Developmental toxicity of a compound purified from Fischerella 52−1. Within 3 dpf, zebrafish embryos exposed at 4- to 32-cell stage to 100 μg/mL of a pure compound isolated from Fischerella 52−1 (A) show a developmental phenotype characterized, in particular, by lack of melanophores, compared to control embryos (B) treated with solvent (i.e. CHCl3) only. Moreover, this phenotype is consistent for all embryos exposed to the toxin under a given set of conditions (e.g. toxin concentration, stage and line of fish).