A study by the Max Planck Institute for Developmental Biology in Tübingen (Germany) has revealed the process by which zebrafish develop their striking coloration based on alternating blue and gold stripes. According to the researchers, the key lies in the interaction of three large types of cells – black, yellow and reflective silver – that are generated in the skin of the youngest specimens of these freshwater species and that, together, make up a mosaic of several layers.
Although it was already known that these three types of cells must interact for the color stripes to form, the study led by the Nobel laureate in Physiology and Medicine Christiane Nüsslein-Volhard is a pioneer in the discovery of the embryonic origin of these structures. Nüsslein-Volhard and his collaborators describe the drastic transformations that yellow cell shapes undergo and how they generate the pigmentation that underpins the fish’s blue and gold striped pattern. According to the researcher and co-main author of the study Prateek Mahalwar, this is an unexpected finding: ” The existence of these behaviors among cells has completely surprised us , since they represent a departure from what we already knew about the formation of the pattern of colors”.
Now the zebrafish could become a model to explain the genetic basis of animal development and expand the existing scientific knowledge on the formation and evolution of the diversity of chromatic patterns in other species of fauna such as zebras, tigers or cockatoos.
The study was based on the findings of previous work, also from the Max Planck Institute, published in the journal Nature Cell Biology last June. In this other work, young zebrafish specimens equipped with pigment cell precursors illuminated with fluorescent light were photographed daily for three weeks, allowing the scientists to track the multiplication and movements of each individual cell. Thus they discovered that the three types of pigment cells reach the skin of this fish from different origins . The yellow ones are generated in a population of pluripotent cells on the dorsal aspect of the embryo. Instead, the black and silver ones came from a small cluster of stem cells near the spinal cord. From this it can be deduced that yellow and silver pigment cells have the ability to alter their shape and color depending on where they are located. Thus, when the yellow ones congregate on top of the silver ones and cover them, they stain the strip a golden color, while they acquire a star shape when placed on top of the black ones. On the contrary, the silver ones are distributed more sparsely above the stripes, and give them a blue tone that contrasts sharply with the gold.
