About the Crustiness of Poachers

Abstract

Agonidae is a family containing 46 species of bottom dwelling fish. All of them possess heavy body armor, beneficial against predators and aggressive conspecifics. However, these types of useful traits usually come at a cost. We hypothesized that poachers pay for their armor in reduced maneuverability and increased body stiffness. In order to test our hypothesis, we investigated the natural flexibility of an Agonidae representative, Agonopsis vulsa, by analyzing videos of its flight response, and found that the fish are quite flexible. Additionally, we used a subset of sacrificed specimens in bending experiments to determine the body stiffness. The fish were bent in three different states (intact, with the plates removed, and with the muscle removed remaining only the vertebral column) to quantify the contributions of each layer to whole body stiffness. Finally, to quantify the protection gained from the armor, we looked at the material properties (stiffness) of the plates. We used material testing to determine the Young’s modulus of the plates and compared it to the one of vertebral bone from the same specimens. We found no difference in Young’s modulus between plates and bones. While the plates do contribute to stiffness in the fish, the extent to which they do was not as pronounced as expected. In addition, they contribute much more heavily to the stiffness of the body region than the tail region