Animal research ethics debate

Parallel scenario (not today's prompt): A lab wants to use zebrafish embryos to screen a new heart drug for toxicity before any human volunteers take it. Should that be allowed?\n\nClaim: I support the careful use of zebrafish embryos to screen a new drug for toxicity before human testing begins.\n\nEvidence (one justification): Zebrafish embryos are transparent and develop outside the mother, so scientists can watch the heart and other organs form in real time and see harmful effects early. Zebrafish also share many of the same organ systems and genes as humans, and running an early toxicity check in embryos flags dangerous compounds before they ever reach a human volunteer or a larger, more complex research animal.\n\nReasoning: Because zebrafish biology overlaps with human biology, a toxic effect seen in the embryo is a meaningful warning sign, and catching it early protects both future patients and other animals from unnecessary harm. That link between the model and the human question is what makes the test worth doing.\n\nGenuine ethical concern I acknowledge: Zebrafish embryos are still developing living organisms, and a result in a fish does not always predict what happens in a person, so a drug could look safe in the embryo and still harm humans, or look harmful and be dropped for the wrong reason. Because of that, I think embryo screening should follow clear welfare limits, use only as many embryos as the question requires, and be reported honestly about what the model can and cannot show.