The
University
of
the
West
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BL 1051 - Biodiversity I

Lecture 7 - Symbioses

Department
of
Biological
and
Chemical
Sciences

 

The main types of symbiosis are Parasitism, Commensalism and Mutualism.

These are points on a continuum from +/- (Parasite benefits at the expense of the host, with the extreme case of the host being killed), to +/+ (both mutualists benefit) with +/o commensalism (one partner benefits whilst the other neither suffers or gains) somewhere in between.

A second continuum deals with the degree of intimacy, e.g. predation is also a +/- relationship but does not have the intimacy of parasitism. Therefore, predation is not seen as a type of symbiosis.

The partners in any symbiosis are individuals of different species.

A third continuum runs from obligate to facultative with the extremes that neither partner can complete its lifecycle in the absence of the other to both partners can live without each other.

Parasitism

Good examples of parasitism can be found in human viruses. E.g. the common cold where the virus multiplies at the expense of the human host but the host doesn't suffer greatly and the HIV virus which causes the development of AIDS.

Commensalism

Examples include: the cattle egret (Bubulcus ibis) in the Caribbean or an epiphyte growing on a tree.

Mutualism

Examples of mutualism include: Lichens: Fungal-Algal Symbiosis and Mycorrhizas: Fungal-Plant Symbiosis as well as the cattle egret and cattle in Africa.

Phoresy

Hitch-hiking, called phoresy is by far the commonest means of dispersal employed by mites, with a wide range of other animals being used by the mites to find new homes, in some cases the mite will feed from its transport during the journey but in most cases the 'phoretic host' suffers no harm.

Flower mites travel between flowers in the nostrils of hummingbirds, e.g. Tropicoseius heliconiae.

Some invertebrates can carry an awful lot of mites, Hyatt (1959) recorded 488 Mites on a single Dor Beetle (Geotrupes stercorarius), these were:-

  • 188 Deuteronymphs of Parasitus coleoptratum

  • 147 Adult Alliphus halleri

  • 141 FemaleMachrocheles glaber

  • 5 Deuteronymphs of Parasitus intermedius

  • 4 Female Scamphis equestris

  • 3 Scarabapsis inexpectatus

 

  More WWW Links Links on this page
Symbiosis
 Information on the cattle egret, University of Michigan - Museum of Zoology
Symbiotic relationships in the rainforests
Symbiosis: mycorrhizae and lichens - A page from the University of Hawaii
Mycorrhiza information exchange
INVAM - the international collection of (vesicular) arbuscular mycorrhizal fungi
The lichen information system
The hummingbird society
Hummingbird hitchhikers
Phoretic relationships between lice and Hippoboscid flies		 Cattle egret 
Lichens: Fungal-Algal Symbiosis
Mycorrhizas: Fungal-Plant Symbiosis
Tropicoseius heliconiae.
Books to check Questions
Ahmadjian, V. and Paracer, S. (1986) Symbiosis: An introduction to biological associations. University Press of New England.
Smith, S.E. and Read, D.J. (1997) Mycorrhizal Symbiosis. Academic Press
  1. Why is the relationship between the cattle egret and cattle different in the Caribbean and Africa?
  2. What are the two commonest types of mycorrhiza? With the aid of diagrams, describe each.
  3. Construct a table comparing lichens and mycorrhizas.
  4. Is phoresy always commensalism?

 

 

Send mail to lchinnery@uwichill.edu.bb with questions or comments about this web page. Barbados lichen photo © 2003, text and design copyright © 1998-2003, L.E. Chinnery. Fish and hummingbird images from Corel Photo House which are protected by the copyright laws of the U.S., Canada and elsewhere. Used under license. Bracket fungi and rhino egret photos © 2000 Global Star Software Ltd. and its licensors. Other clip art © 1998 The Learning Company, Inc. and its licensors.
Last modified: September 26, 2004