Detecting fungal spores and other palynomorphs in amber and copal by solvent treatment

Abstract

Organisms fossilised in amber include insects, plant remains and (rarely) fungi. One reason for the latter could be that fungal tissue decomposes quickly under the (sub-)tropical conditions where amber-producing trees thrive. Moreover, resin production is highest during drier seasons, while fungi usually occur during wetter periods. One way to improve the knowledge about fungal and similar records in amber may lie in looking for spores which are generally hardier than hyphal tissue. Traditional imaging methods mostly need laborious preparations, such as producing thin sections, without knowing whether microfossils are present in a sample. Here, a novel method to isolate fungal spores and other palynomorphs from amber using solvents is presented. Microscope slides can easily be coated with the suspended particles, embedded and microscopically examined. In this way, fungal remains including fungal spores were recovered from seven out of nine amber samples processed. A total of over 200 palynomorphs of various origins were extracted. They include pollen, moss and fern spores, and various cysts. At the same time, it became clear that treatment with nine different polar and non-polar solvents revealed provenance-specific solubility patterns. This simple ‘solvent fingerprinting’ may help identify provenances. Of all the provenances, Sumatran amber was the richest in all kinds of palynomorphs, and thus suitable to further develop the method, particularly concerning improved imaging. Mixtures of solvents should be tested that could enhance the particle yield of provenances with low solubility.