Invertebrates
Click on the thumbnails below to enlarge images.
Web of Tetranychus urticae (spider mite)
Image courtesy of technical staff at the Servicio de Instrumentación Tecnológica (SAINT) - a central multi-disciplinary EM facility at the Universidad Politécnica de Cartagena, Spain.
Critical point dried aphid
There are more than 300 species of aphid within the UK, feeding on a variety of plants. Identification can be difficult and highly dependent upon subtle taxonomic structural features.
SEM is an ideal technique for the isolation of these features, but the aphids themselves present problems in preparation for the technique. Unlike many insects that can be readily prepared for SEM by air-drying with artefact, aphids are highly hydrated and susceptible to shrinkage and distortion.
Even critical point dried specimens undergo considerable gross structural changes. As shown in these images, the abdomen shrinks and collapses, and most of the thin ribbons of wax, which are present on many aphid species, are entirely dissolved away by acetone dehydration.
Low-temperature SEM is therefore a preferred method of preparing these very delicate organisms - see frozen hydrated aphid for comparison.
Frozen hydrated aphid
In comparison with the critical point dried aphid, this image shows that there is no distortion of the abdomen nor any other parts of the aphid following freeze drying. The delicate patterns on the surface of the abdomen (probably chitin or wax, and an important taxonomic feature) are well preserved.
Fungal infection of aphid
Scale: width of spore head = 15 microns.
Image courtesy of Klaus Qvortrup at The Panum Institute, University of Copenhagen, Denmark.