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The Gap Year Blog

Everyone Loves Hermit Crabs - Into The Wild Blog - Frontier

10 May 2018 14:05 PM

Actually maybe it’s just me that loves hermit crabs, but how could you not?! They’re one of the funniest, coolest things hanging around on the bottom of the ocean.

We see lots on our mangrove surveys here in particular. And it probably shouldn’t be, but it is quite funny to see how many of them drop off of the mangrove root or other stem they’ve been clinging on to as you snorkel over them. It’s an easy way to tell if the shell belongs to a snail or a hermit crab – a hermit crab will move as you approach.

However, despite this and their name, they’re very social creatures. I particularly love the fact that they won’t go around another hermit crab, nope, they climb straight over the top! But I never knew that much about them, so here are a few interesting facts I found out:

1. Hermit crabs are usually nocturnal

2. They use gills to breathe

3. They have 10 legs! Like other crabs the left claw is usually larger, to use as defence against predators

4. Like other crabs, in order to grow they moult their old exoskeleton as a new one grows underneath. Younger ones do this every few months, but once they reach adulthood it becomes only every year or so. 

5. However hermit crabs also have to think about upgrading their shell as well. They tend to use the abandoned shells of gastropods to live in to protect their vulnerable abdomen, but can exchange with each other, and often compete for the best shells. 

6. They’re pretty social with other species. I saw one hermit crab in a shell with a bivalve also living on that shell – now that’s what I call a double whammy! And sometimes they pair up with anemones, which can sting potential predators for the hermit crab, and the anemone gets the crab’s leftovers and a free ride. What a great example of a commonly beneficial symbiotic relationship. So maybe everyone does love hermit crabs! 

By Joanna Read - Research Officer | Tanzania Marine Conservation

Frontier runs terrestrial & marine conservation, community, teaching and adventure projects in over 50 countries - join us and explore the world!