Cartilage and bone malformations in the head of zebrafish (Danio rerio) embryos following exposure to disulfiram and acetic acid hydrazide.

In order to investigate teratogenic effects, especially on cartilage and bone formation, zebrafish embryos were exposed for 144h to the dithiocarbamate pesticide disulfiram (20-320μg/L) and acetic acid hydrazide (0.375-12g/L), a degradation product of isoniazid. After fixation and full-mount staining, disulfiram could be shown to induce strong cartilage malformations after exposure to ≥80μg/L, whereas acetic acid hydrazide caused cartilage alterations only from 1.5g/L. Undulating notochords occurred after exposure to disulfiram even at the lowest test concentration of 20μg/L, whereas at the two lowest concentrations of acetic acid hydrazide (0.375 and 0.75g/L) mainly fractures of the notochord were observed. Concentrations of acetic acid hydrazide≥1.5g/L resulted in undulated notochords similar to disulfiram. Cartilages and ossifications of the cranium, including the cleithrum, were individually analyzed assessing the severity of malformation and the degree of ossification in a semi-quantitative approach. Cartilages of the neurocranium such as the ethmoid plate proved to be more stable than cartilages of the pharyngeal skeleton such as Meckel's cartilage. Hence, ossification proved significantly more susceptible than cartilage. The alterations induced in the notochord as well as in the cranium might well be of ecological relevance, since notochord malformation is likely to result in impaired swimming and cranial malformation might compromise regular food uptake.