From the pinks and pastels of Valentine’s Day to the royal purples, greens and golds of Mardi Gras, the celebrations of February certainly do not lack for color. The same can be said of the mantis shrimp. If you are a fan of invertebrates, you most likely are familiar with these awesome crustaceans. They are undoubtedly some of the most charismatic and coolest animals in the ocean.
The term mantis shrimp is the common name for animals of the order Stomatopoda, which contains nearly 500 known species (with many more to discover, see below). Stomatopods can range in color from neutral browns to incredible neon hues that would make them at home in a Carnival parade. But the neatest color story when talking about mantis shrimp isn’t their color, it’s the way that they see color. Human eyes have three types of color photoreceptors (cones cells), each of which specializes in detecting one small range of visible light, or color, for a total of three colors.
These three cone cell types are described as “L” for long wavelengths (which corresponds roughly to red), “M” for medium wavelengths (roughly green), and “S” for short wavelengths (roughly blue). By combing these three cell types, much like the combination of red, green, and blue pixels creates the image on a TV screen, humans can perceive the entire range of color, or visible light, that we experience in our daily lives. Just think of the beautiful color palette in a sunset!
However, the eyes of mantis shrimp far surpass the vision capabilities of humans. Instead of three types of color-sensitive photo receptors, mantis shrimp have 12! Some of these receptors are even sensitive to light in the ultraviolet range, which is outside the visible light spectrum for humans. Even so, mantis shrimp don’t necessarily see color in more detail than humans. New research shows that their ability to discriminate between hues is limited. Unlike human vision where adjacent spectra are compared, in the eye of the mantis shrimp, each of the 12 photoreceptors picks up a specific color and identifies only that color. Overall, this makes the eye of the mantis shrimp less sensitive to color variations than humans, but it also requires less brain processing power. On top of all that, mantis shrimp can see polarized light. These advanced eyes have even inspired the development of new camera technology for detecting cancer.
If these critters’ awesome eyes didn’t already sound as awesome as a super-hero, they pack a punch that would put Superman to shame! Mantis shrimp are fierce hunters and have two raptorial appendages on the front of their body. The morphology of these appendages separates the mantis shrimp into two groups, smashers and spearers.
They use these weapons to hunt in exactly the way their names suggest—by smashing or spearing their prey. In fact, mantis shrimp have the fastest strike in the animal kingdom. Their blows can reach a peak velocity of 23 meters per second (75 feet per second), and can accelerate at speeds of 104 kilometers per second2 (65 miles per second2). The strike takes on average about 2.7 milliseconds. For comparison, blinking your (human) eye takes about 100-400 milliseconds. In that one blink, a mantis shrimp could have smashed or speared its prey 100 times!
These shrimp pack quite a punch as well, striking with 1500 newtons (or about 337 pounds of force). For comparison professional boxers hit with about 5000 newtons.The blows are strong enough to easily break through the shells of prey, and have even been known to crack aquarium glass.
The blistering speed of the shrimp’s strike causes the water in front of the claw to vaporize, creating a cavitation bubble. Cavitation is a phenomenon that happens when liquid is subject to rapid changes in pressure causing the formation of a vapor cavity in the liquid that subsequently implodes, resulting in a violent shockwave. The prey of mantis shrimp are subject to a one-two punch, the blow itself and the shockwave that follows. This shockwave may be enough to stun prey on its own, even if the prey manages to dodge the initial strike. high-speed video of these animals in action. In light of the extreme forces placed on the raptorial appendages of the mantis shrimp, these structures are surprisingly hardy. Their composition has even been studied in order to try and improve combat body armor for soldiers.
But mantis shrimp are lovers as well as fighters. Over a lifetime, one mantis shrimp can have twenty to thirty breeding seasons. Mantis shrimp show a range of complex behaviors related to breeding, including the use of florescent signaling patters and ritualized fighting. Specific mating behaviors, vary by species. Some species are quite promiscuous, while other species are serially monogamous, staying with one partner for a breeding cycle. A hand-full of species have even been reported as being long-term socially monogamous, staying with one partner for longer than one breeding cycle. In fact, the genus Pullosquilla not only shows long-term monogamy but biparental care of the eggs. In other words, both the male and female shrimp parents will assist in looking after the eggs, which is extremely rare in crustaceans. Monogamous mantis shrimp may work together in other ways as well, such as living in the same burrow and sharing hunting duties.
Mantis shrimp are diverse and extraordinary creatures, and we still have a lot to learn about them. A recent study by NMNH collaborator Paul Barber and Sarah Boyce found that Indo-Pacific stomatopod diversity is severely underestimated. One thing is certain they make our oceans a little more colorful!
By Frances Farabaugh, Intern Invertebrate Zoology Department NMNH
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