Team:Aachen/Flamingos-H-Salinarum
Why flamingos are pink (and what the Microbe of the Year 2017 has got to do with it)
When thinking of flamingos, one primarily thinks of long legs and pinkish colour. But, depending on their living environment, flamingos of the same species might also be white-coloured. Why is that so?
Flamingos are often found in places where rarely any other vertebrate can survive. They live at salt lakes all over the earth, which are actually quite hostile to life. Because at 20 %, the salt content of these lakes is significantly higher than that of sea water (3-4 %). Due to some adaptations, flamingos are able to drink the water of salt lakes. They mainly feed on small living organisms such as crayfish or plankton. The decisive advantage is that there aren’t any fish in these lakes which could challenge the flamingos for food - because they can’t survive high salt contents.
But why are flamingos pink-coloured? Responsible for this phenomenon is, among others, the Microbe of the Year 2017: Halobacterium salinarum.
Behind the melodious name is a bacteria (more exactly: an archaea) which is capable of reproducing en masse. High salt contents and extreme UV radiation - absolute no-go’s for most living beings - don’t bother H. salinarum. Quite the contrary, being a halophile (salt-loving) organism it feels most comfortable here.
Now how’s that possible? As a survival artist, H. salinarum developed a range of special adaptation mechanisms. By adjusting its salt content to that of the water, the microbe is able to survive in extremely salty water. Furthermore, H. salinarum possesses a red pigment (bacterioruberin, which belongs to the carotenoids) which protects the DNA from damaging UV radiation.
And precisely this red pigment, which has actually just a protective function, gives salt lakes their distinctive, deep red colour. The more of H. salinarum there is in a lake, the redder its colouration.
Being at the bottom of the food chain, our bacteria are consumed by zooplankton and crayfish - which, subsequently, turn red as well due to the pigment. These organisms in turn are the main food source for flamingos living in salt lakes, so that’s how they absorb the red pigment. Thereby, over a longer period of time, the plumage of the birds turns pinkish.
Colourings like this can not only be found in flamingos: pumpkins, apricots and - unsurprisingly - carrots as well owe their colour to carotenoid pigments.
So it’s obvious why some flamingos are coloured white: their food doesn’t contain red pigments from H. salinarum, and therefore there’s no pinkish colouring. That’s often the case with flamingos living in zoos. If you still discover pink-coloured flamingos there, it’s for sure that pigments have been mixed into the food. Not only due to aesthetical reasons but because otherwise no offspring can be expected - for the simple reason that female flamingos accept only colourful partners.
