf has just caught.

All of this makes it sound as though the wolf has nothing to gain. But that couldn’t be further from the truth. Ravens act as something of a guard and lookout for the wolves. While both species feed, the ravens remain on high alert. There have even been incidents where ravens circling overhead will act as a distraction to potential prey, allowing the wolf to make its move.

11. Galapagos Lava Lizard & Marine Iguanas

The marine iguana is the only reptile whose main food source comes from the water and it primarily feeds on algae. For this reason, it can be found basking on the coastline, sneezing out excess salt water.

While here, the marine iguana is susceptible to flies and other irritating parasites. However, a much smaller lizard; the Galapagos lava lizard swoops in and eats the flies. This is a mutually beneficial relationship whereby the lava lizard gets a free meal, and the marine iguana is free from pests. The Sally lightfoot crab plays a similar role for the marine iguana.

Symbiotic Relationships in the Ocean

It isn’t only on land that plants and animals are working together. There’s plenty of undersea action happening at the same time.

1. Goby Fish & Pistol Shrimp

There are around 2000 species of goby fish and some, but not all of them, will form a mutualistic relationship with the pistol shrimp. The most common is between the Randall’s Prawn Goby and the pistol shrimp. Their relationship is so close that the pair can often be seen physically attached to one another with the shrimp constantly touching the fish with its antenna.

But why?

Well, the goby benefits from this pairing because pistol shrimps will dig burrows in the substrate that the fish can hide out in. But there’s still space for the shrimp, and the goby has a chemical signal that it uses to communicate with its partner when there’s a predator nearby.

What’s more, it’s also thought that the shrimp will eat the fish’s poop and any parasites on its body, therefore benefitting from a free meal.

2. Pearlfish & Sea Cucumber

Oddly, as many as 14 pearlfish can be found in a sea cucumber’s bum. I bet that’s a sentence you never thought you’d read! But it’s astonishingly true and this is a commensalistic relationship that certainly benefits the pearlfish over the sea cucumber.

You see, no harm comes to the sea cucumber when the pearlfish waits for it to breathe in through its backside and happily swims in to take shelter. But for the pearlfish, this is a safe and comfortable place to rest.

That said, it really depends on the species as there are some that can act as parasites and will feed off the gonads of the helpless sea cucumber.

3. Whales & Barnacles

If there was ever a commensalistic relationship that was so well known, it’s that between a whale and a barnacle. There was even an episode of Spongebob Squarepants where Pearl the whale ended up covered in barnacles. Thankfully, no harm was done, and that’s largely the case in the wild too.

By attaching to the whale, the barnacle is better able to filter feed. But this doesn’t do any damage to the whale. That said, there has been some suggestion that large numbers of barnacles on a whale could affect its ability to swim, making the relationship more parasitic than commensalistic. But this is rare.

4. Sea Anemone & Clownfish

You may be familiar with this pairing from the super cute movie Finding Nemo where Marlin and his son, Nemo, live inside a sea anemone. But this isn’t only the stuff of Disney creators; these fish really do take shelter in anemones which allows them to hide from predators who cannot go inside the anemone because they’ll be stung.

Clownfish have a layer of mucus that makes them immune to the anemone’s sting. But this is a mutual relationship, and the fish draw in other species that the anemone can devour.

5. Sharks & Remora Fish

Another commensalistic relationship that we often see in the ocean occurs between the remora fish and sharks. The remora will attach itself to the body of the shark, feeding on scraps from whatever the shark catches for dinner.

In tropical waters, these fish will use a suction cup on their heads to attach to their chosen shark, and the two live quite happily side by side. The shark suffers no ill effects, and since the remora fish is so small, it’s hardly a heavy load to carry.

While the remora also eats parasites on the shark’s body, this isn’t imperative to the shark’s survival. What’s more, the remora has its very own bodyguard in the shape of one of the world’s most feared fish.

6. Grouper Fish & Moray Eel

The moray eel and the grouper fish have a mutualistic symbiotic relationship that benefits both parties when it comes to hunting. Since eels hunt around coral reefs and groupers are much larger, hunting in the open water, they can work as a team to cover more ground and therefore catch more prey.

