Differential effects of preservation on the estimation of biomass of two common mayfly species

Abstract

Despite the lack of definitive studies, researchers generally assume that preservatives do not alter the size of aquatic invertebrates, and thus seldom correct for any effect of preservation on the size of studied specimens. We determined the effects of preservation in ethanol (70%, 95%) and formaldehyde (5%, 10%) on the body length of the larvae of two common mayfly species, Baetis rhodani and Ephemerella ignita. Changes in body length varied depending on the species and preservative used but were not related to specimen size. Length of individuals of both species did not show any further change with increasing time of preservation. The estimation of biomass through length-mass regressions was biased up to 38% because of sample preservation. Preservation in 5% formaldehyde did not affect individual lengths of the 2 species and should be used in cases when measures are unfeasible on unpreserved animals.