"Home is where the shell is"
Hermit crabs are interesting creatures. They are part of the crustaceans in phylum Arthropoda along with lobsters, shrimp, and many more. There are approximately 1100 species of the hermit crab. Most of them need a shell to protect their vulnerable bodies unlike normal crabs. The following is a labelled picture of the crab parts, most of which we learned about yesterday.
All Arthropods have an exoskeleton that protects their bodies. The exoskeleton does not grow with the arthropod, it molts and then the animal finds/grows a new one. This can be compared to humans who have an endoskeleton that grows with us. These crustaceans use snail shells as their exoskeleton. They often compete with each other for shells. Sometimes a crab will have a mutual relationship with a sea anemone that helps it camoflage. The anemone gets to travel with the crab and usually transfers to the different shells the crab adopts. Some might use pieces of bamboo or a coconut shell when snail shells are scarce or hard to come by. Some crabs will eat their old shell for the nutrition.
The shell of a large land snail (probablyHelix pomatia) with parts broken off to show the interior structure.
1 - umbilicus
2 - Parietal wall of the aperture
3 - aperture
4 - columella
5 - suture
6 - whorl
7 - apex
Here is a cute video of a hermit crab changing shells.
And an informative one
***Fun Fact
Coconut crabs are the largest living arthropod in the world. They can climb trees and open coconuts to eat the meat,however they are not a large part of the crabs diet.
Relate to Evolution
- uses a snail shell so never had to grow its own. (Like humans wear clothes so we prevent natural adaptations to protect us)
- the sea anemone helps the crab to camouflage along with containing poison to scare away predators.
- some eat their shells after molting out of them for nutrition.
- not fussy eaters which helps with survival. (eat decaying matter, random washed up plants, etc.
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