Symbiosis and Anemones

1
  In the illustation below, you can see the anemone Adamsia sp. attached to the shell inhabited by the hermit crab Pagurus bernhardus. This is a mutualistic symbiotic relationship, as both parties benefit. The anemone gains the ability to move around, and find different prey options, instead of being stuck in one place, and the hermit crab gets protection from predators.

2

  A Lybia tesselata, or boxer crab, is shown in the illustration below holding the anemone Triactis producta in its claws. It appears to be a mutualistic relationship, as the anemone is only found with the boxer crab, but how the anemone benefits is unknown. Perhaps, as in the case above, it benefits from being carried to new sources of food by the crab.  On the other hand, the benefit to the crab is obvious, since its claws are far too small to be used for defense. So it instead keeps two smaller anemones, trimming them down to the right size, as "boxing gloves" for protection.

3
  The anemone below is  Anthopleura elegantissima, or aggregate anemone. At first glance it does not look like a symbiotic relationship is taking place, after all it is just a green sea anemone. However, the green coloration is caused by dinoflagellates and other phytoplankton, which release oxygen for the anemone. In return, the anemone grows in the photic zone so the algae have enough sunlight, and provides carbon dioxide, both of which are necessary for photosynthesis.

4
  A Stenorhynchus seticornis, or arrow crab, is commonly found living on Lebrunia neglecta (which also has a mutualistic relationship with algae), and this would seem to indicate some type of mutual relationship. This is not the case however. The arrow crab lives in the anemone's tentacles for protection, but does nothing for the anemone in return. This is called a commensalistic relationship, a type of symbiosis in which one member benefits, but neither aids or harms the other.