Fast, easy and early (larval) identification of transparent mutant zebrafish using standard fluorescence microscopy

The availability of transparent zebrafish mutants (either TraNac : tra b6/b6 ; nac w2/w2 or casper: roy a9/a9 ; nac w2/w2 ) for live imaging studies together with the ease of generating transgenic lines are two of the strengths of the zebrafish model organism. The fact that transparent casper ( roy a9/a9 ;nac w2/w2 ) and silver nacre ( nac w2/w2 ) mutants are indistinguishable by eye at early stages (1-5 days post-fertilization; dpf) means many fish must be raised and later culled if they are not transparent. To identify translucent mutants early and easily at the early larval stage (≤5 dpf) before they are classified as protected animals, we developed a simple screening method using standard fluorescence microscopy. We estimate that this procedure could annually save 60,000 animals worldwide.