Using relative brain mass to better understand trophic interactions and phenotypic plasticity of invasive lionfish (Pterois volitans)

Understanding predator-prey relationships gives greater insight into coral reef health. A recent study on predator-prey relationships linked the relative brain mass of predators and their prey. Predation pressure forces prey to use decision making skills that require higher cognition by inspecting and identifying predators and then adjusting their behavior to achieve the highest chance for survival. However, the predation pressure that prey face outweighs the pressure predators face to find a prey. This results in prey having larger relative brain masses than their predators. There is little data on relative brain mass of fishes with few natural predators such as Pterois volitans. This study compared the brain mass to body mass ratio of P. volitans, which have very few natural predators and thus very little predation pressure, to the brain mass to body mass ratio of their prey, possible predators, competitors, and taxonomically similar fish. This study also analyzed the response of lionfish to divers with nets in order to investigate their ability to recognize divers as predators. Lionfish did swim away from divers 56.5% of the time which indicates that lionfish might be able to recognize divers as predators. Lionfish had a significantly smaller relative brain mass than their predators, prey, and competitors, but was not significantly smaller than taxonomically similar fish. These results demonstrate that the morphological antipredator adaptation of venomous spines cause very little predation pressure. Thus, lionfish are not forced to use the same cognitive skills as other prey or predators and in turn have smaller relative brain masses.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 10-20 from CIEE Bonaire.

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