Adult zebrafish euthanasia: efficacy of anaesthesia overdose versus rapid cooling
- Published
- Accepted
- Subject Areas
- Aquaculture, Fisheries and Fish Science, Veterinary Medicine
- Keywords
- euthanasia, anaesthesia overdose, rapid cooling, adult zebrafish
- Copyright
- © 2018 Ferreira et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2018. Adult zebrafish euthanasia: efficacy of anaesthesia overdose versus rapid cooling. PeerJ Preprints 6:e27432v1 https://doi.org/10.7287/peerj.preprints.27432v1
Abstract
The rapid increase in zebrafish use needs to be accompanied by research into refinement of procedures, such as euthanasia. The EU directive lists three possible euthanasia methods for fish: anaesthetic overdose, electrical stunning and concussion. However, for a small fish like zebrafish, concussion and electrical stunning are difficult to perform, leaving anaesthetic overdose as the only realistic option. Thus, more tailored solutions need to be found for this small tropical water species. Our aim was to test the efficacy of different anaesthetics overdose and of the rapid cooling method to kill adult zebrafish. Adult mixed-sex AB zebrafish (n= 12) were randomly assigned to: 250mg/L MS222; 20 mg/L propofol + 100 mg/L lidocaine; 6 mg/L etomidate; 50 mg/L clove oil; rapid cooling (water at 2-4º C). Two minutes after opercular movement ceased, the animals were transferred to clean water to assess if they could recover. Zebrafish euthanized with rapid cooling ceased the opercular movements significantly quicker compared with the other groups, and etomidate-treated animals took longer to die. No zebrafish recovered after being placed in clean water. All protocols used were efficacious to achieve euthanasia, but rapid cooling was consistently the fastest and so more efficient. Further studies evaluating animal welfare and the quality of the biological samples are needed to refine the rapid cooling protocol before recommendations can be made to change legislation to include this as a method for euthanasia for small tropical fish.
Author Comment
Euthanasia is a routine procedure in laboratory animals used in research. The methods allowed by the European Directive to be used in fish may be limited to use in all fish species, as zebrafish. Thus, this work shows the efficacy of the overdose of different anaesthetics and rapid cooling method to kill adult zebrafish. This work will be submitted to a peer-review journal later-on. Some of these results were presented in the Nordic Zebrafish and Husbandry meeting 2018.
Supplemental Information
Supplementary file 1: Raw data
Latency to equilibrium loss, loss of painful stimulus-response and cease of opercular movement (sec) after different euthanasia methods.