18: Symbiosis- living together

The world is a very interconnected space and everything is somehow affected by the things around it. This can be on the atomic level, with the existence of pretty much everything being dependent on forces of attraction holding together the atoms that make up fire, fingers and fruit teas. It can also be on the physical level with rain and snow eroding rocks, and rocks directing the flow of snow and rain as rivers and glaciers. Of course, living things are also completely dependent on interactions with the non-living environment and with one another (for more of an overview see plog post 1: Ecology, and how wolves can move a river). This week we will be digging a little deeper into some of the types of relationships between different forms of life, a topic that is known as symbiosis (readers, this is where I cue ‘The Circle of life music’ as a Simba pun and because it’s reasonably relevant!).

A buffalo giving a piggy back to some nit nibbling birds. They remove annoying creepy crawlies from the buffalo’s back and in return get a meal

What is symbiosis

Symbiosis, from the Greek for ‘living together’ is a long term interaction between two organisms. They can be of the same species, different species, and even be species living inside or attached to species, but doesn’t include random rare encounters. As with any interactions, they can be good, bad or somewhere in between. Below I’ll explore four main types of symbiotic relationships in an Arctic context, though of course they happen outside the Arctic in many situations too.

Mutualism

Mutualism is a symbiotic relationship where both organisms get a benefit out of working together. An example is the Arctic Poppy and the Arctic Bumblebee. The Arctic Poppy produces nectar which the bee eats. As the bee is busy reaching into the flower to get the nectar, the poppy puts pollen (basically flower sperm) onto the furry back of the bee. Then when the bee flies off to another poppy to drink its nectar, it carries the pollen with it. This is then transferred to the new flowers whilst the bee is once again reaching for nectar, and the flower is fertilised. This way the bee gets lots of free food (and who doesn’t love free food), whilst the plants who can’t move to one another still manage to make lots of plant babies. It’s a win-win situation!

Another example is gut microbes and reindeer. Reindeer eat many very tough kinds of foods like woody shrubs, which they struggle to digest on their own. However in their intestines they have microbes which can break down and reach the nutrients in these woody plants. As they do this they secrete some of it into the intestines which the reindeer can then absorb and use. So the microbes sit happily in the gut getting food supplied to them by the reindeer, whilst the reindeer get the microbes to actually break down this food and hand over some of the nutrients which they otherwise wouldn’t be able to get. This is an essential part of reindeer digestion, but it also does go on in human guts too. That’s right, you partly live off microbe waste in your gut.

An Arctic Bumblebee pollinating an Arctic poppy (Picture: tundrabiome blog)

Commensalism

Not all relationships are entirely good. In commensalism, one organism benefits from the interaction, whilst the other isn’t really affected. An example of this is reindeer and Arctic foxes. Reindeer often have to dig through snow in wintertime to reach food like lichens on the ground. Once they have finished digging and have wandered off, Arctic foxes can dig a little deeper into these holes to reach their prey species like lemmings which also live under the snow. The Arctic foxes benefit, because they have to use less energy to reach their lemming dinner, but the reindeer isn’t really affected positively or negatively by the relationship.

An even simpler example is when ptarmigan, grouse-like birds, take shelter behind shrubs in cold snowy weather or even to hide from predators. The ptarmigan gets shelter which is good for it, but this interaction doesn’t make any difference to the shrub.

Arctic foxes can find it useful to stay near reindeer in wintertime (Picture: Kjetil Schjølberg )

Parasitism

This one needs little explaining. Parasitism is when one organism known as the parasite benefits, whilst the one being parasitized (also known as the host) definitely does not benefit, sometime not-benefitting so much that it dies in the process. A classic example of this is the tapeworm. All kinds of mammals in the Arctic like musk oxen, reindeer and wolves can be hosts to tapeworms, as can species all over the world. The tapeworms develop inside of the host and start to eat the food that their host has eaten, using up all the nutrients themselves. This means that the host doesn’t get the nutrients, so can end up becoming malnourished or even starving to death despite eating. Tapeworm gets free food, host wolf starves, so a definite win-lose situation.

Less deadly but still parasitic are mosquitoes, which benefit from drinking the blood of creatures wandering around on the tundra, humans included. They get food, whilst the blood provider is slightly weakened and probably rather irritated.

A mosquito after having extracted it’s blood meal. I’m sorry… I realise you probably don’t want to look at that… (Picture: Getty Images/iStockphoto)

Mimicry and predator-prey relationships

Those three are the main symbiotic relationships. There are other categories of interactions which could be seen as symbiosis too. One example is mimicry, when a non-dangerous species looks like a dangerous species so others think it is dangerous and don’t attack it. Robber flies, a harmless type of fly, look a lot like wasps. As they look like wasps, many creatures mistake them for wasps, fearing the sting, so leave them alone. This benefits the robber fly, though the wasp itself isn’t actually interacting in this situation other than having a stingy reputation. Another example is predator-prey relationships. Lynx hunt snowshoe hares. This interaction give the lynx food, which it likes, whilst it gives the hare death, which it does not like. This is in many ways similar to parasitism, but is still classed as a slightly different kind of interaction.

The robber fly which, if you didn’t look too closely and it flew at your face you could mistake for a wasp

As you can see life on earth is based on a bunch of different interactions, and humans aren’t exempt from this. Dogs benefit from human food whilst we benefit from their sled pulling skills (mutualism), seagulls (or in the case of Alaska massive eagles) benefit from our food trash whilst we’re largely unaffected by them (commensalism), and humans are able to get tapeworms too (parasitism). Life on earth is intricately interconnected so whilst many things affect us, we also affect the creatures and environment around us too, for better and for worse.

For more info:

For more examples of different symbiotic relationships: https://biologydictionary.net/symbiosis/

Music from: kongano.com

Title picture from wired.com

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