By Mary K. Wicksten - Texas A&M University
September 22, 2015
A deepwater hermit crab using an anemone as a shell was spotted during Dive 08. Image courtesy of the NOAA Office of Ocean Exploration and Research, 2015 Hohonu Moana. Download larger version (jpg, 1.4 MB).
Hermit crabs are unusual in having a soft posterior region, the abdomen, hidden within a snail shell or other covering. A hermit crab must change shells throughout its life as it grows: that is, unless it is a deepwater hermit crab, family Parapaguridae.
Members of this family have a very strange association with a sea anemone, family Hormathiidae. The crab starts out inhabiting a shell. The sea anemone settles on the shell and then overgrows it, eventually dissolving the shell and forming a covering that expands as the crab grows.
This arrangement is useful for both the crab and the anemone. Experiments on shallow-water crabs indicate that the stinging tentacles of the anemone repel octopods. The anemone, in turn, gets free transportation.
