Fig. 1. Developmental toxicity of Oscillatoria 48-3 extracts. All embryos shown (A–E) are 1 dpf. Within 1 dpf, zebrafish embryos exposed at 4- to 32-cell stage to chloroform extracts (20 μg/mL) of Oscillatoria 48-3 (A–C) arrest development at mid-blastula transition (MBT; A), or are slow to progress to gastrulation (B), compared to control embryos treated with solvent only (E). In some cases, embryos develop beyond gastrulation (C), but are notably slowed compared embryos treated at the same time with solvent only (E). Embryos treated at MBT (D) developed normally as solvent controls (E).

Fig. 2. Developmental toxicity of Plectonema 33-7 and Tolypothrix 30-1-4 extracts. Within 2 dpf, zebrafish embryos exposed at 4- to 32-cell stage to 50 μg/mL of chloroform extracts from Plectonema 33-7 (A, B and D) and 100 μg/mL of chloroform extracts from Tolypothrix 30-1-4 (F), respectively, show inhibition of pharyngulation, including organogenesis (e.g. formation of the eye) and general cell-differentiation, compared to embryos treated with either 50 μL CHCl₃/mL of ERS (C and E), as solvent-only control for A, B and D, or 100 μL of CHCl₃/mL of ERS (G), as solvent-only control for F. In the case of Plectonema 33-7, there is additionally an apparent lack of migration of melanophores from neural crest (B) relative to the solvent-only control (C and E). Note: D and E are the same magnification.

Fig. 3. Developmental toxicity of Calothrix 33-2 extracts. Within 4 dpf, zebrafish embryos exposed at 4- to 32-cell stage to 100 μg/mL chloroform extracts of Calothrix 33-2 (B) show morphological deformities, including pericardial and peritoneal edemas, as well as bent tails/body axes, compared to control embryos treated with solvent (i.e. CHCl₃) only (A).

Fig. 4. Developmental toxicity of crude extracts from Fischerella 52-1. Within 1 dpf, zebrafish embryos exposed at 4- to 32-cell stage to chloroform extracts of Fischerella 52-1 culture medium (left) show a developmental phenotype, termed “puffy” ,characterized by swollen appearance and general lack of pigmentation, compared to control embryos treated with solvent only (right).

Fig. 5. 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).

Marine and freshwater HABs associated with human and environmental health concerns

Species/genera and their toxins, as well as the associated targets and toxicoses, are given.

Isolates of freshwater cyanobacteria identified to produce developmental toxins in the zebrafish embryo assay

All strains were isolated, by standard microbiological methods (Rippka et al., 1979), from freshwater sources in South and Central Florida. Isolates were cultured and extracted in CHCl₃ and 30% EtOH, and evaluated for developmental toxicity, using 4- to 32-cell stage embryos, from 1 hpf to 6 dpf (see Materials and methods).