Friday is here, and the 'A Taste of Science for the Weekend' corner is back — number 64.
This time: the connection between pigments and genetic mutations, and an orange-colored shark.
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Pigments are molecules that absorb light at certain wavelengths and emit light at others.
In the human body, pigments are what give skin, eyes, and hair their color — but the reason they exist has nothing to do with color at all.
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The wavelengths of sunlight include UV radiation, which can destroy living cell nuclei upon impact.
The body synthesizes the pigment melanin in skin cells called melanocytes, and these pigments concentrate around cell nuclei to protect them from radiation.
Melanin absorbs wavelengths in the high-energy and ultraviolet (UV) range, causing the skin to darken. The higher the concentration of melanin, the darker the skin.
Prolonged sun exposure causes cells to produce more melanin in an attempt to protect themselves, which is why we tan.
The energy absorbed by melanin is converted into heat, but excessive radiation may still penetrate the cell nucleus, where it can cause uncontrolled changes in DNA that manifest as genetic mutations or cancer.
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Melanin is a dark pigment, but the human body also contains pigments in shades of yellow and red.
A small portion are produced by the body itself — such as hemoglobin — while the rest come from food.
The pigments that give various vegetables their orange color are called carotenoids, and the body extracts them both for UV filtering in the skin and as raw material for the production of vitamins.
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The orange-skinned, white-eyed shark seen in the video was spotted in the summer of 2024 off the coast of Costa Rica, and as far as is known, it is the first shark of this coloration ever observed.
The cause of its unusual color is a rare combination of albinism — an exceptionally low production of melanin — together with xanthism, a genetic defect that causes an abnormal accumulation of orange pigments. This case is the only one ever documented with both phenomena occurring simultaneously.
Shabbat Shalom ☺️
Video credit: National Geographic
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