Neuroanatomy and Behavior in Invasive Hearing Specialist Fishes
Open AccessInvasive animal species have widespread impacts on naive ecosystems, such as displacement of native fauna and increased competition for limited resources. Anthropogenic activities have resulted in the frequent introduction of nonnative species in many ecosystems, but very few introduced species become invasive, revealing that there are a set of characteristics beneficial for invading new ecosystems. These characteristics can be behavioral or morphological in origin and are often shared between species invading similar ecosystems. One example of this is the shared behavioral and morphological traits in invasive cypriniform fishes. Cypriniformes are a large order of freshwater fishes characterized by a suite of evolutionary morphological novelties, such as highly modified trophic apparatuses and hearing structures, as well as behavioral novelties such as robust collective social behaviors and widespread gregariousness. The relationship between large scale behavioral traits and variability has been well studied in invasive fish species, but less so in invasive Asian carp and their immediate relatives. Using goldfish, we investigated how behavioral phenotype is related to invasiveness in novel environments. We found that higher behavioral variability within a species is not directly related to the invasiveness of that species. In addition, there were no single behavioral traits measured that directly related to a higher increase in invasion success at the species level. Instead, robustly correlated behavioral traits that work together at the species level reveal differences that may be related to the potential for invasion success. A component of invasion biology that is just beginning to be investigated in fishes is how differences in sensory perception relate to organismal, and therefore, species success in a novel ecosystem. We explored how sensory limitation, reflecting a human-altered environment, impacted critical social behaviors necessary for organismal survival. We found that a collective social behavior, shoaling, is possible with slight sensory limitation that still allows vision and hearing perception between social groups. Severe sensory limitation, resulting in hearing-only perception between social groups significantly altered shoaling in all species tested. This reveals that vision is a critical component of shoaling behavior, but hearing specialist fishes, like cypriniforms, are still able to rely on their morphological novelty to provide some information to help them perform collective social behaviors. In addition to behavior, brain structure is a strong indicator of organismal sensory perception. Neural ecomorphology, or how the environment relates to brain structure and function, reflects sensory capabilities, cognitive potential, and motor abilities. In fishes, the environment can play a strong role in the development and maintenance of brain regions and therefore, the more robust a region of the brain, the more likely the fish relies on the function that region provides. We found variation in regional volume between species and shape differences within those regions across three Asian carp species threatening the Great Lakes system in the United States. This suggests that there may be differences in how these organisms perceive and interact with their environments, establishing that the functional neural ecomorphology of these invasive fishes should be further investigated.
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