Extracting invertebrates from bryophytes

Many studies that are concerned with the ecology and conservation of invertebrate populations and communities use techniques to sample and extract invertebrates from their habitat. The effectiveness of different techniques to extract invertebrates from substrates has been the source of much debate amongst ecological entomologists. There is no single method which is 100% effective in extracting all invertebrates from substrates (Geurs et al., 1991; Walter et al., 1987). Determining the most appropriate method for a given study involves a compromise between cost and efficiency, the type of substrate sampled and the aims of the study (Edwards, 1991; McSorley and Walter, 1991; Walter et al., 1987). In addition, it is often impossible to extract live invertebrates from samples when working in remote locations, consequently methods are needed for preserved samples. Within these constraints several methods (e.g. sugar flotation, centrifugal flotation, heptane flotation) have been devised to extract invertebrates from substrate in preserved samples (Edwards, 1991; Geurs et al., 1991; McSorley and Walter, 1991; Upton, 1991; Kethley, 1990; Norton, 1990; van Gundy, 1982). When working with soft-bodied microinvertebrates, extraction techniques are required that are effective in extracting a high proportion of these taxa as well as maintaining the samples in an adequately preserved state. In view of all these limitations, it is essential when choosing an extraction technique for a given study that several techniques be trialed, preferably experimentally, however, it appears this is rarely done. Keeping these criteria in mind we devised an extraction technique, kerosene-phase separation, to extract invertebrates from preserved samples of bryophytes.