Effect of Alcohol-Based Preservatives on Quality of Beetle Larval Specimens

Abstract

The standard procedure for fluid preservation of insects consists of two steps. First, the specimen is killed and prepared in a fixative fluid and then transferred to a storage fluid. Recommendations for using specific chemicals or mixtures differ depending on the size and anatomy of the animal and vary among the authors. However, controlled comparative studies are often missing. The ideal method should preserve the specimen�s morphology as well as its genetic information. We have investigated the effect of 12 combinations of commonly used methods based on ethanol, using four types of fixatives (Hot Water Kill (HWK) for 5 minutes/6 hours; absolute ethanol cold/boiling) and three types of storage fluids (70 %; 80 %; and absolute ethanol) after eight months of storage. The effects were tested on mature larvae of a forensically relevant beetle species. We have evaluated the effectivity in terms of color preservation, shape of the specimen, and quality of genetic material. The color was best preserved by HWK for 5 min with subsequent storage in absolute ethanol, and the worst results were achieved by cold absolute ethanol with subsequent storage in 70 % ethanol. The fixative type has a major effect on the shape compared to the storage fluid. The effect of treatments on shape appears to be inverse to the effect on color preservation. The genetic material was preserved equally well in all treatments. The advantages and disadvantages of specific treatments and the recommendation of the best method are discussed.