Hermit crab

Hermit crabs “attracted” by certain plastic toxins in oceans

Hermit crabs may be “excited” by an additive released by plastics in the ocean, according to research from a team at the University of Hull.

Oleamide is a plastic additive which is already known to be a sex pheromone – or “stimulant” – for certain species of marine life, such as shrimps.

The research team at the University of Hull, including PhD candidate Paula Schirrmacher, has now been studying the combined impact of climate change, plastic and other molecules in the ocean on hermit crabs.

A study has found that once detected, oleamide was found to increase the respiration rate of hermit crabs – indicating excitement and attraction.

Oleamide can also be mistaken for food by scavengers, meaning hermit crabs may travel a distance in search of a meal, only to discover plastic instead.

Ms Schirrmacher said: “Our study shows that oleamide attracts hermit crabs. Respiration rate increases significantly in response to low concentrations of oleamide, and hermit crabs show a behavioural attraction comparable to their response to a feeding stimulant.

“Oleamide also has a striking resemblance to oleic acid, a chemical released by arthropods during decomposition. As scavengers, hermit crabs may misidentify oleamide as a food source, creating a trap.

“This research demonstrates that additive leaching may play a significant role in the attraction of marine life to plastic.”

The MolStressH2O research cluster, led by Dr. Katharina Wollenberg Valero, examines the combined impact of climate change and plastics on ocean life.

The research cluster has recently published three studies which reveal marine invertebrates along the Yorkshire coast are being negatively affected by global climate change.

The second study found that plastic pollution in the oceans, coupled with ocean acidification, can affect male and female mussels differently.

PhD student Luana Fiorella Mincarelli, also working in the cluster, said: “It is critically important to understand how plastic additives work on molecular levels, especially on reproductive success.

“We have found that their toxic effect can be amplified in a climate change scenario.”

Her research shows that male blue mussels were mostly affected by increased temperature, but females were more sensitive to DEHP – a toxic chemical found in many plastics.

The research concluded that rising sea temperatures, combined with increased plastic pollution, can confuse their breeding cycles and therefore impact on reproduction rates.

Another strand of research examined how hermit crabs smell in acidified oceans.

Previous studies have suggested ocean acidification impairs the sense of smell of marine animals – in turn, limiting their ability to communicate.

Dr Jorg Hardege, Reader in Chemical Ecology at the University of Hull, said: “Whether or not marine animals can smell plastics is a topic that previously attracted a lot of scientific controversy, but there was not much actual data.”

However, research conducted by Ms Schirrmacher on hermit crabs found in Robin Hood’s Bay has now found that the creatures were actually attracted to a chemical cue known as PEA (2-phenylethylamine).

PEA is known to warn mammals and sea creatures of predators, and its effectiveness may be increased in an acidified ocean.

Dr Christina Roggatz, a researcher at Hull whose work features molecule structure changes under ocean acidification, said: “To receive smell-related information correctly, the odour molecule needs to properly fit and bind to the receptor.

“Our results show how lower environmental pH causes small changes in the chemical properties of the odour molecules, which in turn facilitate this crucial binding step.

“In short: pH can make or break successful communication in the ocean.”

Find out more about research in the Department of Biological and Marine Sciences.

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