- Having no natural protection of their own, hermit crabs normally used discarded mollusk shells as shelter.
- However, the iEcology study shows that the mollusk shells that hermit crabs choose as shelter are replaced by plastic waste.
- The most likely reason why hermit crabs use plastic waste as shelter is the increasing environmental pollution and the fact that the material that provides the best camouflage among the garbage on the shore is also the garbage on the shore.
Terrestrial hermit crabs survive as soft-bodied crustaceans that live near water in tropical regions of the world. Having no natural protection of their own, these crabs normally use discarded mollusk shells as shelter. However, this solitary terrestrial crab species has begun to prefer plastic objects found in beach garbage as shelters.
A new study by a team working at the Center for Biological and Chemical Research at the University of Warsaw and the Department of Zoology at Poznan University of Life Sciences, Poland. Science of the Total Environment It was published in the magazine.
Increasing plastic pollution currently accounts for 85% of marine pollution worldwide. Current research shows that most of the plastic pollution in the Earth’s oceans is transported through rivers, leading to the accumulation of plastic waste on shorelines. Terrestrial hermit crabs live on all tropical coastlines around the world and typically use the empty shells of gastropods to protect their soft abdominal areas, known as pleons.
Studies on crab shell selection show that the main factors include the chemical signals collected from the shells, the proximity of predators, the quality of the shells, and the growth rate of the individual crab. Shells are also shown to play a role in sexual signaling, as the size and condition of male crabs’ shells influence females’ mate choices.
In this new research, the team adopted an internet ecology (iEcology) approach, which involves examining digital content (audio recordings, videos, images, news, and user activity posts) published on news sites, social media, and other platforms to learn about aspects and processes of ecological phenomena. “Although the validity of data collected on social media platforms has been easily proven in the field of conservation, its application to ecology and evolution is still very limited,” the researchers wrote about iEcology. says.
To measure the hermit crabs’ behavior, the researchers examined images posted on various online platforms and matched their findings with a literature review. The study article notes that the literature review alone has yielded four publications to date reporting on a total of 10 creatures, including two terrestrial hermit crab species, three marine hermit crab species, and five artificial crustaceans.
Researchers identified 386 individual crabs with artificial shells from 10 of 16 total terrestrial hermit crab species. In the majority of images collected, crabs were seen using black and white plastic caps (84.5%; 326 of 386 images). Crabs with only metal or only glass shells represented 5.4% each, while the remaining 4.7% had both metal and glass shells.
Possible misleading factors regarding images should also be taken into account: Plastic is often more easily noticed by humans due to its contrasting color than other anthropogenic or natural materials, thus affecting the frequency of reporting. Additionally, data collected through iEcology may be affected by potential bias among observers resulting from a variety of factors affecting data collection. These factors include individual and cultural subjectivities, such as the likelihood of sharing unusual behavior online.
Why plastic instead of natural shells?
Discussing possible reasons for this behavior, the team points out the environmental availability of plastic waste as well as the decline of gastropod shells due to local human activities. Researchers also suggest factors play a role in individual choice. These factors can be listed as follows: the attractiveness of artificial materials to mating females, lighter weights of artificial shells that can benefit the hermit crabs’ energy, the scent cue emitted by dimethyl sulphide, which is found in both natural shells and marine debris, and
Considering that the choice of shell is often made to adapt to the local environment, the possibility that artificial shells may serve more effectively as camouflage in polluted areas. Of course, all of these are issues that need further research.
The researchers asked, “Are artificial shells paving the way for a new evolutionary trajectory in hermit crabs, or are they an ecological and evolutionary trap of the Anthropocene?” he asks. Although this new behavior is considered a clever adaptation, the main factor behind it is undeniable. In this context, what this habit ultimately means for the evolution of terrestrial hermit crabs remains to be investigated.
Compiled by: Fatma Ebrar Tuncel