{"id":15230873,"date":"2026-07-28T10:30:00","date_gmt":"2026-07-28T14:30:00","guid":{"rendered":"https:\/\/www.inthacity.com\/news\/analyze-this-how-sea-slugs-get-their-flashy-colors\/"},"modified":"2026-07-28T10:33:28","modified_gmt":"2026-07-28T14:33:28","slug":"analyze-this-how-sea-slugs-get-their-flashy-colors","status":"publish","type":"post","link":"https:\/\/www.inthacity.com\/news\/analyze-this-how-sea-slugs-get-their-flashy-colors\/","title":{"rendered":"Analyze This: How sea slugs get their flashy colors"},"content":{"rendered":"

In the sea, soft-bodied sea slugs crawl around without shells to protect them. Instead, they sport dazzling colors and flashy patterns to warn would-be predators that they\u2019re toxic<\/a>. Now, researchers have learned that many of these vibrant hues come from structures under the slugs\u2019 skin<\/a>.<\/p>\n

These slugs, called nudibranchs (NU-dih-branks), are sometimes dubbed the \u201cbutterflies of the sea.\u201d Their colors are \u201cexceptionally bright,\u201d says materials scientist and physicist Samuel Humphrey. He works at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany. Nudibranchs\u2019 range of colors and patterns exceeds those of other ocean dwellers and is only like that of butterflies and birds, he says.<\/p>\n

Not much was known about nudibranch colors, Humphrey says. But in nature, some of these colors \u2014 such as white, blue and purple \u2014 are hard to get from pigments<\/a>. (Those are molecules that provide color.) That made Humphrey\u2019s team suspect the slugs\u2019 colors instead arise from light waves bouncing off structures on their bodies. Such structural color<\/a> can create hues as intense as those seen on the sea slugs.<\/p>\n

\"left:
Two sea slugs \u2014 a Barbie-pink Hypselodoris bullockii<\/em> (left) and a golden-speckled Hypselodoris tryoni<\/em> (right) \u2014 use the same technique to wear wildly different hues.<\/span>Left: Reinhard Dirscherl\/Getty Images; Right: ifish\/iStock\/Getty Images Plus<\/span><\/figcaption><\/figure>\n

Humphrey collected one species of nudibranchs off the coast of France. Others, he and his colleagues bought from aquarium shops. The researchers looked at the creatures under the microscope and saw tiny dots of colors that combined to create a shade. For instance, a nudibranch might look purple, but zoom in, and you may find specks of red and blue. \u201cIt\u2019s a bit like mixing paints until you get the color you want,\u201d Humphrey says.<\/p>\n

Actually, he adds, \u201cit\u2019s better than that.\u201d Sea slugs\u2019 hues arise from specific wavelengths, or colors, of light<\/a> bouncing off them and reaching our eyes. And the team found that, for a given color, nudibranchs reflect up to 80 percent of light that hits them. That makes their hues more vivid than those produced by pigments, which create colors by absorbing light. Losing light means losing brightness, Humphrey explains.<\/p>\n

The researchers shared their results in the March issue of the Proceedings of the National Academy of Sciences.\u200b<\/em><\/p>\n

With a powerful microscope, the team saw stacks of tiny plates under nudibranchs\u2019 skin. The plates were crystals made of guanine. The thickness of the plates and the distance between them in a stack determined the colors that they reflected. That allows sea slugs to wear a rainbow of colors made of just one material.<\/p>\n

The many tiny dots of color on sea slugs\u2019 skin creates an effect akin to how TVs make images with many spots of only a few colors. This is called pixelation. \u201cIt feels like a thing that humans have invented,\u201d Humphrey says. \u201cBut actually, evolution had invented it millions of years ago.\u201d<\/p>\n

\n

Sea slugs’ style is spot on<\/h3>\n
\"\"
Humphrey et al\/PNAS 2026 (CC BY 4.0)<\/span><\/figcaption><\/figure>\n

Microscope images revealed close-ups of nudibranchs\u2019 skin (Figures A\u2013F). These images show the many dots of different hues that make up a single area of color on the animals. Researchers also measured how these areas interact with light (Figures I\u2013N). The graph in Figure I goes with the image in Figure A, Figure J goes with Figure B and so on. The graphs show the reflectance, or how much light reflects off differently colored spots to reach our eyes. Most colors have a specific wavelength at which the most light is reflected. For example, Figure C shows the pink region of Hypselodoris bullockii,<\/em> which has some violet colored dots (Figure C). These dots reflect the most light at a wavelength of around 400 nanometers (Figure K).<\/p>\n<\/div>\n

Data Dive:<\/h2>\n
    \n
  1. How many types of colored light make up the violet hue of Hypselodoris tryoni<\/em> (Figure A)?<\/li>\n
  2. How many types of colored light make up the beige or white region of the same slug (Figure B)? Which color of light has the highest reflectance? What is that color\u2019s peak wavelength?<\/li>\n
  3. Which sea slug here has the color with the highest reflectance? (Hint: Not all the y-axes are exactly the same.) What is that color and what is the peak wavelength?<\/li>\n
  4. How many different colors of light are in the region of Chromodoris annae<\/em> (Figures E and M)? Based on those colors, how do you think this area of the slug looks to the eye?<\/li>\n<\/ol>\n

    Source: Science \u2013 sciencenewsforstudents<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

    Crystals beneath the skin of nudibranchs, also called sea slugs, allow the creatures to make an array of intense hues with just one material.<\/p>\n","protected":false},"author":1,"featured_media":15230875,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false,"footnotes":""},"categories":[218],"tags":[],"class_list":["post-15230873","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science"],"featured_image_urls":{"full":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat.jpg",800,450,false],"thumbnail":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-300x169.jpg",300,169,true],"medium":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-620x349.jpg",620,349,true],"medium_large":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-768x432.jpg",768,432,true],"large":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat.jpg",800,450,false],"1536x1536":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat.jpg",800,450,false],"2048x2048":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat.jpg",800,450,false],"post-thumbnail":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat.jpg",800,450,false],"ignition_item":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-670x446.jpg",670,446,true],"ignition_item_lg":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat.jpg",800,450,false],"ignition_article_media":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-510x450.jpg",510,450,true],"ignition_minicart_item":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-160x160.jpg",160,160,true],"profile_24":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-24x24.jpg",24,24,true],"profile_48":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-48x48.jpg",48,48,true],"profile_96":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-96x96.jpg",96,96,true],"profile_150":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-150x150.jpg",150,150,true],"profile_300":["https:\/\/www.inthacity.com\/news\/wp-content\/uploads\/2026\/07\/15230873-1440_at_sea_slug_colors_feat-300x300.jpg",300,300,true]},"author_info":{"display_name":"news.iNthacity","author_link":"https:\/\/www.inthacity.com\/news\/author\/atombo\/"},"category_info":"Science<\/a>","tag_info":"Science","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts\/15230873","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/comments?post=15230873"}],"version-history":[{"count":1,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts\/15230873\/revisions"}],"predecessor-version":[{"id":15230874,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/posts\/15230873\/revisions\/15230874"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/media\/15230875"}],"wp:attachment":[{"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/media?parent=15230873"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/categories?post=15230873"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.inthacity.com\/news\/wp-json\/wp\/v2\/tags?post=15230873"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}