Effectiveness of five different solutions for preserving aquatic insects commonly used in morphological and stream ecology studies

Sample fixation and preservation are crucial steps for biological research. This is especially true for resolving ecological changes across various spatial and temporal scales based on sediment and/or macrozoobenthos samples, recognized to be efficient indicators of habitat quality and ecosystem health in aquatic environments. Thus, it is very important to find a convenient method for long-term sample storage. In this study, we compared effectiveness of five different solutions (glyoxal, 3.6% formaldehyde, NBF, 70% ethanol, 99% ethanol) for the preservation of macroinvertebrate taxa commonly found in stream habitats (i.e. families of aquatic insects, Chironomidae, Baetidae, Ephemeridae, Heptageniidae), with the aim to find a new “gold standard” fixative that could replace formalin, recognized to have significantly adverse health effects if exposed to it. To estimate the effectiveness of these solutions on all macrozoobenthos samples/taxa, color contrast and tissue preservation within hematoxylin and eosin stained slides were assessed as well as the preservation of body parts and tissues of collected specimens. Our results show that different preservatives/fixatives yield different effects on the tissue preservation of different organisms. None of the tested preservation liquids prove to be unique formalin successor that could serve as a new “gold standard” for preserving macroinvertebrate taxa commonly found in morphological and stream ecology studies. The efficiency of different solutions in preserving macroinvertebrate tissue integrity depends on the chemical properties and concentrations of the solutions for sample storage, tissue type as well as on the dimensions and structure (e.g., the extent of chitin coverage) of the studied organisms.