300 Hermit Crabs Use Plastic As Shelters Instead of Natural Shells

(Photo: Wikimedia Commons/H. Zell)
300 Hermit Crabs Use Plastic as Shelters Instead of Natural Shells

Land hermit crabs have been observed using bottle tops and plastic items as their shelter. A good enough shell is key to survival, so how hermit crabs choose their shell is important.

Hermit Crabs Shell Selection

Hermit crabs are a great model organism to study because of how easily the changes in their behavior can be detected. They use the empty shells left by dead snails to protect their bodies, rather than constantly building their shell as a lobster or regular crab would. The shell shields its soft abdomen while it moves around, but if it feels threatened, it retreats completely within the shell. Their shells can be used as makeshift shelters.

Individuals must have a sufficient shell to survive, s, they gather and improve their shel as they maturels. They compete with other hermit crabs for available shells and determine the appropriateness of newly discovered shells.

Their main concern is finding large enough shells to cover them, but they also consider the type of snail shell, its condition, and even its color, which might affect how noticeable the crab is.

The actual availability of appropriate shells is another aspect that limits the choice of shell. A recent study discovered that some land hermit crabs favor plastic objects over their native shells for an unexplained reason.

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Why Do Hermit Crabs Choose Plastic Items For Shells?

Polish researchers had numerous questions that they wanted to answer. First, to what extent is plastic garbage replacing shells in the environment?

The study found that 326 crabs were seen utilizing plastic as shells. Even if the number seems high, it's probably an underestimate of the actual number because users will probably only see crabs in areas of the population that are easily accessible.

On the other hand, it appears likely that users may upload more visually arresting or unique photos. Therefore, the iEcology method may overstate the percentage of people in a group who prefer plastic to real shells. So, organized field surveys are required.

Secondly, are certain crabs using plastic? One explanation is that there may not be enough natural shells for them. However, further data on the demographics of the local snail populations would be necessary to test this theory.

The researchers also wonder if the crabs find plastic more appealing or easier to detect than actual shells. Plastic may be lighter than identical shells, as the authors point out, providing the same level of protection but requiring less energy to carry. Fascinatingly, compounds that seep out of plastic have been observed to draw sea hermit crabs by emulating the smell of food.

This raises a third query regarding potential drawbacks to plastic use. Plastic debris tends to be brighter and may contrast more with the background than real shells, which makes the crabs more susceptible to predators.

They also know that hermit crabs' behavior can be altered by exposure to microplastics and compounds derived from plastic. This can result in the crabs becoming less picky about the shells they choose, less skilled in shell fights, and even a change in personality as they become more willing to take chances.

The researchers should conduct several lab tests to understand the hermit crabs' shell-choosing behavior better and address the reasons for and effects of their use of plastic garbage.