Identifying sublethal endpoints for evaluating neurotoxic compounds utilizing the fish embryo toxicity test

Area of Science:

• Aquatic toxicology
• Environmental science
• Ecotoxicology

Background:

• The fish embryo acute toxicity (FET) test is approved by the OECD but only estimates acute toxicity.
• The FET test may be less sensitive than other methods for certain neurotoxic compounds.
• Sublethal endpoints are being explored to enhance FET test sensitivity and predict adverse effects.

Purpose of the Study:

• Compare LC50 values from FET and larval growth and survival (LGS) tests for fluoride, nickel, and cadmium.
• Evaluate sublethal endpoints (growth, neurological, cardiovascular) for improving FET test sensitivity.

Main Methods:

• Compared FET and LGS test LC50 values for three neurotoxicants.
• Assessed sublethal endpoints including wet weight, snout-vent length, spontaneous contraction frequency, eye size, heart rate, and pericardial area.

Main Results:

• FET test showed higher LC50 values than LGS for fluoride and cadmium, indicating lower sensitivity.
• Cadmium exposure altered length, eye size, and pericardial area at concentrations five-fold lower than LC50.
• No significant alterations were observed for other tested endpoints or neurotoxicants.

Conclusions:

• The FET test is less sensitive for some neurotoxicants compared to the LGS test.
• Incorporating sublethal endpoints, like those observed with cadmium, can enhance FET test sensitivity.
• Further research with diverse neurotoxicants is needed to validate these sublethal endpoints for routine use.