A Novel, Efficient Method for Otolith Specimen Preparation Using UV‐Cured Resins

Abstract

Otoliths are calcified structures that are located in the inner ears of fish, as in most vertebrates, that are responsible primarily for the perception of gravity, balance, and movement and secondarily of sound detection. Microstructural and chemical analyses of the inner otolith growth layers, called increments, constitute powerful tools for estimating fish age and elucidate many life history and demographic traits of fish populations. Otolith analyses often require the production of a thin cross section that includes the otolith core and all increments formed from birth (core) until the moment of collection (otolith edge) in the same plane of view. Here we report on the suitability of single-component UV-cured resins to obtain otolith cross sections for both microstructural examination and chemical analysis by electron probe microanalysis. Embedding blocks that were produced with UV-cured resins had transparency that was comparable to that of the commonly used two-component epoxy resins and provided similar adhesion and mechanical support for the otoliths during grinding or cutting with a precision cutter and analysis. In addition, UV-cured resins offer on-demand, extremely rapid (minute-order) hardening that makes them useful in classroom situations in which time for otolith embedding becomes a constraint.

Where the Ends Meet: An Overview of Sex Determination in Atheriniform Fishes

“…Otoliths are calcified structures located in the inner ears of fish that are responsible primarily for the perception of gravity, balance, and movement. They grow by accretion of layers (increments) starting from a nucleus present at birth, and the chemical composition of each layer is affected by the physicochemical characteristics of the surrounding environment, making it possible to determine the birth date (hence the age) and even reconstruct the environmental history of individual fish [Strüssmann et al, 2020]. The combination of molecular and otolith-based tools dramatically increases the analytical resolution to tackle environmental influences on sex determination compared to what can be obtained solely from the analysis of phenotypic sex ratios.…”