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17.5: Types of Commensalisms

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    Phoresis or phoresy is a non-permanent, commensalistic interaction in which one organism (a phoront or phoretic) attaches itself to another (the host) solely for the purpose of travel (White et al. 2017). Phoresis has been observed directly in ticks and mites since the 18th century (Houck and O'Connor 1991), and indirectly in fossils 320 million years old (White et al. 2017). It is not restricted to arthropods or animals; plants with seeds that disperse by attaching themselves to animals are also considered to be phoretic (Houck 2009).

    Hundreds of small, round, red mites can be seen on the wings, body, and face of a bee, even between hairs and on the eyes of the bee.

    Figure \(\PageIndex{1}\):  Male Bombus hypnorum with phoretic mites. Photograph by Dimitǎr Boevski.

    The strict definition of phoresis excludes cases in which the relationship is permanent (e.g. that of a barnacle surviving on a whale) or those in which the phoront gains any kind of advantage from the host organism (e.g. remoras attaching to sharks for transportation and food) (Houck and O'Connor 1991). Phoresis is a commensal relationship and deviations result in mutualistic or parasitic relationships. Phoretic relationships can become parasitic if a cost is inflicted upon the host, such as if the number of mites on a host begins impeding its movement. Parasitic relationships could also evolve for from phoretic ones if the phoront gains a fitness advantage from the death of a host (e.g. nutrition). Mutualistic relationships could also evolve if the phoront began to confer a benefit to the host (e.g. predator defense) (White et al. 2017). The evolutionary plasticity of phoretic relationships allow them to potentially add to the complexity and diversity of ecosystems (Houck 2009).

    Cases in which the phoront parasitizes or preys upon the host organism after travel are still considered phoresis, as long as the travel behavior and the feeding or parasitizing behavior are separate (White et al. 2017). Similarly, some pseudoscorpions prey upon the same species that act as their phoretic host. The behaviors are completely separate, however, since the pseudoscorpion uses anatomical features specifically for predation when treating the host as prey, but employs anatomical features used for phoresis when travelling (Poinar et al. 1998).



    An inquiline is an animal that lives commensally in the nest, burrow, or dwelling place of an animal of another species. For example, some organisms such as insects may live in the homes of gophers or the garages of human beings and feed on debris, fungi, and roots. The most widely distributed types of inquiline are those found in association with the nests of social insects, especially ants and termites – a single colony may support dozens of different inquiline species. The distinctions between parasites, social parasites, and inquilines are subtle, and many species may fulfill the criteria for more than one of these, as inquilines do exhibit many of the same characteristics as parasites. However, parasites are specifically not inquilines, because by definition they have a deleterious effect on the host species (Nash and Boomsma 2008), while inquilines have not been confirmed to do so.

    In the specific case of termites, the term "inquiline" is restricted to termite species that inhabit other termite species' nests (Florencio et al. 2013; Cunha et al. 2003; Hugo et al. 2019), whereas other arthropods cohabiting termitaria are called "termitophiles" (Rosa et al. 2018; Oliveira 2018). It is important to reiterate that inquilinism in termites (Blattodea, formerly Isoptera) contrasts with the inquilinism observed in other eusocial insects such as ants and bees (Hymenoptera), even though the term "inquiline" has been adopted in both cases. A major distinction is that, while in the former the species mostly resemble forms of commensalism, the latter includes species currently confirmed as social parasites, thus, being closely related to parasitism.

    Inquilines are known especially among the gall wasps (Cynipidae family). In the sub-family Synerginae, this mode of life predominates. These insects are similar in structure to the true gall-inducing wasp but do not produce galls, instead, they deposit their eggs within those of other species. They infest certain species of galls, such as those of the blackberry and some oak galls, in large numbers, and sometimes more than one kind occur in a single gall. Perhaps the most remarkable feature of these inquilines is their frequent close resemblance to the insect that produces the gall they infest (Rines 2020; Discover Life 2011).

    The term inquiline has also been applied to aquatic invertebrates that spend all or part of their life cycles in phytotelmata, water-filled structures produced by plants (Cronk and Fennessy 2001). For example, Wyeomyia smithiiMetriocnemus knabi, and Habrotrocha rosa are three invertebrates that make up part of the microecosystem within the pitchers of Sarracenia purpurea (Cochran-Stafira and von Ende 1998). Some species of pitcher plants like the Nepenthes and Cephalotus produce acidic, toxic or digestive fluids and host a limited diversity of inquilines. Other pitcher plant species like the Sarracenia or Heliamphora host diverse organisms and depend to a large extent on their symbionts for prey utilization (Adkassnig et al. 2011).

