Four examples of scanning electron microscopic (SEM) images of parts of D. magna showing numerous bacteria attached to different surface structures. A. Head of D. magna. The white filamentous structures on the surface are bacteria. B and C. Surface of the carapace with bacteria attached. The thin lines on the carapace denote epidermis cell boundaries. D. Parts of the filter apparatus of D. magna. The oval objects are bacteria. None of the bacteria have yet been identified. Scale bar 200 μm in A and 10 μm in B, C and D.