How can Microplastics make Crabs less Smelly?!
Mae Dorricott
Scuttling across the rocks that lie between two worlds controlled by the tides the common shore crab, (Carcinus maenas), searches for his nutritious snack. With claws poised, he is ready to crack open his prey, the common periwinkle (Littorina littorea).
Hiding amongst the seaweeds the fleshy foot of the periwinkle glues itself to the rocks. Protected within its spiral shell this snail’s self-made home is built to evade the crush of the crab’s claws. Obviously too slow to run away, the periwinkle depends on his ability to sniff the crab coming. Using chemosensory, the ability to detect chemical changes, the periwinkle is able to sense the crab as he approaches and retreats within the safety of his shell… usually.
But little does the periwinkle know, his defence has been compromised.
Littorina littorea, the periwinkle, retreating within the safety of his shell. Image Available here:
Research from the Centre National de la Recherche Scientifique (CNRS) in France, reveals that periwinkles exposed to microplastics can no longer “smell” the crab coming.
Plastic is a porous material, allowing it to collect chemicals from the marine environments as it drifts through the environment. These toxins can also leach out into the surrounding water and potentially impact organisms in the area.
Fragments of plastic found in the sea. Microplastics are classed as plastics that are smaller than 5mm. Photo: Mae Dorricott @maekld
During this study, the CNRS placed Periwinkles in water with a concentration of microplastic pellets. “New” plastic pellets were compared against plastic pellets that had been collected from the environment.
Where new pellets had little effect on the periwinkles behaviour, the pellets that had been collected from the sea had a significant impact on the snails.
When exposed to microplastics collected from the ocean, the periwinkle’s ability to smell the crab was weakened. Usually, the snail would retreat into its shell when it senses a nearby crab’s pheromones, but with plastic pellets in the water, the periwinkle wasn’t able to smell the crab pheromones introduced into its tank and didn’t withdraw into the safety of its shell.
Carcinus maenas scrambling through intertidal weeds. Photo available here.
So, what does this experiment mean for the periwinkle?
We’re all very aware of the presence of plastics in the ocean and that many animals accidentally ingest them. There may be further consequences we have yet to consider, yet this is the first piece of evidence that suggests plastics can even affect the way organisms interact with each other, like predator and prey interactions. While this experiment was done in a laboratory microplastics are likely causing these same problems in your local tidal pool.
Plastic Not Fantastic, part of our Research Series, highlights recent research efforts into the effects of plastic on marine life, and showcases organisations, individuals and initiatives fighting against the plastic tide
IF YOU'VE ENJOYED READING THIS ARTICLE, LOOK OUT FOR MORE PLASTIC NOT FANTASTIC blogs from MAE AND FOLLOW HER HERE @MAEKLD
References
Seuront, L. (2018) Microplastic Leachates impair behavioural vigilance and predator avoidance in a temperate intertidal gastropod. Biology Letters. 14 : 20180453