In biology, commensalism refers to a relationship between organisms in which one species benefits and the other is neither helped nor harmed. One common type of commensalism is phoresis (a.k.a. phoresy), in which one species rides on another for a limited amount of time (if a species lives permanently on another, that's called inquilinism).

Phoresis includes burrs catching and riding in animals' fur, nematodes riding on dung beetles to reach fresh piles of dung, tardigrades catching rides on snails, and mites riding all over the place on pretty much anything. One popular example is the Bromeliad treefrog, which carries Ostracods (seed shrimp) from one bromeliad to another; the Ostracods, in turn, carry microscopic ciliates on their body, helping to intermingle a sizable chunk of the bromeliad ecosystem with each journey. Humans riding horses, camels, or elephants is sometimes claimed to be a form of phoresis, although it might better be considered a form of mutualism.

It is worth noting that a given species can have multiple types of interactions with another species, and so while one relationship might be considered phoresis (e.g., a bird carrying insect eggs to its nest) a later interaction may exhibit a different type of relationship, (e.g., the newly hatched young becoming parasites on the bird).

The species that does the riding is called a phoront or a phoretic. Both phoresis and phoresy come from the from French phorésie, with the later apparently being an attempt to coin a word unique to biology, as phoresis is also used in chemistry and physics to refer to the migration of particles through a fluid; in this context it is also used as a suffix, -phoresis, as in electrophoresis or thermophoresis.

Log in or register to write something here or to contact authors.