Mantis Shrimp

Mantis Shrimp

Biological Hammer Fists of death

Miguel Enrico S. Acuin

4th year BS Biology

You're diving out for the first time into the deep ocean blue. After just receiving your license for scuba diving, you decided it is high time to apply the skills that you have learned. You take your gear and settle on a subtropical location near Hawaii to view the marine biomes, hidden from the eyes of those stuck on land. With only the slightest hint of hesitation, you descend from the boat and marvel at the sights of the ocean deep. As you descend lower, low enough to touch the corals you notice a brightly colored crustacean sink its head into back into a hole. Curiosity takes the better of you and you approach the hole, peering into it you see nothing. Forgetting a crucial rule when exploring the ocean, you try to stick your finger into the hole to entice the creature. You suddenly let out a small yelp of pain as something cracks hard against your finger, something small and fast. Congratulations! You just learned first hand why mantis shrimp are “handled with care”

Figure 1. Mantis shrimp ^[1]

Mantis shrimp or stomatopods are colorful crustaceans belonging to the tropical-subtropical seas in the Indian and Pacific ocean as well as the temperate waters of the Atlantic ocean. They are colorful creatures with specialized raptorial appendages with the capability of generating 500 newtons of force in less than 1.5 milliseconds^[2]. To compare a blink is somewhere between 100-400 milliseconds and 500 newtons is around 60 kilograms worth of force. The physical energy that is released by these 38 cm creatures can be compared to that of a bullet leaving a gun. But you have to remember, this creature does this amazing feat of strength underwater, where you have to struggle to take a single step. Mantis shrimps hit their appendages so fast that they vapourize the water around the limb creating a bubble of super heated gas that collapses near their prey, instantaneously killing them ^[3]. This is a phenomenon called cavitation. You know what else causes cavitation?

Figure 2. Boat Propeller showing cavitation ^[4]

Thats right, boat propellers, things that make these huge hunks of steel move on the surface of the water. In fact, cavitation is so strong that it greatly damages the metal of the boat propeller over time. Fortunately, mantis shrimps are capable of shedding of their exoskeleton and regenerating the damaged limbs.

However, shotguns for limbs aren't the only thing fascinating about the mantis shrimp. Mantis shrimp have 11 classes of photoreceptors, pigments of a specific class of wavelength absorption specialized in the reception of light and its conversion into signals for the generation of sight ^[5]. Humans have two types, rods and cones and with just these two we have a photoreception system capable of making the colorful images we see around us. We can only begin to imagine what these 9 other classes are for.

Figure 3. What the coral reef might look like to a mantis shrimp ^[6]

Four photoreceptors however, have been shown to be capable of absorbing the wavelength of ultraviolet (315-380 nm). Not only are mantis shrimp capable of releasing an energy ball from its fists, but they are also equipped with what can only be described as super vision.

Mantis shrimp is considered a delicacy in numerous places. In the Philippines, it is cooked and eaten just like a normal shrimp while in Japan, its boiled as a topping for sushi or eaten raw as sashimi. In China its served with the name “pissing shrimp” with a tendency to shoot water when picked up and in the Mediterranean, it is a common sea food item. Mantis shrimp have been gaining a lot of popularity as seen in the comic strip from theoatmeal.com titled “Why the Mantis shrimp is my new favorite animal”^[7]. To end this post I would like to quote from the comic.

“The mantis shrimp is the harbringer of blood-soaked rainbows

It is bright

It is dark

It is beautiful”-The Oatmeal

References:

[1] life-sea.blogspot.com

[2] Patek, S. N., & Caldwell, R. L. (2005). Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp Odontodactylus scyllarus. Journal of Experimental Biology, 208(19), 3655-3664.

[3] Patek, S. N., Korff, W. L., & Caldwell, R. L. (2004). Biomechanics: deadly strike mechanism of a mantis shrimp.Nature, 428(6985), 819-820.

[4] www.thehulltruth.com

[5] Cronin, T. W., & Marshall, N. J. (1989). A retina with at least ten spectral types of photoreceptors in a mantis shrimp. Nature, 339(6220), 137-140.

[6] www.meipokwan.org

[7] theoatmeal.com/comics/mantis_shrimp