Interactions that occur between members of different species that are beneficial to all involved are called mutualistic interactions. Cleaner shrimp are an example of a species involved in these interactions. These shrimp live at underwater cleaning stations and interact with client fish. The cleaner shrimp eat parasites and dead skin from the client fish and in turn receive a meal. This cleaning interaction can be risky for the shrimp as some clients are predators. Therefore, the shrimp must assess the risk of cleaning the client and change their behaviour if necessary. This is how they identify themselves as cleaners and not prey.
This study analysed video footage of cleaner shrimp and client fish. This was to observe whether shrimp change their behaviour based on if they were interacting with a predatory or non-predatory client. Laboratory experiments were also done to investigate other factors that may affect the behaviour of the shrimp. It was found that predatory clients were cleaned significantly less often than non-predatory clients. The shrimp were observed rocking their legs around predatory clients but not around non-predatory clients. They also displayed this leg rocking behaviour more often when the client fish were larger and when the environment was dark. It was suggested that jolting from fish indicated that the cleaner shrimp had cheated, meaning eaten healthy flesh from the fish. There was not a statistically significant difference in how often they cheated predatory vs non-predatory clients.
It was concluded that cleaning occurred less often when the risk of being eaten was higher, such as in darkness or when clients were larger. This led to a significantly higher amount of 2 non-predatory clients being cleaned. The amount of times a fish jolted did not depend on if they were a predator or not. However, it is not known if jolting truly indicates cheating from cleaner shrimp. It was also suggested that the cleaner shrimp use the leg rocking behaviour to indicate that they are cleaners and not prey. Signals may be important for mutualisms to happen in the first place and to continue over time. This is because they allow individuals to know when and how to interact with mutualistic partners. There is evidence of behavioural adjustments in some shrimp species but not all. This suggests that these cleaning behaviours have evolved independently in different species. Author of entry: Nia Parry-Howells