    A photo from a microscope of a long microorganism with hairlike structures.

    Figure \(\PageIndex{2}\):  Wyeomyia smithii larva is an inquiline species in the pitcher leaves of Sarracenia purpurea.  "Wyeomyia smithii" by Rkitko is licensed under CC BY-SA 3.0.   


    Metabiosis is a more indirect dependency, in which one organism creates or prepares a suitable environment for a second. Examples include maggots, which develop on and infest corpses, and hermit crabs, which use gastropod shells to protect their bodies.



    Adlassnig, W., Peroutka, M., & Lendl, T. (2011). Traps of carnivorous pitcher plants as a habitat: Composition of the fluid, biodiversity and mutualistic activities. Annals Of Botany, 107(2).

    Cochran-Stafira, D.L., & von Ende, C.N. (1998). Integrating bacteria into food webs: Studies with Sarracenia purpurea inquilines. Ecology, 79(3), pp. 880–898.

    Cunha, H.F.D., Andrade Costa, D., Espirito Santo Filho, K.D., Silva, L.O., & Brandão, D. (2003). Relationship between Constrictotermes cyphergaster and inquiline termites in the Cerrado (Isoptera: Termitidae). Sociobiology, 42(3), pp. 761-770.

    Cronk, J.K., & Fennessy, M.S. (2001).Wetland plants: Biology and ecology, p. 45.

    Discover Life: Family Cynipidae: Subfamily Synerginae visited 1 January 2011

    Florencio, D.F., Marins, A., Rosa, C.S., Cristaldo, P.F., Araújo, A.P.A., Silva, I.R., & DeSouza, O. (2013). Diet segregation between cohabiting builder and inquiline termine species. PLOS ONE, 8(6), Bibcode:2013PLoSO...866535Fdoi:10.1371/journal.pone.0066535PMC 3689842PMID 23805229.

    Houck, M.A., & O'Connor, B.M. (1991). Ecoological and evolutionary significance of Phoresy in the Astigmata. Annual Review of Entomology, 36(1), pp. 611–636. doi:10.1146/annurev.en.36.010191.003143ISSN 0066-4170.

    Houck, M.A. (2009). Phoresy, encyclopedia of insects. Elesvier, pp. 772-774. doi:10.1016/b978-0-12-374144-8.00205-8ISBN 9780123741448, retrieved 2018-10-14

    Hugo, H., Cristaldo, P. F., & DeSouza, O. (2019). Peaceful behaviour: A strategy employed by an obligate nest invader to avoid conflict with its host species. bioRxiv, 587592.

    Nash, D.R., & Boomsma, J.J. (2008). Communication between hosts and social parasites. In D'Ettore, P., & Hughes, D.P. (Eds.), Sociobiology of communication: An interdisciplinary perspective , pp. 1-55, e80. Oxford: Oxford University Press.

    Oliveira, M.H., Da Silva Vieira, R.V., Moreira, I.E., Pires-Silva, C.M., De Lima, H.V.G., De Lima Andrade, M.R., & Bezerra-Gusmão, M.A. (2018). The road to reproduction: Foraging trails of Constrictotermes cyphergaster (Termitidae: Nasutitermitinae) as maternities for Staphylinidae beetles. Sociobiology, 65(3), pp. 531-533.

    Poinar Jr., G.O., Curcic, B.P.M., & Cokendolpher, J.C. (1998). Arthropod Phoresy involving pseudoscorpions in the past and presentActa Arachnologica, 47(2), pp. 79–96. doi:10.2476/a

    Rines, G.E. (1920). Inquiline. Encyclopedia Americana.

    Rosa, C.S., Cristaldo, P.F., Florencio, D.F., Marins, A., Lima, E.R. & DeSouza, O. (2018). On the chemical disguise of a physogastric termitophilous rove beetle. Sociobiology, 65, pp. 38-47.

    White, P., Morran, L., & de Roode, J. (2017). Phoresy. Current Biology, 27(12), R578-R580. doi:10.1016/j.cub.2017.03.073PMC 5749251PMID 28633022.


    Contributors and Attributions

    This chapter was written by Aaron Howard with text taken from the following CC-BY resources: 

    17.5: Types of Commensalisms is shared under a CC BY-NC-SA license and was authored, remixed, and/or curated by LibreTexts.