Optimizing metal bioaccumulation studies with Enchytraeus crypticus


Enchytraeids are important in soil formation processes and play a crucial role in physical, chemical, and biological processes in the soil. Enchytraeus crypticus has been proven to be an excellent model species for ecotoxicological tests, as it has a short generation time, good control performance and wide tolerance to distinct soil properties. Dermal and intestinal absorption are the major routes for the uptake of metals from soil in E. crypticus. The enchytraeids do ingest considerable amounts of soil. Similar to earthworms, gut load, therefore, may overestimate the internal metal concentration in the enchytraeids. Thus, gut clearance is necessary for a proper measurement of bioaccumulation in E. crypticus. However, no methodology was available in the literature for the gut clearance of E. crypticus. We therefore recently developed a method in which the enchytraeids are kept in an aqueous solution, but this approach needs optimization and further testing before it can routinely be applied.


An experiment will be performed with different metals (Zn, Pb, Cu, Cr) in a standard test soil following the enchytraeid reproduction test described by OECD guideline 220. Surviving animals will be removed from exposure containers and placed in an aqueous solution according to ISO guideline 6341 for gut clearance, using 7 time intervals (0 h, 3 h, 6 h, 12 h, 24 h, 36 h, 48 h). At each time point, worms will be collected for metal analysis. Internal metal concentrations in the animals will be measured by Graphite Furnace Atomic Absorption Spectrometry (AAS), after digestion in a mixture of ultrapure concentrated HNO3 and HClO4.

What you can learn

You will be taught how to identify useful literature, and you will gain experience with methods for culturing and toxicity testing of soil organisms, the design of (complex) experiments, experimental instruments for measuring metal concentrations in biological tissues (e.g., Atomic Absorption Spectrometry, AAS), modelling and statistical analysis of ecotoxicity data, etc. You will write a scientific report at the end of this internship, with the possibility of contributing to a publication in a peer-reviewed scientific journal.


Lulu Zhang T: +31 20 59 87085 E: l3.zhang@vu.nl and
Dr. ir. C.A.M. van Gestel E: kees.van.gestel@vu.nl

 Ecotox 2016-10