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Mutualism hot buttons for symbiosis topics in BCCR hot button for commensalism part of BCCR hot button for symbiosis quizzes part of BCCR hot button for mutualism part of BCCR hot button for parasitism part of BCCR
Mutualism is a symbiotic relationship where both partners benefit. Other types of symbioses are accessible via the icons. After viewing these 3 topics, you can test your knowlege by taking the symbiosis quizzes.

Other types of mutualisms

  This section deals with other types of mutualisms; that is, types other than ZOOXANTHELLA-TYPE MUTUALISMS and CLEANERS & CLEANING STATIONS, which can be found elsewhere.
  photo collage of orange-icing sponges on mound coralsOrange-icing sponges Mycale laevis live in association with corals. The interaction is thought to be mutualistic in that the sponge is provided a clean, solid substratum on which to grow, while the coral is provided secondary protection by the sponge‚Äôs chemical defenses. In fact, studies in Key Largo, Florida show that larvae of orange-icing sponges are no more likely to settle in association with corals than on other surfaces such as rubble and even other sponges, and that the sponge itself is actually chemically undefended. In fact, it is readily eaten by spongivorous fishes unless found in association with live corals. Instead, the authors suggest that the association results from decreased predation on Mycale larvae that settle on the corals, and it is the sponges that are benefitting from chemical protection offered by the corals, not the other way round. If this is true, the sponges are acting more like parasites than mutuals. Loh & Pawlik 2012 Invert Biol 131(3): 155.

photograph of parasitic zoanthid on a vase sponge
Zoanthids are commonly found on certain sponges and, while the species name "parasiticus" of the particular zoanthid shown here is quite suggestive, it is actually unclear whether the relationship is mutualistic or parasitic. For more information on zoanthids and their sponge hosts see SYMBIOSES: PARASITISM.





Sponge zoanthid Parazoanthus parasiticus growing
on a pink-vase sponge Niphates digitalis 0.75X


photograph of goby symbiotic with shrimp
Certain species of gobies live as mutuals with snapping shrimps Alpheus spp. in burrows excavated by the shrimps. The goby benefits from the burrow's protection, while the shrimp benefits from the sharing of food scraps obtained by the goby and by the goby's watchfulness for predators. The relationship may have started facultatively, with gobies entering shrimps' burrows in search of a protective hole, then only later evolved into an obligatory symbiosis. Karplus et al. 1972 Mar Biol 17: 275.


Goby with Alpheus sp. shrimp
at their burrow opening



photograph of snapping shrimp Alpheus with one of its anemone hosts
Snapping shrimps like to live within the tentacles of certain sea anemones. The relationship is mutualistic in that the shrimps appear to chase off predators while benefitting from the protection conferred by their hosts' stinging cells. Interestingly, when the intruder is a predatory bristleworm, the shrimp's aggressiveness seems to be limited to snapping, rather than biting, with its claws. Smith 1977 Bull Mar Sci 27: 343.




Snapping shrimps Alpheus armatus associate with a variety of sea
anemones, in this case, the hidden anemone Lubrunia coralligens 1.5X


photo collage of banded-clinging crabs in their host sea anemones
In return for protection provided to banded-clinging crabs Mithrax sp. living in its tentacles, a host sea anemone such as the giant anemone Condylactis gigantea may benefit from food scraps gathered by the crabs.

In indo-Pacific coral reefs a coral/sea anemon-inhabiting crab Trapezia sp. defends its host by nipping at polyp-eating fishes. Trapezia's presence in some species of Pacific corals is known to encourage its host to produce a type of fatty extrusion that is then eaten by the crabs.

  photo collage of cleaner shrimps in their sea anemones
Several types of shrimps, some of them cleaning shrimps, live amongst the tentacles of sea anemones but are not stung by their host's nematocysts. The shrimps presumably benefit from the protection provided by their hosts, while the anemones may benefit from food bits gained adventitiously form the shrimps on their return from foraging expeditions; thus, the relationship is a mutualism.

Or is it? Studies on an Indo-Pacific Periclimenes/anemone association, in which host anemones are kept for a 30d period with and without Periclimenes, and with and without brine shrimps being provided as food, some unexpected results are obtained. Here is the treatment array showing the condition of each set of anemones at the end of the 30d experimental period:
Study by Fautin et al. 1995 Mar Ecol Prog Ser 129: 77.

NOTE both participants, shrimps and sea anemones, eat brine shrimps Artemia salina. Note also in the 2nd and 4th treatments with Periclimenes present that it actively clips the tentacles from the sea anemone and mostly eats them. It clips less in the 4th treatment where brine-shrimp food is also present

drawing 1 in a series of 4 showing treatment in one part of shrimp/anemone study drawing 1 in a series of 4 showing treatment in one part of shrimp/anemone study drawing 1 in a series of 4 showing treatment in one part of shrimp/anemone study drawing 1 in a series of 4 showing treatment in one part of shrimp/anemone study shrimp Periclimenes brine-shrimp food

...shrimp Periclimenes is present brine-shrimp food shrimp Periclimenes
..brine-shrimp food is present
...shrimp Periclimenes is present
..brine-shrimp food is present

Well, the results seem quite straightforward and you've probably come to some conclusions on your own. However, to ensure a clear understanding of the 3 main symbiotic relationships and also of the experimental results, take the time to identify the 2 true statements from the following list. Then CLICK HERE for explanations.

The relationship is a mutualism.

The relationship is a commensalism.

The relationship is a parasitism.

The sea anemone is an obligate symbiont, i.e., requires the presence of the shrimp Periclimenes to survive.

The sea anemone is a facultative symbiont, i.e., can survive in the absence of the shrimp Periclimenes.

The Periclimenes shrimp is an obligate symbiont, i.e., requires the presence of the sea anemone to survive.

The Periclimenes shrimp is a predator of the sea anemone.

  photograph of rope sponges courtesy Anne Dupont, Florida
Different species of rope sponges such as Niphates erecta (lavender), Aplysina cauliformis (row pore), and perhaps others, often grow intertwined, and their association may be so intimate as to suggest mutual benefit. Photographs courtesy Anne Dupont, Florida.

But what could be the mutual benefits for rope sponges growing intertwined in this way? Think about the answers provided below then CLICK HERE for explanations. Observations from Wulff 1997 Ecology 78: 146.

They resist environmental stresses better.

They share nutrients.

They are actually just colour morphs of the same species; hence, not mutuals.


hot button for commensalism part of Biology of Caribbean Coral Reefs website hot button for parasitism part of Biology of Caribbean Coral Reefs website hot button for mutualism part of Biology of Caribbean Coral Reefs website