Egyptian plover birds don’t give a sh#tPreviously:
We’ve looked at some pretty amazing aspects of evolution so far, but where convergent evolution happens often, and badly designed organisms are common, symbiosis is quite literally all around us. In fact, some scientists even argue that the earth is essentially one giant symbiotic organism.
What is it?
As you likely know, symbiosis is a situation where two or more separate species are physically in contact with each other in a way that is beneficial for one or both members. However, this can be broken down into several categories:
• Mutualism – Classical symbiosis, where both members benefit equally
• Parasitism – Where one member actively damages or destroys the other
• Commensalism – Where one member benefits and the other has no noticeable change
• Obligate symbiosis – Where the organism requires the relationship in order to survive
• Facultative symbiosis – Not entirely necessary but it does boost chances of survival
How does symbiosis happen?
Symbiotes aren’t consciously aware of their ‘agreement’, nor do they hash out ideas in meetings to maximize their symbiotic potential. Symbiotes just do whatever they need to do, instinctively.
But how is that possible? Two creatures can’t just magically and perfectly slot together like a square block in a square whole, and then just continue generation after generation this way, so wa’ gwan with that?
‘The secret to evolution is time and death’, as Carl Sagan once put it. Over thousands of generations, two species likely start of in facultative symbiosis. This situation is pretty sweet. Addictive, even. But, like all addictions, the victims become dependent on the given benefits, and those who exploit those benefits are the ones that survive, while those who do not, die.
If that isn’t a decent argument to start taking heroin, I don’t know what is.
So it’s often just easier to use the tools of another species than figure out how to do it themselves. One example of this is the Tree-Fungi relationship. 90% of all plants in the world have a fungal partner.
Though we only see the reproductive ‘mushroom’ growing atop the ground, they are in fact a huge subterranean fungal system that latches onto the roots of trees. Fungi already has an efficient root system in place and can help the tree spread its roots further, whilst also providing nutrients. At the same time, the tree can provide a share of the nutrients created by its leafy photosynthesis.
The fine filament of a fungus greatly enhances the surface area for roots of a tree in the soilThere’s a lot of symbiosis we are plainly aware of, like our own gut bacteria; we cannot survive without it, and they need us for a nice, warm home. Like Couchsurfing.
Flowers, insects and birds often have symbiosis; the flower provides the food, the insect takes the food and also takes the pollen, dropping it off in another flower in a strange work-around sex; pollination. Birds also do this but can eat the insects if they want, too. Why not.
As shown in a previous evolution post, some flowers grow increasingly specific, allowing only a particular animal in through various mechanisms.
But there are some more bizarre and pretty outrageous. Let’s take a look.
Solar powered life
There is a worm which unfortunately lacks a popular nick name, the Symsagittifera roscoffensis, but is amazing nonetheless. Let’s call it Gitti
SourceThere are few examples better to show how in some cases, symbiosis greys the definition of what a plant and animal is.
This Gitti worm is small, flat and transparent (like your… never mind), but it takes on a green appearance after allowing algae to live and grow within its body. In return, the Gitti doesn’t even need to eat, instead surviving off the energy given by the sun, through the algae’s photosynthesis. This relationship has grown so deep, that the worm has no functioning digestive tract or mouth. What’s more, the waste products are recycled by the algae and they never need to leave Gitti’s body.
not a plantThe thing is, this isn’t even unique. Corals are animals that use algae to collect sugar, and others like sea slugs, jellyfish and sponges use this trick too. Even wilder, a few years ago the first vertebrate species was discovered running on solar power in facultative symbiosis: the spotted salamander.
Cecropia Trees and Azteca Ants
The Cecropia tree is hollow, and inside it produces sugary juice perfect for Azteca ants. The ants move into this perfect shelter and feed off the sugar. In return, the ants serve as the trees own personal army, killing off any competition in the vicinity and protecting the tree from vines and other pests and herbivores.
The tree has even developed specialised, tiny gripping hooks for the ants to use to gain greater traction during fights.
A honeyguide is a bird that LOVES honey, but it’s not strong enough to break into a hive itself. So what better way to accomplish this by deliberately grabbing the attention of bigger animals – including honey badgers and even humans – and leading them to the bee’s nest. After the stupid brute breaks it apart, the honeyguide can take its fair share.
Urchin Crab & Fire Sea Urchin
Crabs often lack sufficient defense with those measly, giant claws of death, but the Urchin crab has managed to work with a type of poisonous urchin to guarantee safety. They take a Fire Sea Urchin over twice their own size and put it on their head while they travel, and in return, the Urchin gets a free ride. This is a pretty cute video:
Frogs and spiders
In Colombia, the lesserback tarantula likes to have a frog roommate. The tarantula benefits because the frog eats the ants that would otherwise kill the eggs in the nest, and the frog benefits because it has a huge-ass tarantula protecting it.
Sloths, Moss and Sloth Moths
Try saying that three times quickly.
The three-toed sloth is a bit of a mystery. Nobody was quite sure why it would make the tedious journey down from the tree canopy just to take a poop at the base of a tree. This is super dangerous, and up to half of sloth mortality happens here.
Recently, scientists kind of figured out a three-way symbiotic relationship that could possibly make the risk worthwhile.
Originally people just thought the sloth was SO slow that even algae would grow on its back. But it’s much more than that. As it turns out, the limited diet of low-nutrition leaves is supplemented by the high-fat algae the sloth picks off its own fur.
Not only this, but the Sloth Moths help the algae grow by living and dying on it (the algae breaks down dead moths into nutrients), and the Sloth helps the Sloth Moth breed by traveling down the tree and pooping so the moths can lay their eggs there.
SourceEverybody wins. Except the sloth when it gets eaten by a jaguar, but still.