What is Commensalism?

• Along with mutualism, the term was coined in 1876 by Belgian palaeontologist and naturalist Pierre-Joseph van Beneden.
• Beneden first used the term to describe the behaviour of carrion-eating animals that followed predators in order to consume their leftover meal.
• The term commensalism is derived from the Latin word commensalis, which meaning “table sharing.”
• Commensalism is most frequently discussed in the realms of ecology and biology, although the term is also used in other scientific disciplines.
• Commensalism is a unique interaction between two species in biology in which one species obtains food, shelter, or transportation from the other without harming it.
• The duration of interaction between two species ranges from brief to extensive. It is a sort of symbiotic interaction; nevertheless, neither partner benefits nor suffers.
• The partner that receives the advantage is referred to as a commensal, while the other is known as a host species.
• The simplest instance of commensalism is a bird nesting in a tree. The tree offers the bird shelter and protection without being considerably injured or influenced by the bird.
• The cow egrets (birds) that feed on the insects stirred up by grazing cattle are another common example. Cattle egrets are able to obtain food without disturbing the livestock.

Types of Commensalism

Commensalism is classified as one of the following based on the objective, intensity, and duration of the relationship between commensal and host:

1. Phoresy

• Phoresy comes from the Greek word ‘phorein’, which meaning to transport.
• In phoresy, commensal organisms attach or latch onto the host solely for dispersal purposes.
• This is a brief and short-term connection.
• The relationship concludes when the commensal reaches its destination.
• The common name for the commensal is phoront.
• Typically, the phoront or commensal is a slow-moving nematode or mite.

Example of Phoresy

• Barnacles use whales for transportation, hence whales and barnacles are examples of phoresy commensalism.
• In addition, anemones adhere to the shells of hermit crabs, pseudoscorpions live on mammals, and millipedes move on birds.

2. Inquilinism

• Inquilinism is the interspecies connection in which one organism permanently inhabits or resides on another.
• The duration of this partnership is indefinite. 

Example of Inquilinism

• The woodpecker excavates a nest in the cactus.
• A bird that lives in a tree hole is an example. Some regard the growth of epiphytic plants on trees to be iniquilism, however others may view it as a parasitic connection because the epiphyte may weaken the tree or steal resources that would otherwise go to the host.

3. Metabiosis

• Metabiosis, as its name suggests, is an interspecies connection in which one species provides bios or an environment suitable to the growth and development of the other.
• In this commensalism, the host is typically a dead creature. 

Examples Metabiosis

• Bacterial development on the carcasses of the animals.
• Hermit crabs, for instance, use the shell of a deceased snail for safety. Another example would be maggots feeding on a corpse.

4. Microbiota

• In this form of commensalism, the commensals develop a community within the host. Human gut microbiota and skin microbiota are examples.
• Recent research has established the active and positive role of intestinal microbiota in the healthy life of humans, despite contradictory opinions about the classification of microbiota as a form of commensalism.
• Historically, it has been assumed that the human stomach serves as a safe haven for bacteria without hurting the host, a phenomenon known as commensalism.
• Recent research has demonstrated that gut bacteria is a source of critical amino acids and other nutrients required for human health.
• Thus, scientists are reevaluating the classification of microbiota as a sort of commensalism.

Example of Microbiota

• The bacterial flora found on human skin is one example. Scientists debate on whether or not microbiota constitutes commensalism. In the case of skin flora, for instance, there is evidence that the bacteria offer the host some protection (which would be mutualism).

Examples of Commensalism

Pseudoscorpions

• The pseudoscorpion serves as an intriguing example of commensalism. Pseudoscorpions are extremely small (less than one centimetre) scorpions that hitch rides on much larger insects.
• A pseudoscorpion is linked to a much larger fly’s leg.
• The pseudoscorpion, unlike regular scorpions, lacks a stinger and does not kill the larger insect it rides on. Frequently, it merely hitches a ride from one location to another.
• In this instance, the fly suffers just slight annoyance. The connection is terminated after the pseudoscorpion has caught a ride.
• However, if an excessive number of pseudoscorpions attempted to hitchhike, the fly would get overloaded or expend too much energy flying, and the connection would become parasitic.
• Many creatures walk a fine line between commensal and parasitic symbioses, and distinguishing between the two is frequently difficult.

Bait Fish and Manta Rays

• Small bait fish and manta rays frequently exhibit a sort of commensalism in which the baitfish are safeguarded by the larger fish’s proximity alone.
• Under the gigantic fins of large manta rays, large schools of tiny fish are frequently observed. The little fish are supposed to be shielded from birds that might otherwise dive into the water and consume them.
• In contrast, the manta ray is unaffected by the presence of the baitfish and may not even notice their presence.
• Most large marine animals are followed or attached by one or more smaller species. In certain instances, animals are parasitic, such as lampreys, which feed on their host.
• In numerous instances of commensalism, the host is unaffected. There are also fish that follow sharks and eat their leftovers.
• Others consist of little barnacles that adhere to whales so long as they do not harm the whales. Again, a certain level of commensalism is accepted without consequence, but the situation might eventually become parasitic.

Seed dispersal

• Numerous plant species have evolved peculiar mechanisms for dispersing their seeds into new settings.
• A highly effective strategy is to be sticky, barbed, or hooked. In fact, velcro was invented after scientists discovered that the seeds of harmful weeds adhered to pants.
• If you’ve ever strolled across a natural grassland, you know that your pants will be plastered with a variety of sticky seeds on the other side.
• The seeds will ultimately fall off and are harmless. Consequently, similar to the pseudoscorpion, the seeds are hitchhiking on another species.
• The host barely notices the hitchhiker and carries on without incident.
• The seeds are eventually rubbed off and have the opportunity to establish themselves in a new environment.

Other Examples of Commensalism

• Remora fish have a disc on their heads that allows them to adhere to sharks, manta rays, and whales. When the larger animal eats, the remora detaches to consume the leftover food.
• Nurse plants are larger plants that offer seedlings protection from the elements and herbivores, allowing them to grow.
• Tree frogs utilise vegetation for protection.
• Once expelled from a pack, golden jackals will follow a tiger to dine on the leftovers of its killings.
• Goby fish feed on other marine organisms, changing colour to blend in with the host to avoid predators.
• Cattle egrets consume the insects stirred up by grazing cattle. The livestock remain unharmed, whilst the birds receive nourishment.
• The burdock plant contains prickly seeds that adhere to animal fur and human clothing. The reproduction of plants depends on this mode of seed distribution, while mammals are unaffected.

References

• https://www.sciencedirect.com/topics/earth-and-planetary-sciences/commensalism
• https://www.thoughtco.com/commensalism-definition-and-examples-4114713
• https://en.wikipedia.org/wiki/Commensalism
• https://www.britannica.com/science/commensalism
• https://www.biologyonline.com/dictionary/commensalism
• https://biologydictionary.net/commensalism/
• https://www.vedantu.com/biology/commensalism
• https://blog.prepscholar.com/commensalism-examples-defintion
• https://collegedunia.com/exams/commensalism-types-examples-mutualism-parasitism-biology-articleid-679