Meeting Abstract
Agonid poachers are benthic, heavily armored fishes with modified, robust dorsal scales that protect against predation from above. We hypothesized the mechanical properties of blacktip poacher, Xeneretmus latifrons, dorsal scales are more mechanically reinforced compared to lateral and ventral scales. Blacktip poachers (n=28) were separated into two treatments: intact and partially descaled fish. Puncture tests were performed using an Instron 5942 on 1) scaled fish, 2) partially descaled fish, and 3) the scales that were removed. We measured three mechanical properties for each treatment group: fracture point (strength), Young’s modulus (stiffness), and work of fracture (toughness). We calculated a mean ± S.D. for each treatment and compared the groups via ANOVA with post-hoc Tukey tests. Individual scales were 29% stronger than intact fish and 779% stronger than skin. Scales were 27% and 524% stiffer than scaled fish and skin, respectively, and 26% tougher than skin. Scales differed in strength, stiffness, and toughness between the dorsal, lateral, and ventral surfaces of the fish. Dorsal scales were significantly stronger (9.1MPa ± 5.6) than both lateral (4.8MPa ± 3.9; p=0.005) and ventral scales (5.7MPa ± 6.9; p=0.019). Isolated dorsal scales were significantly stiffer (10.4MPa ± 8.8) than lateral (5.9MPa ± 4.9; p=0.011) and ventral scales (5.3MPa ± 3.8; p=0.0009). Blacktip poacher scales are 1.5 times stiffer than bovid horn (keratin), and more than 5 times tougher than tooth enamel. Poacher scales are strong, stiff, and tough biological features that may provide biomimetic inspiration for future synthetic materials, such as puncture-resistant body armor.
