Secret of the Pacific Cleaner Shrimp: Scientists Uncover Its Ability To Display Bright White Stripes

White light is the product of combining all the colors in the visible spectrum. In generating white color, the photons of all wavelengths need to be scattered to be absorbed by the eye of the observer. Although this phenomenon is commonly observed in the surroundings, it can only be easily achieved in thick materials.

Scientists are baffled by a fundamental question in light scattering concerning the way white color is obtained from thin layers of materials. Understanding this occurrence will also provide insight into the property of the white skin membranes of organisms such as marine animals.

Uncovering the Secret of the Pacific Cleaner Shrimp

One of the striking species in the ocean is the Pacific cleaner shrimp, also known as scarlet cleaner shrimp and skunk cleaner shrimp. It derived its name from its diet composed mainly of dead tissue and parasites removed from fish, playing a vital role in the coral reef ecosystem.

Pacific cleaner shrimps are known for their brightly colored bodies containing a red band on each side, separated by a white line down the middle. Recently, an international team of scientists investigated the complex biological engineering behind this brilliant white color in the body of Pacific cleaner shrimp.

Researchers led by Dr. Ben Palmer from the Ben-Gurion University of the Negev investigated the white cuticle of this animal using cryo-scanning electron microscopy. The white tissues from the shrimp were deep-frozen and then blasted with focused beams of electrons. Upon interacting with atoms, the tissues produced signals converted into nano-scale images.

The result of the study suggests that ultra-thin layers of birefringent nanospheres create a brilliant white color in Pacific cleaner shrimp. The cells of the shrimp are packed with spherical particles that are 300 nanometers wide. Each particle contains layers of molecules organized in spokes to overcome optical crowding. This prevents the fall of light reflectance when the light-scattering structures are densely packed.

Effect of Depth on the Color of Marine Animals

According to NOAA Ocean Exploration, the color of marine animals is affected by regular patterns by the depth and the ability of the animal to blend in with its surroundings. Depth is most likely associated with light's capacity to penetrate the water's deep regions.

The distance that light particles can travel or photons differs in air and water. In the ocean, about 50% of the visible light energy is absorbed by water within the first 10 meters. As you go deeper beyond 200 meters, much light is rarely observed.

Reflection affects how an object appears white. In the deep regions of the ocean, there are fewer particles of light to reflect, making it very difficult to generate a brilliant white color. Each color also has specific wavelength ranges, making it difficult for other colors to reach the bottom of the ocean. As the wavelength gets shorter, the energy possessed by the color of light gets higher, affecting their ability to penetrate water. Red light has the longest wavelength but the lowest energy, so it is quickly filtered and almost does not reach the deep regions. On the other hand, blue light has the shortest wavelength and highest energy, allowing it to penetrate the depths of the water.