The zebrafish as a model organism

The zebrafish Danio rerio was already considered a popular ornamental fish in the 20^th century. When the breeding of homozygous zebrafish succeeded, it was thus also used for the first time in research in the context of genetic studies.¹

This fish species originated in the South Asian region, more precisely in countries such as Pakistan, Nepal and Bangladesh, where it can be found in ponds and rice fields. There the zebrafish lives in schools and feeds on smaller insects and crustaceans. They can be identified by their golden color with shimmering blue-black stripes running lengthwise from head to fin tip. Their maximum length is five centimeters. Females can be distinguished from their male counterparts by their slightly rounded belly. An adult female zebrafish can lay up to 300 eggs per week. Embryonic development and the life cycle as such progresses rapidly. Sexual maturity is reached within 16 weeks.^1,2

For many reasons, the zebrafish is well suited for use in research. Its biology and way of life alone ensure that it does not require too much effort to keep. Advantages are for example the group-holding, the undemandingness concerning the water quality, as well as the fast and numerous reproduction. Due to their transparency and development outside the womb, both embryos and larvae of zebrafish are well suited for various purposes.^1,3

From the animal experiment statistics of the year 2021, published by the Austrian Federal Ministry of Education, Science and Research, it can be seen that out of a total of 218,244 experimental animals, 24,463 zebrafish were used. Thus, this fish species is on the second place of all species used in research (place 1: represents the mouse with 165,884 animals used).⁴

Given the statistics, it can be concluded that Danio rerio is well suited as a model organism in research. As a vertebrate, the zebrafish genome is highly similar to that of humans. There is about 70% similarity in genetics and more than 80% of human disease-causing genes are also found in zebrafish. All genetic data on Danio rerio can be found on the website "The Zebrafish Information Network" (ZFIN).^1,5

Due to its characteristics, the zebrafish offers scientists a wide range of possible applications. Because of its remarkable ability to regenerate various cell types and tissues, it is often used in studies of angiology, cardiology and neurology. For example, complete reconstruction of the fin has been observed after it has been detached. In pharmacological studies, water-soluble substances can be tested for toxicity or other side effects by mixing them with fish water. The rapid development and transparency of early developmental stages favor their use in embryology.¹

1) https://www.mpg.de/10886445/zebrafisch, accessed Feb. 28, 2023.
2) Eisen, Judith S. "History of zebrafish research." The zebrafish in biomedical research. Academic Press, 2020. 3-14.
3) Sneddon LU. Where to draw the line? Should the age of protection for zebrafish be lowered? Altern Lab Anim. 2018 Dec;46(6):309-311. doi: 10.1177/026119291804600605. PMID: 30657327.
4) https://www.bmbwf.gv.at/Themen/Forschung/Forschung-in-%C3%96sterreich/Services/TierV/TVStat.html, accessed Feb. 28, 2023.
5) https://zfin.org/, accessed Feb. 28, 2023.

Hematopoiesis model: Gore AV, Pillay LM, Venero Galanternik M, Weinstein BM. The zebrafish: A fintastic model for hematopoietic development and disease. Wiley Interdiscip Rev Dev Biol. 2018 May;7(3):e312. doi: 10.1002/wdev.312. Epub 2018 Feb 13. PMID: 29436122; PMCID: PMC6785202.

Orthopedic model: Busse B, Galloway JL, Gray RS, Harris MP, Kwon RY. Zebrafish: An Emerging Model for Orthopedic Research. J Orthop Res. 2020 May;38(5):925-936. doi: 10.1002/jor.24539. Epub 2019 Dec 12. PMID: 31773769; PMCID: PMC7162720.

Inflammation Model, Drug Discovery: Zanandrea R, Bonan CD, Campos MM. Zebrafish as a model for inflammation and drug discovery. Drug Discov Today. 2020 Dec;25(12):2201-2211. doi: 10.1016/j.drudis.2020.09.036. Epub 2020 Oct 6. PMID: 33035664.

Oncology model: Etchin J, Kanki JP, Look AT. Zebrafish as a model for the study of human cancer.

Norecopa: https://norecopa.no/species/fish/zebrafish/