Biological Symbiotes

By Hannah Jeoung, Environmental Biology

Well, not quite like Venom.

As much as everyone loves this brain-eating yet cuddly alien, the kind of symbiosis that is addressed in biology is an ecological interaction. Ecological interactions are basically interactions between organisms in an environment. However, symbiotic relationships are usually specific to the interactions between two organisms. There are three main types that are emphasized in general biology: mutualism, commensalism, and parasitism.

These interspecific (across-species) interactions are often denoted by positive (+) or negative (-) symbols to signify their respective effects; for instance, mutualism (+/+), commensalism (+/0), and parasitism (+/-).

MUTUALISM

This is an example of mutualism. The clownfish protects the sea anemone and provides it nutrients, while the anemone provides a safe habitat for these fish.

The first ecological interaction that most know of is mutualism (+/+), where two species benefit from each other. One mutualistic example performed by humans is between them and E.coli bacteria, which live in the intestines. They help aid with digestion, while feeding off the nutrients that humans ingest. Another interaction is that between plant roots and fungi - known as mycorrhizae - where they each aid in the growth of the other by offering carbohydrates and phosphorus.

This creates limitations as well, however, as both plants give up needed materials to the other. Most of the time, mutualistic species can live without the aid of the other. Yet the relationship between the acacia tree and ants are an exception; the ants feed mainly on nectar produced by the plant, while the ants effectively protect the tree from animals, fungi, and the elements. Therefore, they depend exclusively on each other in order to survive.

COMMENSALISM

Hundreds of thousands of face mites - Demodex folliculorum and Demodex brevis - live, eat, and reproduce on our faces on a daily basis. Invisible to the naked eye, they spend most of their time inside the hair shafts, deep within our skin eating the oily substances produced by our face pores, sebum.

Due to the fact that they are usually nestled within our skin, it is practically impossible to remove them through washing or wiping our faces - and specialized treatments to remove them prove futile, as their populations rebound within weeks. Thankfully, the Demodex mites pose no danger to our wellbeing, and merely use our produced oils as a source of food. This kind of relationship, where one organism benefits while the other is not affected in a positive or negative way, is known as commensalism.

Commensalism (+/0), as depicted by the vivid imagery of Demodex mites, is very common in all environments. An easily recognizable interaction would be that between smaller and bigger plants in forests. The smaller plants sometimes depend on the bigger trees for shade and protection, while the latter are not affected in any way by the presence of the former. Another popular example used in textbooks are those of cattle egrets and herbivores. Egrets, a type of long-necked bird, feed upon insects that thrive in the presence of animals such as bison and cattle. Yet, they may also eat ectoparasites (parasites on animals' skin) off the larger herbivores they follow around, changing this interaction to one of mutualism. Therefore, these ecological relationships have the capacity for gradual change.

PARASITISM

Some parasites may even kill their host, laying eggs within another small species and letting their larvae hatch within an alive host before eating it from inside out - basically a smaller version of the movie Aliens.

Unlike the previous two, parasitism (+/-) is an exploitative interaction, which means one species benefits while the other is harmed. Tapeworms, often thriving in uncooked meats, are endoparasites (parasites that live within their host) that live in animal intestines. Feeding off of their host's ingested nutrients, they often grow multiple feet and may sometimes even travel to places such as the muscles and the brain.

Ectoparasites (parasites that live outside their host) include ticks and lice. Parasites can often change the behavior and survival capacity of their host, such as prompting crustaceans to move out into the open to be eaten by birds, their next intended host. Moose that are fed upon by ticks also experience weakened conditions, making it easier to be caught by predators.

Looking back, the relationship between Eddie and Venom can be related to real-life symbiosis. It may be described as a type of mutualism - Venom gets to have a host that understands him, and Eddie acquires inhuman powers to fight evil. Additionally, they both become better entities in the presence of each other.

It's definitely a +/+ interaction.

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Sources:

Urry, Lisa, et al. Campbell Biology, 11th Ed. New York, NY, Pearson Publishing Company, 2017.

https://www.livescience.com/65533-your-face-mites-never-poop.html

https://www.google.com/url?sa=i&source=images&cd=&ved=2ahUKEwjwjL3HhujiAhUXsJ4KHT5PAsEQjRx6BAgBEAU&url=https%3A%2F%2Fcomicbook.com%2Fmarvel%2F2018%2F09%2F19%2Fvenom-symbiote-spider-man-origin-changes%2F&psig=AOvVaw2x1nQWigr9aM8CjEv_4pxd&ust=1560569632438149

Photos are linked to sources.