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Do hippos sweat blood?


One of mythes says hippos sweat blood. Their skin excretes a special colourless liquid that turns red within minutes and then gradually goes brown. The hippo produces this exudation practically all the time but the largest amount is produced when the animal is ashore. This led to a generally regnant supposition that it's a kind of sweat to which blood soaks through and that this way the hippo cools itself down. Now the Japanese discovered what in fact the red substance is.

The team of Kimiko Hashimoto from Kyoto Pharmaceutical University, Japan, didn't put up with the image of bloody sweat and started to swab the red stains of two hippos from Ueno Zoo in Tokyo. When the gauze, which they wiped the hippos with, got damp with a sufficient amount of the hippo make-up, they performed a chemical analysis. They found out that the secretion is neither blood nor sweat but a mixture of pigments produced by cells in a hippo's skin. The exudation contains two pigments - red and orange. These substances, that give hippos their red appearance, were named hipposudoric acid (the red pigment) and norhipposudoric acid (the orange pigment).

When the Hashimoto's team searched for the function of the coloured secretion, they found out that, besides cooling, it serves as protection from sunshine and even manages to protect from bacterial infection. The mentioned pigments don't have just the ability to filter out the dangerous ultraviolet radiation but it was also proved during some lab tests that they obstruct growing of infectious bacteria. And it all seems to fit together - hippos live in Africa spending a lot of time directly in the sun. Then it's logical that a mechanism of protection from UV radiation has evolved in them. It's known that hippos are irritable and that their furious fights cause them a lot of wounds. For infection, every wound is a potential entry into the organism. In such cases the antibacterial effect of the secretion can come in handy to animals that like to wallow in potentially infectious mud.

The discovery of the function and structure of the red pigments will certainly become an interesting theme for cosmetics companies. The mentioned red and orange pigments could be classified as "natural products." Their antibacterial effects are also desirable. It's just not clear how the advertising agencies would cope with that it's a hippo product. But maybe such make-up of "hippo skin" would be very successful among people...


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2007 - 2014,  Tomas "Hroch"   |  Print article Print article