Metallic blue fruits use fat to produce colour and signal a treat for birds

Researchers have found that a common plant owes the dazzling blue colour of its fruit to fat in its cellular structure, the first time this type of colour production has been observed in nature. I first noticed these bright blue fruits when I was visiting family in Florence. I thought the colour was really interesting, but it was unclear what was causing it Silvia Vignolini The plant, Viburnum tinus , is an evergreen shrub widespread across the UK and the rest of Europe, which produces metallic blue fruits that are rich in fat. The combination of bright blue colour and high nutritional content make these fruits an irresistible treat for birds, likely increasing the spread of their seeds and contributing to the plant's success. The researchers, led by the University of Cambridge, used electron microscopy to study the structure of these blue fruits. While there are other types of structural colour in nature - such as in peacock feathers and butterfly wings - this is the first time that such a structure has been found to incorporate fats, or lipids. The results are reported in the journal Current Biology .