What is commensalism?

We explain what commensalism is and its differences with mutualism. In addition, examples and how it develops in the desert.

1. What is commensalism?

Commensalism is known as a specific type of interspecific biological interaction, that is, of interaction between individuals of different species , characterized by the benefit of only one of those involved , without the other party receiving any type of damage or harm.

The term commensalism comes from the Latin cum mess, which translates as “sharing the table” , and was originally used for those cases in which one animal fed on the remains of another’s food, as do scavengers , which they expect for the hunter to finish feeding. However, there are many other cases that can be understood as commensalism, such as:

• Foresis It occurs when the diner uses another species to transport from one place to another.
• Tenant In this case the diner finds lodging in the member of the other species.
• Metabiosis or tanatocresia. The diner takes advantage of the droppings, remains or bodies of another species to protect, reproduce or help in some way.

2. Commensalism and mutualism

Unlike commensalism, in which a single species of those involved benefits, in the case of mutualism it is both species that benefit from their interaction . This type of case is typical among species that have compatible biological characteristics, and can be fed in a positive way, that is, mutually beneficial.

This is the case, to cite an example, of mycorrhizae: fungi that make life between the roots of certain trees, exchanging with them nutrients and organic matter (used by the fungus) in exchange for water (usable by the roots of the tree). Both organizations benefit.

3. Examples of commensalism

Some common examples of commensalism are:

• The remoras. Small saltwater fish capable of adhering to animals of greater size and greater strength, such as sharks, to take advantage of their ability to swim quickly and move from one place to another quickly.
• The sea acorns. A genus of immobile marine crustaceans , they make life on the shells of mussels, oysters and other bivalves, as tenants.
• The hermit crabs. With a soft abdomen, they take advantage of the empty shells of marine snails to enter and protect themselves, as if it were their own.
• Certain species of epiphytic plants, not parasites. They live on the branches of large trees, thus accessing levels of sunlight that are scarcer at ground level .

4. Desert Commensalism

The desert habitat is one of the most extreme in the world and its flora and fauna is adapted to its difficult climatic conditions. This does not prevent them from forming commensalism relationships, although they certainly occur less frequently than in other friendlier environments . Examples of this are as follows:

• Burrows dug underground by rodents are often abandoned, and then other species can inhabit them and run away from the sun, as certain types of snakes and scorpions do.
• The owls and owls of the desert take refuge in holes made by other species within the cacti, having their young there and gaining protection from the sun and other species.
• The birds of prey are common in the desert, as certain species of vulture, and feed any organic residue product hunting larger species.

5. Other types of interspecific relationships

In addition to commensalism and mutualism, of which we have already spoken, there are the following types of interspecific relationships:

• Parasitism . It occurs when one species benefits from the other nutritionally or otherwise, that is, it benefits from it, but in this case causing damage of some kind. A perfect example of this is mosquitoes, which feed on the blood of animals to incubate their eggs, and can in turn transmit diseases to which it serves as a contagion agent.
• Symbiosis. It is a very narrow degree of mutualism, in which the species involved end up becoming codependent, that is, needing the presence of the other to survive or to complete their life cycles. A good example of this is the relationship between an algae and a fungus to form a lichen, exchanging structure for moisture and nutrients.
• Competition. Quite the opposite of commensalism, occurs when two species compete or face each other for access to the resources necessary to survive, so that only one of them can benefit. This is the case, for example, of the competition between hyenas and vultures, or other African scavengers, for devouring the remains of the lion hunt.
• Predation The fundamental type of interaction in the trophic chain is that one species (the predator) hunts and devours another (the prey ), thus obtaining a nutritional benefit and ending the existence of the other. It is what happens when a fox hunts a rabbit and devours it.
• Amensalism. In this case the interaction between the species is detrimental to one of them, without the other obtaining in return any kind of benefit. This is the case with trees such as Eucalyptus or Walnut, for example, that prevent the growth of other plant species around them, without directly benefiting from the process.