In article <6k19sa$mvc at newsstand.cit.cornell.edu>, aq12 at cornell.edu
> I am using earthworms (E. foetida) to examine availability and
> toxicity of soils with various oil fractions. In preliminary 7-day
> assays I have not found mortality even at rather high concentrations.
> However, I have seen what appear to be some dark markings (spots
> or pores) on the clitella of some worms. The apperance of these
> spots was not dose-dependent. If someone has similar observations
> I'd appreciate some coments on what this could be.
>> My preliminary assay was to check mortality alone but a more
> refined endpoint may be appropriate. Does anyone have
> suggestions? I am considering weight changes or burrowing time
> into a clean soil.
I have no idea of the equipment you have available but should you
have a fluorometer about you may want to consider monitoring
the induction of cytochromes P450, and more selectively the CYP1A
subfamily. You can do this with either benzpyrene hydroxylase
("AHH") or ethylresorufin-o-deethylase (EROD) activities. If you
have access to molbio facilities you could look for CYP1A1 mRNA.
Having said this I am not sure if this has been tried in
earthworms. These activities have been assayed in fish to monitor
pesticide exposure and I assume that the oil fractions will contain
hydrocarbons capable of inducing the enzymes in the worms.
Ah, I've just realised I'm showing my P450 bias in this reply
and may have misinterpreted your question. There is no causal
relationship (AFAIK) between CYP1A induction and toxicity so this
would be more of a biomarker for *potential* toxin exposure rather
than a genuine indicator of worm toxicity. Maybe this would be
suitable for your purposes...?
I hope that this helps in some way,
Bernard Murray, PhD
Dept. Cell. Mol. Pharmacol., UCSF, San Francisco, USA