Shawn Miller /Science of the Whole Environment
An artificial shell is now fashionable for hermit crabs
ENVIRONMENT – Hermit crabs are known for their magnificent shells, which they adopted from other species. But according to a study published Jan. 25 in Science of the Total Environment, these crustaceans now have a new hiding place: the plastic bits that litter the ocean floor.
According to an estimate by the European Commission, between 5 and 13 million tonnes of plastic end up in the oceans every year. With increasing marine pollution, these animals had to cope.
In photos shared on social networks and special underwater photography sites, scientists discovered 386 specimens showing this new habit. Ten of 16 species of terrestrial hermit crabs are beginning to replace their shells with plastic parts, particularly bottle caps.
From the shell to the plastic
Unlike other crustaceans, hermit crabs have a soft belly that is vulnerable to the sun and other animals. To protect themselves, they then hide this body part in a shell that they stole from another animal and which they change as their body grows.
Science of the entire environment
The hermit crab selects debris to build a brand new shell
Given the decline in the number of molluscs and therefore the number of shells available, hermit crabs have found an equally valid and beneficial option: a shelter made of plastic, which is easier to find given the amount of waste in our seas. According to experts, plastic items are also more convenient and easier to transport. This proves to be a very effective strategy for escaping predators: hermit crabs can quickly hide in their artificial shells and camouflage themselves among the debris on the seabed.
Corks, a seduction technique
The cover doesn't just have the function of a shelter. Men actually use this outfit to strut in front of women. When mating, they use this criterion to select their mate based on size and other factors that indicate the male's fertility. Dressing with a clearly visible and larger plastic cap could then be a completely new seduction technique developed by men.
Science of the entire environment
The hermit crab selects debris to build a brand new shell
This adaptability that we are increasingly observing in animals is not only positive. When a hermit crab dies, it sends out olfactory signals to indicate that it is leaving its shell for others to use. However, plastic materials in the sea emit the same chemical that easily attracts crustaceans. But what awaits them is often a tragic end. According to a study published in 2020, 570,000 crabs die each year stuck in debris on tropical islands looking for a new home.
Scientists are also concerned about the impact these new practices could have on the evolution of the hermit crab species. Although they have adapted to the new environment, plastic materials have a direct impact on the animal's reproduction. We will then have to wait for further studies to estimate the extent of the consequences.
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