Elemental composition of Daphnia Daphnia are planktonic crustaceans and members of the order Cladocera. Because of their small size of 0.2 to 5 mm and their jumpy swimming style, Daphnia are commonly known as water fleas. Their aquatic living environment can range from rivers, streams, lakes and ponds to acidic swamps. Their short lifespan, their reproductive capabilities and especially their sensitivity to contaminants make them an indicator species in the field of environmental toxicology.Daphnia are for instance used to test the effects of toxins on ecosystems. Because Daphnia are almost transparent,their internal organs are easy to examine in live specimens. The performed examination demonstrates the capabilities of -XRF as a method for the analysis of these biological species regarding elemental composition and the possibility to use it also for environmental control. The samples A single Daphnia is shown in figure 1. The size of the water flea is less than 3 mm. The photo shows the thin, partly transparent body and the head with a large eye. The body is protected by a thin and transparent carapace. The most prominent features are the eyes, the second antennae and a pair of abdominal setae. Measurements were performed on two samples. One of them was fed with nano-particles which were tagged with Au(sample 2). The samples were prepared on a quartz support that gives a relatively high spectral background due to scattering and a Si fluorescence signal. 微區(qū)X射線熒光光譜儀 生命科學(xué)