And this doesn’t all happen by chance, studies have shown that groupers actually have the ability to send signals to eels when they want to recruit them in a hunting session.

7. Sunburst Anemone & Algae

There is a specific type of algae called zooxanthellae that lives in among the sunburst anemone’s tentacles that, when under the correct light conditions, actually produce food for the anemone. When it does this, it enhances the color of the anemone, making it greener. You’ll notice that sunbursts living in low light conditions are almost devoid of color.

So, does this relationship benefit the algae at all? It certainly does. When the anemone expels carbon dioxide, the algae takes nourishment from this.

8. Spanish Dancer & Emperor Shrimp

The Spanish dancer is a type of nudibranch that primarily feeds on sponges. Inside the gills of the animal, one can find a small creature called the emperor shrimp. One of the main benefits to the shrimp is that it gains shelter and protection, but it’ll also get some food from the Spanish dancer. 

However, this is a mutualistic relationship, and the Spanish Dancer receives a thorough gill cleaning from the shrimp. But let’s not forget that while both organisms benefit, the Spanish dancer also acts as a cab for the inch-long shrimp, who’s more than happy to catch a ride.

9. Decorator Crab & Sea Sponge

You could say that this was a mutually beneficial relationship as the sponge will be presented with a lot of feeding opportunities thanks to the presence of the decorator crab.

However, it’s definitely the crab that benefits more from this pairing as it clips off pieces of the sponge to decorate itself which provides it with camouflage. This comes at no cost to the sponge who may also provide various nutrients for the crab, depending on its species.

Symbiotic Relationships between Animals & Plants

It isn’t only animals that form relationships with one another. Some plant and animal species will work together to form a union, good or bad!

1. Bullhorn Acacia & Acacia Ants

Judy Gallagher / Flickr / CC BY 2.0

Acacia trees are the ideal spot for ants to live since they provide them with shelter in the hollow thorns as well as all the food they could ever wish for. But this isn’t just a relationship that benefits the ants; the acacia tree has its very own colony of bodyguards that prevents herbivores from trying to eat it.

Out of the nine species found on acacia trees, it’s thought that four of these are obligate, meaning they would not be able to survive without the tree. That’s largely to do with the bitter alkaloids found in the tree of which these ants are deficient.

2. Fig Tree & Wasps

Figs are not actually a fruit, they’re what’s known as an inflorescence which is essentially a cluster of seeds within a bulb. But since these seeds are contained within the bulb, they need to be pollinated in a special way; and that’s where wasps come in – literally!

A female wasp will enter the bulb via a small opening at the top called the ostiole. However, this opening is so tight that she loses her wings as she squeezes through. But it may not all be in vain because, if the fig is female, the wasp will pollinate it as well as laying her own eggs.

Sadly, this means the end for the female, but her larvae will hatch and escape the fig to go on and produce further generations. Meanwhile, the fig has been successfully pollinated.

3. Cordyceps Fungus & Bullet Ant

You might hear people calling the bullet ant the zombie ant because of the way it behaves once the parasitic cordyceps fungus takes over. It seems that, once the fungus attaches to the ant, the ant becomes its puppet.

The fungus spews out spores that stick to the ant and spread long tendrils known as mycelia that literally take over the ant’s brain. This compels the ant to find a suitable location on the forest floor that’s perfect for fungal growth and clamp down with its jaws. The fungus is then able to thrive while the poor ant breathes its last breath.

4. Pitcher Plant & Bats

One of the most interesting mutualistic relationships between plants and animals is that of the pitcher plant and the bat; commonly, the wooly bat. But plants like the nepenthes hemsleyana are carnivorous so you’d think that animals would avoid them.

That’s not true; in fact, these plants are known to prey on the bat’s echolocation senses to draw them in. But the plant won’t eat the bat; just its poop!

