Mantis shrimp use natures sunblock to see UV news.sciencemag.org/biology/2014/07/mantis-shrimp-use-natures-sunblock-see-uv The colorful little guy pictured above puts the eyes of every other animal to shame. Whereas humans receive color information via three color receptors in our eyes, mantis shrimp (Neogonodactylus oerstedii) have 12. Six of these differentiate five discrete wavelengths of ultraviolet light, researchers report online today in Current Biology. The mantis shrimp’s vision is possible by making use of specially tuned, UV-specific optical filters in its color-detecting cone cells. The optical filters are made of mycosporine-like amino acids (MAAs), a substance commonly found in the skin or exoskeleton of marine organisms. Often referred to as nature’s sunscreens, MAAs are usually employed to protect an organism from DNA-damaging UV rays; however, the mantis shrimp has incorporated them into powerful spectral tuning filters. Though the reason for the mantis shrimp’s complex visual perception is poorly understood, one possibility is that the UV detection could help visualize otherwise difficult-to-see prey on coral reefs. Many organisms absorb UV light—these organisms would be easy to spot as black objects in a bright world. - With biological sunscreen, mantis shrimp see the reef in a whole different light eurekalert.org/pub_releases/2014-07/cp-ws062614.php In an unexpected discovery, researchers have found that the complex eyes of mantis shrimp are equipped with optics that generate ultraviolet (UV) color vision. Mantis shrimps six UV photoreceptors pick up on different colors within the UV spectrum based on filters made from an ingredient other animals depend on as built-in biological sunscreen, according to research reported in the Cell Press journal Current Biology on July 3. The mantis shrimp visual system contains six types of photoreceptors functioning completely outside the visual range of humans, says Michael Bok of the University of Maryland Baltimore County. Surprisingly, they produce their six UV photoreceptors using only two types of visual pigments by pairing one visual pigment with one of four UV filters. The UV filters block certain wavelengths of light from reaching the photoreceptors, chromatically shifting their sensitivity. The filters are composed of so-called mycosporine-like amino acids (or MAAs), which are commonly found in the skin or exoskeleton of marine organisms, where they absorb damaging UV rays. They do the same thing in mantis shrimp eyes, but for an entirely novel purpose. The effect is akin to putting red-tinted glasses over your eyes that block other wavelengths of light, except this is being done at the photoreceptor cellular level in shrimp, Bok explains. Exactly why mantis shrimp need such a sophisticated visual system remains mysterious, Bok says. Mantis shrimp use their eyes to navigate and spot predators and prey on the vibrant reef that is their home. Mantis shrimp also have complex social interactions that are likely mediated by distinct visual signals on their bodies. Their complex eyes, which include 16 or more types of photoreceptors in all, may provide them with a complex color and polarization visual system without a big brain to post-process lots of information. In other words, their eyes may sense and respond to complex visual inputs without the need to think very hard about it, Bok explains. Despite the new discovery, the researchers say, its still tough to imagine the reef as mantis shrimp see it. The way their eyes are built and how visual information is processed in their brains is so fundamentally different [from] humans that is very difficult to conceptualize what the world actually looks like to them, Bok says. Reference Biological Sunscreens Tune Polychromatic Ultraviolet Vision in Mantis Shrimp Current Biology 10.1016/j.cub.2014.05.071 cell/current-biology/abstract/S0960-9822(14)00672-1 Highlights •Mantis shrimp have only two UV visual pigments in their retinas •Four types of UV optical filters are found in specific facets of the compound eye •The four UV filters and two visual pigments combine to tune six receptor types •The filters are composed of pigments akin to biological sunscreens Summary Stomatopod crustaceans, or mantis shrimp, are renowned for their complex visual systems. Their array of 16 types of photoreceptors provides complex color reception, as well as linear and circular polarization sensitivity. The least-understood components of their retina are the UV receptors, of which there are up to six distinct, narrowly tuned spectral types. Here we show that in the stomatopod species Neogonodactylus oerstedii, this set of receptors is based on only two visual pigments. Surprisingly, five of the six UV receptor types contain the same visual pigment. The various UV receptors are spectrally tuned by a novel set of four short- and long-pass UV-specific optical filters in the overlying crystalline cones. These filters are composed of various mycosporine-like amino acid (MAA) pigments. Commonly referred to as “nature’s sunscreens,” MAAs are usually employed for UV photoprotection, but mantis shrimp uniquely incorporate them into powerful spectral tuning filters, extending and diversifying their preeminently elaborate photoreceptive arsenal.
Posted on: Sun, 13 Jul 2014 00:51:17 +0000
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