Meeting Abstract
The family Agonidae comprises a variety of marine bottom-dwelling fishes whose scales have been modified into bony plates. Being part of body armor, these plates have to be hard and strong to exercise a protective function. However, to prevent agonids (who lack a swimbladder) to be stuck at the bottom under heavy armor, these plates better be low in weight. To investigate how agonids deal with this mechanical trade-off, armor plates of a common species of the Northeastern Pacific Ocean (Agonopsis vulsa) are examined microscopically. Using a combination of scanning electron microscopy and CT-scanning, a network of interconnecting bony trabeculae is observed in all investigated plates along the body. This network, being founded upon a solid surface of concentric bands of bone and supporting a solid posteriorly directed spine in every plate, creates cavities throughout the central mass of the plate, reducing it in weight. To examine the protective capacity of the plates, a finite element analysis is performed. This analysis shows not only that the observed composition of these plates is highly efficient in dealing with external forces, but also that trabeculae are oriented in such a way that potential failure points of the plates under external pressure are structurally reinforced. Additionally, scanning electron microscopy images of the plates of two closely related species (Bathyagonus alascana and Anoplagonus inermis) are made to find out whether closely related Agonidae species deal similarly with this trade-off. These images show that macroscopically similar plates do have microscopically different surfaces within this family of armored fishes.
