The fishes that could unlock the secrets of the human body

29 Sep,2026

The fishes that could unlock the secrets of the human body

Scientists are turning to some of the zebrafish’s lesser-known relatives to answer fundamental questions about how organs grow and function, and why some animals can regenerate organs that humans cannot.

Picture a fish so small it fits on a fingernail, so transparent you can watch its organs working in real time. Now imagine using that fish to understand why some people’s brain function declines or muscles waste away with age, or how a damaged human heart might one day be coaxed into repairing itself.

That is the approach researchers at ARMI are taking, and the tools they are using are a group of small freshwater fish called danionins: the zebrafish and its closest relatives.

In a review published this month in Nature Reviews Genetics, the team of Dr Marco Podobnik, Dr Kevin Lu and Professor Peter Currie from ARMI, and Dr Uwe Irion from the Max Planck Institute for Biology in Germany, outline the case for this group of fish as one of biology’s most powerful research platforms.

Professor Currie, Director of Research at ARMI and senior author of the review, has spent two decades working with zebrafish.

“Zebrafish became indispensable in research because you can watch development happen in a living embryo,” he said. “Decades of work developing genetic tools that provided ways to switch zebrafish genes on and off, track individual cells and edit the genome gave scientists more ways to ask precise genetic questions in this species than in almost any other vertebrate.”

Dr Podobnik, a postdoctoral research fellow at ARMI who is the first and co-corresponding author of the review, worked with species that are closely related to zebrafish during his PhD and continues to explore the potential of fish biodiversity.

“The zebrafish is just one species,” he said. “Its relatives are remarkably diverse. By comparing developmental or regenerative processes between species, we can learn more about the different capacities to grow and regenerate organs. Now we have the tools to find out exactly which genetic alterations drive those differences.”

A question of growth

One of the review’s highlights concerns skeletal muscle. Unlike humans, fish continue adding brand new muscle fibres throughout their lives, a process called hyperplasia. But the rate at which they do this varies dramatically between species.

The tiny Danionella cerebrum – that near-transparent fingernail-sized fish, sometimes called ‘glassfish’ – stops adding new fibres early in development. The larger Devario malabaricus (also called ‘giant danio’) and the intermediate sized zebrafish continue adding new fibres at a high rate throughout their development.