Introduction
Among the best known variants of symbiosis, commensalism plays a cardinal role: we are talking about a relationship established between two living organisms - known as diners - in which a protagonist of the relationship benefits from it, while the other does not benefit from any benefit, nor is he damaged in any way. Many diners belonging to different species peacefully occupy the same place, without damaging the other components: for this reason, commensalism is often referred to tenancy.
Commensalism is a "very important form of correlation between different species: just think, for example, of all those organisms which, by nature, are too fragile or weak to fearlessly face their adversaries alone. Thus, only by finding refuge in organisms of another nature can take shelter, while not causing damage to the individual who hosts them: a classic example is represented by the birds that find refuge in the hollows of the trees.
Diner
The "commensal appellation derives from the English term"commensal"which, literally, means sharing food, an expression in any case referring to human relationships; the commensal Anglo-Saxon, it derives, in turn, from the Latin term cum-mensal which, translated, refers to a "sharing of the table / canteen", referring to the sharing of the same food between animals of different species. Originally, the word commensal was used exclusively to describe the use of the scraps of some animals (or their carcasses) from other species, after the predators had finished their meal.
Commensalism classification
There are several forms of commensalism:
- Tenancy: one organism uses another to live there.An example is epiphytic plants (like many orchids) that grow on trees, or birds that live in hollows in trees.
- Metabiosis: it is a rather complex form of commensalism, indirect, in which an organism uses what a second organism has originated, following its death.
- Foresi: the commensalism is in this case aimed at the transport of an animal by means of another, typical is the commensalism between mites and insects / birds: the mite, lying on bees, butterflies or other animals, is transported from one place to another. "other, however, causing no harm to the guest."
Insights
The boundary between commensalism, tenancy, mutualism and other symbionic variants is often extremely thin, so much so that it often creates confusion between the various terms.
In all likelihood, the commensal organism that sneaks into the (larger) guest will not leave it for life, at least not spontaneously: in doing so, the small diner permanently binds its fate to those of the guest. In this case we speak of tenancy. When the little diner dies, the guest could take advantage of it, feeding on the remains of the partner: here, therefore, the initially tenant relationship turns into a sort of parasitism.
Furthermore, it is difficult to define with certainty whether the symbiosis between intestinal bacteria and man can be defined as a form of symbiotic mutualism or commensalism.
