This document defines and provides examples of different types of commensalism. Commensalism is an ecological interaction where one species benefits while the other is unaffected. It defines the key terms and discusses four main types of commensalism: inquilinism, where one species lives in or on the body of another; metabiosis, where a commensal uses remains or waste of the host; phoresy, where a commensal hitches a ride on a host for dispersal; and microbiota, groups of microbes that colonize host surfaces. Examples provided include flies laying eggs in dung balls rolled by beetles, hermit crabs using gastropod shells, nematodes hitching

1. Commensalism
Dr. P. Suganya
Assistant Professor
Department of Biotechnology
Sri Kaliswari College (Autonomous)

2. Definition
 Commensalism is a type of ecological interaction
between two or more species where one of the
species is benefitted without either harming or
benefitting the other.
 Commensalism is a positive interaction but is quite
different interactions like mutualism or parasitism.
 It is usually a long term relationship where some
species remain in the interaction for their entire life.
 The interaction mostly exists between a larger host
and a smaller commensal. The organisms that
provide the benefit but are unaffected is the host and
the organism which is benefitted from the interaction
is the commensal.
 The commensal might even demonstrate different
forms of structural and functional adaptation based
on the relationship.

3.  The term commensalism is derived from the
term ‘commensal’ which means eating at the
same table. The term was popularized in
ecology by Pierre-Joseph van Beneden in
1876.
 The benefits obtained by the commensal
from the interaction can either be services
like transportation, protection, or resources
like nutrients.
 Commensalism, like most ecological
interaction, has played essential roles in
evolution as the interactions and adaptations
accumulate over time.
 This form of interaction can exist between the
organisms of the same species or different
species.

5. Types of Commensalism
 Commensalism is of different types
depending on the strength and duration of the
interaction and the purposes.
1. Inquilinism
 Inquilinism is a type of commensalism where
one of the species uses the body or a cavity
with the body of the other organisms as a
living.
 In this form of commensalism, one of the
species is benefitted as it attains shelter while
the other species remain unaffected.
 Inquilinism exhibits resource commensalism
where the commensal attains a resource in
the form of shelter.

6. Example- Scarab beetles and
flies
 Scarab beetles roll balls of dung which they then
bury underground in burrows as a food source
for their immatures. When they roll the ball, small
flies are attracted to the dung.
 The adult flies lay their eggs in the ball and
escape from the burrow before the beetles seal
the holes.
 The fly larvae in the ball share the dung with the
beetles’ larvae without negatively impacting the
host.
 The larvae beetles then develop into adult
beetles and dig out of the burrow while releasing
the adult flies.
 Thus, the species exist in a commensal
relationship for a short period of time, and the
interaction is essential for the lifecycle of the

8. 2. Metabiosis
 Metabiosis is a form of commensalism
where the host species unintentionally
creates a suitable environment for the
commensal.
 In metabiosis, most commensal use the
remains of some part of the remains of
the host for their benefit.
 The commensal might use the remains
of the host as tools for their survival or as
a form of protection.
 The host species involved in this form of
interaction are usually large, whereas the
commensals are small.

9. Example- Hermit crabs and
gastropod shell
 Hermit crabs live inside the empty gastropod
shell to protect their soft abdominal exoskeleton.
 The shell protects the animals against predation,
desiccation, thermal and osmotic stress. Hermits
continuously evolve to rapidly access good
quality shells through competitive interactions
with other individuals and aggregation.
 Some of the hermit crabs also carry the shells
around with them as portable homes which also
protect the organisms against predation and
other conditions.
 The ability of hermit crabs to utilize gastropod
shells as a form of living space is due to the
availability of different shapes and sizes of shells.

11. 3. Phoresy
 Phoresy is a form of interaction between two species
where the commensal or phoront latches onto the host
animals for dispersal without inducing parasitism.
 The term phoresy is derived from the Greek word ‘phorein’
meaning ‘to carry’.
 In a typical interaction, the phoront or phoretic organisms
is an animal usually a nematode or mite, with the ability to
travel limit distances and thus, requires aid in dispersal
with the help of a mobile host.
 The benefit obtained by the phoront is measured in terms
of dispersal instead of nutritional benefits, like in the case
of parasitism.
 Phoresy is a temporary interaction that continues only until
the phoront reaches the desired distance. The interaction
can, however, turn parasitic over time.
 Phoretic interactions exist between species of the entire
animal kingdom and thus are extremely diverse.

12. Example-
Caenorhabditis remanei (soil
nematode) and molluscs
 Caenorhabditis remanei is a soil nematode
that has a limited dispersal ability on its own
due to the small size and sensitivity to
desiccation.
 The species thus depends on other animals
like slugs, snails, and isopods for dispersal to
longer distances.
 The interactions are strictly used for dispersal
and to avoid harsh environmental conditions.
 Most of the species remain on the body of the
slugs, but in some cases, the organisms can
be found within the intestine of the slugs.

14. 4. Microbiota
 Microbiota is a group of microorganisms that exist
in a commensal interaction with the host surface as
they colonize a particular tissue surface.
 The system formed is termed normal microbiota,
and it mostly comprises bacteria with few fungi,
protozoans, and viruses.
 These species exist in a commensal relationship
with the host species and depend on the host for
nutrition and living space.
 Even though the population of a microbiota
develops in close parallel with the host, they do not
cause harm to the host body.
 However, in some cases, in individuals with
reduced immunity and immune-compromised
conditions, these species might cause different
diseases.

15. Example- Gut microbiota in
human
 In humans, a large group of microorganisms
resides in different parts of the body, but the most
diverse and the largest population of such
organisms reside in the gut.
 These microbes exist on the surface of human
tissue and depend on the host for nutrients and
living space.
 Even though the microorganisms take up
nutrients from the digestive system, it doesn’t
cause any harm to the host unless the species is
pathogenic.
 In some cases, the species might be
opportunistic pathogens and cause diseases in
immunocompromised individuals.

17. References
 https://microbenotes.com/commensalism/
 (2008) Commensalism. In: Capinera J.L.
(eds) Encyclopedia of Entomology. Springer,
Dordrecht. https://doi.org/10.1007/978-1-
4020-6359-6_775
 White, P Signe et al. “Phoresy.” Current
biology: CB vol. 27,12 (2017): R578-R580.
doi:10.1016/j.cub.2017.03.073
 Sourakov A. (2008) Inquilines and
Cleptoparasites. In: Capinera J.L. (eds)
Encyclopedia of Entomology. Springer,
Dordrecht. https://doi.org/10.1007/978-1-
4020-6359-6_1536

18. THANK YOU