Sonifying zebrafish biology

Biologists often analyse data about the cell biology of living animals to understand their development. A large part of this involves looking for patterns in the data to use to refine their understanding of what is going on. The trouble is that patterns can be hard to spot when hidden in the vast amount of data that is typically collected. Humans are very good at spotting patterns in sound though - after all that is all music is. So why not turn the data into sound to find these biological patterns?

In hospitals, the heartbeats of critically ill patients are monitored by turning the data from heart monitors into sounds. Under the sea, in (perhaps yellow) submarines, "golden ear" mariners use their listening talent to help with navigation and detect potential danger for fish and the submarine. They do this by listening to the soundscapes produced by sonar built up from echoes from the objects round about. This way of using sounds to represent other kinds of data is called 'sonification'. Perhaps similar ideas can help to find patterns in biological data? An interdisciplinary team of researchers from Queen Mary including biologist Rachel Ashworth, Audio experts Mathieu Barthet and Katy Noland and computer scientist William Marsh have been trying the idea out on the zebrafish. Why zebrafish? Well, they are used lots for the study of the development of vertebrates (animals with backbones). In fact it is what is called a 'model organism': a creature that lots of people do research on as a way of building a really detailed understanding of its biology. The hope is that what you will learn about zebrafish help you understand the biology of other vertebrates too. Zebrafish make a good model organism because they mature very quickly. Their embryos are also transparent. That is really useful when doing experiments because it means you can directly see what is going on inside their bodies using special kinds of microscopes.

The particular aspect of zebrafish biology the Queen Mary team has been investigating is the way calcium signals are used by the body. Changes in the concentration of calcium ions are important as they are used inside a cell to regulate its behaviour. These changes can be tracked in zebrafish by injecting fluorescent dyes into cells. Because the zebrafish embryos are transparent whatever has been fluorescently labelled can then be observed.

The Queen Mary team has developed software that detects calcium changes by automatically spotting the peaks of activity over time. They relied on a technique that is used in music signal processing to detect the start of notes in musical sequences. Finding the peaks in a zebrafish calcium signal and the notes from the Beatles' Day Tripper riff may seem to be light years apart, but from a signal processing point of view, the problems are similar. Both involve detecting sudden burst of energy in the signals. Once the positions of the calcium peaks have been found they can then be monitored by sonifying the data.

What the team have found using this approach is that the calcium activity in the muscle cells of zebrafish varies a lot between early developmental stages of the embryo and the late ones. You can have a go at hearing the difference yourself - listen to the sonified versions of the data.