Anesthesia for fry?

Herwig Baier baier at JEEVES.UCSD.EDU
Wed May 29 19:38:32 EST 1996

Chi-Bin, the protocol you mention (from the Zebrafish Book) works nicely
under most conditions. However, I found that under the fluorescence
microscope the tricaine anesthesia is not deep enough: The larvae "wake up"
and twitch, probably because of the light-induced heating. One can, of
course, increase the tricaine concentration to 0.5mg/ml. This keeps the
larvae still, but also mostly kills them (at least in my hands).

Has anybody observed the same thing (and solved the problem)? Have other
anesthetics been tried (like urethane)?


>Yiing Lin asked:
>>I was wondering if anyone has worked out any protocol for anesthetizing
>>zfish fry and bringing them "back"?  I've been trying to take pictures of
>>fry which are live-stained and need long (1-2 minute) exposures, but they
>>move around much too much.
>At the risk of repeating what's easily found in the zebrafish book: Mesab
>(a.k.a. tricaine, MS-222, or 3-aminobenzoic acid ethyl ester) works fine as
>an anesthetic, and is readily reversible if you don't overdose the fish. A
>final concentration of 0.05 mg/ml (in embryo water or tank water) should be
>fine for larvae; if they're still twitching go up to 0.1 mg/ml. It's
>important to adjust the pH of your solution to about 7, as Mesab is an
>acid. It may also help to increase the viscosity of the medium, for
>instance by mounting the fish in 2-3% methylcellulose.
>--Chi-Bin Chien

Herwig Baier
baier at

University of California, San Diego
Department of Biology
La Jolla, CA 92093-0366

Phone: (619) 534-2526
Fax:   (619) 534-8866

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