Monday, 8 September 2014

New Darwinian Story: How the Zebrafish Got Its Stripes

A female zebrafish. Image courtesy of Azul, Wikipedia.

Joel Kontinen

British author Rudyard Kipling popularised the idea of the just so story. 1909 his collection Just So Stories for Little Children included tales like How the Leopard Got His Spots and How the Camel Got His Hump.

The paucity of fossils has prompted evolutionist to speculate on the arrival of countless features in the animal kingdom. A common denominator in these stories is that it would be difficult if not impossible to provide any real evidence for them.

They might be loosely built on discoveries, but often speculation takes over when facts end.

The title of a recent report by on researchers at the Max Planck Institute already suggests the genre of the story: How the zebrafish gets its stripes.

Scientists led by Nobel laureate Christiane Nüsslein-Volhard discovered that it takes three major pigment cell types (black cells, reflective silvery cells, and yellow cells) to give zebrafish their characteristic colour and pattern:

While it was known that all three cell types have to interact to form proper stripes, the embryonic origin of the pigment cells that develop the stripes of the adult fish has remained a mystery up to now. Scientists of the Max Planck Institute for Developmental Biology in Tübingen have now discovered how these cells arise and behave to form the ‘zebra’ pattern.”

So far, they conducted good operational science. However, then the report deteriorated into speculations:

“Their work may help to understand the development and evolution of the great diversity of striking patterns in the animal world.”

From zebra fish they first go on to extrapolate to other fish and then to other animals that likewise have spectacular patterns on their feathers or skin.

The authors speculate that variations on these cell behaviours could be at play in generating the great diversity of colour patterns in fish. ‘These findings inform our way of thinking about colour pattern formation in other fish, but also in animals which are not accessible to direct observation during development such as peacocks, tigers and zebras’, says Nüsslein-Volhard – wondering how her cats got their stripes.”

Compared to the real issue of the origin of zebrafish, tigers and zebras, this kind of speculation is rather trite.


How the zebrafish gets its stripes. Max Planck Gesellschaft. August 28, 2014.