Cyst-based toxicity tests. VI: Toxkits and Fluotox tests as cost-effective tools for routine toxicity screening

During the last two decades microbiotests have been developed which are independent of recruitment, maintenance and/or culturing of live stocks of test organisms. "Culture and maintenance free" microbiotests have been worked out in the Laboratory for Biological Research in Aquatic Pollution at the University of Ghent, with selected aquatic invertebrates. The new approach is based on the use of "resting stages" (cysts) as inert biological material from which live test organisms can be hatched "on demand". The "cyst-based" bioassays have recently been miniaturized in Toxkits. Four cyst-based screening tests have reached the stage of commercialization: two freshwater 24h-LC50 tests (Rotoxkit F and Streptoxkit F) and two estuarine/marine 24h-LC50 bioassays (Rotoxkit M and Artoxkit M), based on cysts of rotifer and crustacean species, respectively. Recently, the same laboratory has also been focusing on the development of a "rapid" (one hour) sublethal bioassays with aquatic invertebrates. The so called "Fluotox" screening test is based on the visual observation of in vivo inhibition of an enzymatic process, using a fluorescent substrate. Besides the advantages of rapidity and cost-effectiveness, the Fluotox assay also appears to have a remarkable predictive potential for mortality, as displayed by the remarkable correlation between the Fluotox 1h-EC50's and conventional 24h-LC50's with the same species.