If the test compound found toxic during acute fish toxicity testing (OECD 203), chronic toxicity data required for registration of chemical. Fish early life stage toxicity test has been developed to assess the lethal and sub-lethal effects of chemicals on the early developmental stages of fish.
The early life stages of fish and invertebrates are more sensitive to toxicants than the adult organisms (Herkovits et al,. 1997, Hutchinson et al., 1998, Mohammed et al., 2009). As per the available literature on the calculated of no observed effect concentration (NOEC) values for the fish, it is observed that the larvae are more sensitive than the embryos for 68% of the tested chemicals. The sensitivity of fish larvae is ≥83% that of the juvenile fish for 83% of the tested chemicals. If the test compound found toxic during acute fish toxicity testing, chronic toxicity data required for registration of chemical. Fish early life stage toxicity test has been developed to assess the lethal and sub-lethal effects of chemicals on the early developmental stages of fish.
Study Design
Test organisms: Danio rerio (Zebrafish)
Test Procedure
Fertilised embryos (before beginning of gastrulation) are exposed to the range of concentrations of the test item dissolved in water. Study initiates by placing fertilised embryos in the test vessels. The duration of test is 30 days post-hatch.
Initially embryo is maintained in petri dish before hatching. Once larvae are hatched up to 90%, they are transferred into glass beakers and maintained until the end of the study.
Test medium is renewed based on the stability data of the test item. The stability of the test item in test medium is generated before conducting the experiment. The stability of test item is established for 24 and 48 h.
During the test, dissolved oxygen, pH, and temperature should be recorded in all the test vessels before and after every renewal. Total hardness and salinity should be measured at the beginning and end of the study, if required.
Test medium is analysed weekly for test item active ingredient concentration and stability before and after renewal.
Observations
During the test period, the eggs and larvae are observed daily for survival, hatching, abnormal appearance, and behaviour.
At the end of the study
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Individual length of the surviving juvenile fish is measured
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Body weight [wet weight (blotted dry)] of each replicate is record.
Endpoints
The lethal and sub-lethal effects (body length and body weight) are assessed and compared with that of control values to determine the median lethal concentration, the lowest observed effect concentration (LOEC) and the no observed effect concentration (NOEC). Alternatively, data may be analysed using a regression model in order to estimate the concentration that would cause a given percentage effect (i.e., LC/ECx where x is a defined % effect).
Guideline and Literature
OECD Guideline for Testing of Chemicals, No. 210: “Fish, Early-life Stage Toxicity Test“, adopted July 26, 2013
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