Mantis shrimp are captivating marine crustaceans known for their vivid coloration and remarkable visual capabilities. Though bearing the name “shrimp,” these creatures are not true shrimp but belong to the order Stomatopoda, displaying unique characteristics that set them apart in the underwater world. Their striking appearance, often a kaleidoscope of oranges, greens, reds, and blues, highlights their presence in tropical and subtropical marine environments.
The Unique Visual System
The mantis shrimp possesses a complex visual system, one of the most elaborate in the animal kingdom. Each of their stalked compound eyes moves independently, allowing them to scan their surroundings simultaneously. This unique eye structure is divided into three distinct regions: a dorsal hemisphere, a ventral hemisphere, and a specialized equatorial midband.
The midband consists of six parallel rows of specialized ommatidia, the individual visual units of a compound eye. Each ommatidium contains a cornea, a crystalline cone (lens), and a rhabdom (a transparent light sensor composed of eight photoreceptor cells). The arrangement of these photoreceptor cells within the midband, particularly in rows 1-4, allows for spectral photoreception, while rows 5 and 6 are specialized for circular polarization vision. This intricate anatomical design forms the biological foundation for their extraordinary perception of light.
Seeing Beyond Human Limits
Mantis shrimp can perceive light far beyond the scope of human vision. While humans have three types of photoreceptors for color detection, mantis shrimp can possess up to 12 or even 16 different types, enabling them to distinguish a vast array of colors, including those in the ultraviolet (UV) spectrum.
Beyond their extensive color perception, mantis shrimp are also capable of detecting polarized light, both linear and circular. They are currently the only known animals to possess circular polarization vision. This ability to analyze the orientation of light waves provides them with additional visual information about their environment, enhancing contrast and helping them discern objects that might appear camouflaged to other animals.
Color in Communication and Survival
Mantis shrimp use their vibrant colors and advanced vision for communication and survival. Their striking coloration, particularly on meral spots found on their raptorial appendages, is used for intra-species communication, including mating displays, territorial warnings, and distinguishing between species.
Their ability to perceive polarized light also aids in communication, as some species have body markings that reflect polarized light, which can be used to warn others about occupied burrows. Beyond communication, their specialized vision assists in hunting by enhancing contrast to detect camouflaged prey and in avoiding predators by interpreting subtle visual cues in their complex marine habitats.
Diversity in Mantis Shrimp Hues
Mantis shrimp coloration varies considerably across species. The specific hues and patterns often reflect their diverse habitats and behaviors. For instance, some species, like the peacock mantis shrimp, display brilliant combinations of orange, green, red, and blue, often with leopard-like spots.
Other species may exhibit more subdued coloration, such as golden mantis shrimp which can appear green in seagrass environments or tan in sandy areas, or rock mantis shrimp that range from dark green to black. This diversity is linked to their need for camouflage in different surroundings or to specific visual adaptations.