Symbiotic Relationships

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Symbiotic Relationships
relationships in which two or more organisms live
in a close and permanent association of different
species.
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Three main types of symbiotic relationships

• commensalisms- one species benefits and the other
  species is neither harmed nor benefited
• Example barnacles on a whale

http//www.cbu.edu/seisen/ExamplesOfCommensalism_
files/image002.jpg
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• mutualism- both species benefit
• Example Lichen on the trunk of a mangrove tree

http//members.optusnet.com.au/janewest000/Mangro
ve/images/lichen1.jpg
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parasitism- one organism derives benefit at the
expense of the other Example guinea worms and
humans
http//www.neatorama.com/2006/08/21/six-horrifying
-parasites/
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Question

• Name the 3 types of symbiotic relationships

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Question

• Can you give other examples of symbiotic
  relationships?

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Hermit Crabs
http//myanimalblog.files.wordpress.com/2008/03/he
rmit-crab-cove-b1.gif
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Classification

• phylum arthropoda,
• subphylum crustacean (marine hermit crabs)
• class Melacostraca
• order decapoda

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Question

• What kingdom are hermit crabs in?

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Answer

• Animalia

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Hermit crabs have a symbiotic relationship with
discarded gastropod shells
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Parts of a Hermit Crab

• Five pair of legs including a pair of claws
• The large claw is used for defense, such as
  blocking the opening from predators and
  shredding.
• The small claw is used for eating.
• The second and third pair of legs is used for
  walking.
• The last pair of legs is used for holding the
  crab in the shell.

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www.thecrabbagepatch.com/crabanatomy.html
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http//www.enchantedlearning.com/subjects/inverteb
rates/crustacean/label/hermitcrab/labelanswers.GIF
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• Hermit crabs primarily live in the wild, but are
  also very popular as pets.
• Most are marine
• Typically live in the intertidal zone

Horn Island, Barrier Island Gulf of Mexico
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Shell Facts

• they live in gastropod shells to protect
  themselves from predators
• they are scavengers
• shells are considered limiting resources
• When shells are damaged or do not fit
  appropriately hermit crabs do not have adequate
  protection and feeding and mating behavior
  suffers. They change shells

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Do hermit crabs prefer a particular kind of
shelter (shells or not)? In a study completed
by L.J. Rodrigues et al (2000), females were
significantly larger than male hermit crabs in
shells. More males where found in shells than in
tubes
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• two methods to determine shell choice
• First, was a visual preference in which a
  gastropod shell was placed next to a tube in the
  center of a plastic container.
• The second method was a chemical preference using
  chemicals extracted from snails and mixed with
  unfiltered seawater. The mixture consisted of
  .1mL of unfiltered seawater to 0.1g of snail
  tissue. Hermit crabs were placed in a Y maze
  during the chemical stimulus method. Crabs who
  were originally found in shells preferred shells
  in the visual

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Question

• Why do hermit crabs change shells?

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Question

• Can you name other types of crabs?

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Name that Crab
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Not true crabs
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References Mesce, K. (1982). Hermit crab goes
house-hunting. Science News, 121(10) p. 153 1/5
p. Rodrigues, L. J., Dunham, D. W., Coates, K.
A. (2000). Shelter preferences in the endemic
Bermudian hermit crab, calcinus verrilli
(rathbun, 1901) (decapoda,anomura)1).
Crustaceana, 73 (6) p. 737- 750. Spight, T. M.
(1977). Availability and use of shells by
intertidal hermit crabs. Biology McKenzie, N.
(1999). coenobita perlatus (Online), Animal
Diversity Web. Accessed November 29, 2008 at
http//animaldiversity.ummz.umich.edu/site/account
s/information/Coenobita_peratus.html