Wooly bats will nest inside the pitcher plant’s cup, where it is safe and sheltered. While it’s living here, it’ll naturally excrete its waste which is rich in all the right nutrients that the plant needs.

5. Azteca Ants & Cecropia

In Central America, we find the cecropia tree, and where these trees grow, you’re bound to find azteca ants who have a mutually beneficial symbiotic relationship with the trees.

The ants take a carb-packed food source called glycogen from the trees and also find plenty of places to nest. In fact, these ants are obligated to nest in these trees, but they aren’t the only ones benefited from this pairing. 

In fact, the cecropia tree gets repaired by the ants as they scurry around like little workmen. Experiments done by high schoolers have shown that the Azteca ants may be able to repair holes in the tree in as little as 24 hours.

6. Cadaghi Tree & Bees

Aussie beekeepers are actually finding the seeds of the cadagi, a type of eucalypt tree, in and around their beehives. But why is this?

Well, this is all part of a mutualistic symbiotic relationship between the two species. The seeds of the cadagi tree contain a special type of resin that’s perfect for bees when it comes to building their nests.

How does this benefit the tree? Once the bees have taken the resin they need, they proceed to get rid of what’s left of the seed. As long as they deposit it in a location where it can grow, the cadagi can reproduce.

7. Acraea Horta Butterfly & Wild Peach Tree

In South Africa, there’s a very common symbiotic relationship between the wild peach tree and the acraea horta butterfly.

The butterflies use this tree as a place to lay their eggs, which is obviously beneficial to the species. However, when the larvae hatch, they will eat all of the leaves on the wild peach tree, making it almost bare.

Surely this can’t be mutualistic, can it? Actually it is. That’s because the larvae deposit droppings around the tree that act as a fertilizer. What’s more, the tree has the ability to grow a second flush of leaves so there’s no harm done.

8. Clark’s Nutcracker & Whitebark Pine

Both the Clark’s nutcracker and the whitebark pine are keystone species, meaning that the local ecosystem would change immensely if either didn’t exist. They also depend on one another in their mutualistic relationship.

The nutcracker uses the tree for food. It’ll gather seeds and cache many thousands to eat at a later date. That doesn’t initially sound too promising for the tree, but in reality it is because the birds often forget about the cached seeds, which gives them a chance to germinate, ensuring the spread and survival of the whitebark pine.

Bacteria & Human Mutualism Relationship

Bacteria and human mutualism relationship

When you hear the word bacteria, you might recoil in horror, and it’s true that there are lots of types of bad bacteria that you’ll want to stay away from. However, there are also good bacteria that have a mutually beneficial relationship with humans, and we’d unlikely be able to survive without them.

These bacteria can be found in and on each and every one of us; yes, that includes you. They live on your skin and in your gut. In fact, there are so many bacteria in our guts, even more than the number of cells in our bodies, that they can make up to between one and two kilos of your body weight!

Knowing that you’re carrying around the equivalent of a couple of bags of sugar, you’ll likely want to know why these bacteria are so important. It’s all to do with keeping us healthy as these bacteria fight off pathogens and also help to develop our immune systems.

If that wasn’t enough, these microbiota are able to produce vitamins that benefit us as well as aiding in waste processing.

These microscopic organisms also aid our ability to digest certain foods such as fiber. There’s even some suggestion that the type of bacteria we have in our guts can influence our eating habits. And since there are more than 1000 species of microbiota, that’s hardly surprising.

So how do the bacteria benefit from this pairing? It’s simple, the human body provides them with a place they can thrive. The conditions in the gut are just right for these little organisms and without us, they’d surely die.

There are also tiny bacteria living on our skin and in our nose and throat. These organisms also need a place to live, and we provide that for them. In return, they’ll block the way for harmful microbes which they eat, preventing us from getting sick.

Yes, there are bad bacteria that sometimes get through and that usually happens when there is a disruption to the microbiome. However, it can also be as a result of drugs like antibiotics which are designed to kill bacteria, and they don’t differentiate between good and bad. But for the most part, those good bacteria with whom we share symbiosis are an important part of our survival.

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