Commensalism

 The word "commensalism" is derived from the word "commensal", meaning "eating at the same table". The term was coined in 1876 by Belgian paleontologist and zoologist Pierre-Joseph van Beneden,

Commensalism is a type of relationship between two living organisms in which one organism benefits from the other without harming it. A commensal species benefits from another species by obtaining locomotion, shelter, food, or support from the host species, which (for the most part) neither benefits nor is harmed. The species that gains the benefit is called the commensal. The other species is termed the host species.

Examples of Commensalism

Remora fish have a disk on their heads that makes them able to attach to larger animals, such as sharks, mantas, and whales. When the larger animal feeds, the remora detaches itself to eat the extra food.

 

Remora are small fish that have a sucker-like disk on their heads that allows them to attach to other animals. Remora will use the sucker to attach to sharks, rays, turtles, whales, or other large marine animals. The remora benefits by getting to travel to new food and breeding areas without expending energy for travel and while being protected by the larger animal. The remora also benefits in another, somewhat grosser, way: its diet is made primarily of its host’s feces, so it has ample access to food while hitching a ride. Its carrier is unaffected because the sucker doesn’t harm or help it and the remora is small enough not to impede its movement or speed.

 

 

Figure : Commensalism cattle egrets on grazing cattle

·       Another typical example of commensalism is the cattle egrets (birds) that feed upon the insects stirred up by the feeding cattle. Cattle egrets get their food without disturbing the grazing cattle. ·       In these interactions, the cattle are unaffected, while the birds gain food.

 

 

 

Sea anemones and colorful clownfish also exhibit commensalism. Clownfish take shelter in the sea anemone to protect themselves from predators. In the adaptation process, clownfish develop a mucous coating around themselves, allowing them to take refuge in the sea anemone without affecting its stings. Also, clownfish feed upon the debris of the last meal of sea anemones, thus keeping them clean.

Domestic dogs, cats, and other animals appear to have started out with commensal relationships with humans.

Types of Commensalism (With Examples)

Inquilinism - In inquilinism, one organism uses another for permanent housing. An example is a bird that lives in a tree hole. Sometimes epiphytic plants growing on trees are considered iniquilism, while others might consider this to be a parasitic relationship because the epiphyte might weaken the tree or take nutrients that would otherwise go to the host. An example is a woodpecker drilling a cavity in a saguaro cactus to use as a nesting site. The woodpecker benefits; the cactus is unaffected.

 

Metabiosis - Metabiosis is a commensalism relationship in which one organism forms a habitat for another. An example is a hermit crab, which uses a shell from a dead gastropod for protection. Another example would be maggots living on a dead organism. Metabiosis is when an organism (often deceased) creates an environment for another organism, such as bacteria growing in the remains of a dead animal. The deceased animal, because it is dead, can’t be harmed or benefited, but the bacteria get a habitat and food source.

 

Phoresy - In phoresy, one animal attaches to another for transport. This type of commensalism is most often seen in arthropods, such as mites living on insects. Other examples include anemone attachment to hermit crab shells, pseudoscorpions living on mammals, and millipedes traveling on birds. Phoresy may be either obligate or facultative.

 

Microbiota - Microbiota is commensal organisms that form communities within a host organism. In this commensalism, the commensals grow inside the host to form a community. An example is the gut or skin microbiota in humans. Although there are conflicting views regarding classifying microbiota as a type of commensalism, recent studies have confirmed intestinal microbiota’s active and beneficial role in the healthy life of human beings. Historically, it is believed that the human gut provides shelter to the microbes without affecting the host human and is thus categorized as commensalism. However, recent studies have proven that gut microbiota is a source of essential amino acids and other nutrients required for the healthy life of humans. Thus, the classification of microbiota as a type of commensalism is under review by scientists