How to Dissect Zebrafish: A Standardized Sampling Protocol for Histological and Molecular Studies in Adult Zebrafish

The zebrafish (<i>Danio rerio</i>) has become an essential model in fields such as developmental biology, toxicology, genetics, and regenerative medicine due to its low cost, small size, transparent embryos, and genetic similarity to humans. Nowadays, this model is increasingly recognized as a valuable tool in other fields, including veterinary medicine and animal production research, particularly aquaculture, due to its unique characteristics that make it suitable for studying economically significant diseases affecting production species. However, unlike established models such as mice, zebrafish lack standardized protocols for housing, feeding, anesthesia, and sample collection, which affects study reproducibility. In addition, it is a common practice to use whole zebrafish larvae or juveniles for metagenomic studies rather than analyzing individual organs, despite the fact that gene expression can vary between organs. This approach complicates the attribution of findings to specific biological processes. To address this, various authors proposed protocols for sample collection in larvae, juveniles, and adult zebrafish; however, comprehensive studies encompassing nearly all fish organs are scarce. Understanding zebrafish anatomy and the technical requirements of the study is essential for accurate sample collection. Some challenges present during zebrafish dissection include the small size of the fish, the fragility of their organs, and the faster onset of autolysis and heterolysis after the death of the animal. Using magnifying lenses, microdissection tools, and conducting dissections on cold surfaces can help mitigate these issues. This article aims to improve sample collection for histopathological and genetic studies in adult zebrafish by establishing a comprehensive, organized, and systematic dissection protocol that accounts for the anatomical specifics of this experimental model.