Otoliths, bones, teeth, and more: Development of a new polishing wheel for calcified structures

Abstract

Biochronological information stored in the calcified structures of organisms provide fundamental organismal, environmental, and ecological data. Bones, teeth, statoliths, corals, and otoliths are widely used to answer a myriad of questions related to trophic position, migration, age and growth, environmental variation, and historical climate. Many calcified structures, particularly the ear stones of fishes (otoliths), are small (50 μm to 5 mm) and require precise preparation methods, which vary depending on the structure and research question but commonly include embedding, sectioning, and polishing prior to structural or chemical analysis. Globally, management agencies rely on the precise polishing of millions of otoliths each year to obtain vital demographic data, such as age and growth. However, this process is time consuming, labor intensive, and ergonomically strenuous. Since the early 1970s, there has been limited advancement in preparation methods with many still using manual approaches or costly, and at times inefficient, equipment. Therefore, we designed and fabricated an affordable, adjustable speed, multi-wheel polisher, which can be powered with alternating or direct current. Sample preparation time is reduced, and sample consistency is notably improved compared to manual approaches. While specifically designed for consistent and relatively rapid preparation of otolith thin sections, the polisher is readily adaptable to a variety of applications. Designs and manufacturing for these wheels are publicly available through the iLab at Oregon State University.