Meeting Abstract
Armor, in the sense of heavy plates or scutes, has evolved many times in fishes suggesting a common selective pressure or many different selective pressures. In the engineering world armor can defend against impact, abrasion, cutting, and/or crushing. In the realm of biology we must add display, offensive battery, and ritualized combat to the functions of armor. Here we explore the notion that looking at the damage pattern on armor over ontogeny can reveal something of function. For example, armor that is unscathed from birth to death likely serves only as display, else it would bear the marks of use. We used the Northern Spearnose Poacher (Agonopsis vulsa), a heavily armored benthic fish, belonging to the family Agonidae. A. vulsa’s bony scales preserve damage incurred during the fish’s life. Using CT scans and digital 3D modeling, a categorical systemization of damage was created, assigning values to specific degrees of macroscopic damage. These degrees of damage were investigated before data collection through observation of many scales, both damaged and undamaged. To ground truth damage modes scales were intentionally damaged (shattered, abraded, snapped, and crushed) and observed using SEM. Categories of damage were designated as caused by impact (mild or severe breakage) or caused by abrasion (mild or severe wear). This systemization was applied to 34 A. vulsa specimens ranging in trunk length from 2.3 cm to 14.2 cm. Large fish (over 9 cm) and small fish (under 9 cm) showed different patterns of impact damage locations along the fish. Large fish also showed significantly more abrasion damage. These patterns of damage may provide new insights into the life history of this small, largely unstudied fish.
