title: Limits of the fish embryo toxicity test with Danio rerio as an alternative to the acute fish toxicity test
creator: Henn, Kirsten
subject: ddc-570
subject: 570 Life sciences
description: As a consequence of current development in European chemical legislation, alternative methods in ecotoxicology gain more and more importance in chemical risk assessment. As an alternative to chemical testing with adult fish, the fish embryo toxicity test (FET) with Danio rerio is considered since a general correlation between both protocols is very high. However, for a couple of outliers the FET were less sensitive than the conventional fish test. To contribute to the clarification, to which extent protection of the embryo by the chorion is responsible for such deviations, the available information on the genesis and morphology, chemical composition, biological function and permeability of the fish chorion was reviewed under toxicological aspects. With regard to possible chemical interactions between chorion components and xenobiotics, there is still a need for supplementary research, particularly on understanding the function and properties of the pores which disperse across fish chorions. Nevertheless, it seems that the chorion is not a major barrier for ordinary chemicals; however, there are exceptions, like substances which might form complex or large structures with other similar molecules through chemical interactions such as ionic bonding (e.g. cationic polymers), substances which likely interact with SH-groups (e.g. heavy metals) or large molecules (e.g. polymers) are blocked by the chorion. For further investigations, existing dechorionation methods were evaluated on their applicability in toxicity testing. Thereupon a modified fish embryo test protocol with reproducibly high survival rates following removal of the chorion was established. The effect of dechorionation was demonstrated with the cationic polymer Luviquat HM552, which was thus shown to be blocked by the chorion of intact eggs probably due to its high molecular weight of ~400000 Dalton, but becomes strongly toxic after dechorionation. A “critical” molecular size might lie between 2000 and 3000 Da as demonstrated with experiments using polyethylene glycols. However, a reasonable molecular size cut off value could not be determined, since beside the molecular weight in Dalton or g/mol, a number of other factors contribute to the actual size of a molecule. In order to evaluate if differential uptake, accumulation or metabolization of the test compounds may produce differences between the results of acute fish and fish embryo toxicity, a known outlier, KCl, was investigated in comparison with other potassium and sodium salts in the standard as well as in the prolonged FET, in tests with eleutheroembryos and dechorionated embryos. Results were compared to acute fish toxicity data retrieved from the US EPA Ecotoxicity database and other data on larval toxicity available from the open literature. The results confirmed that the period around hatching is a critical stage during embryogenesis, which should be included in the testing procedure for chemical testing.
date: 2011
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/12998/1/Henn_Kirsten_Dissertation_2011.pdf
identifier: DOI:10.11588/heidok.00012998
identifier: urn:nbn:de:bsz:16-opus-129989
identifier:   Henn, Kirsten  (2011) Limits of the fish embryo toxicity test with Danio rerio as an alternative to the acute fish toxicity test.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/12998/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng