Guest Blogger: Michelle Heim

The following guest post was voted best in the class for an undergraduate assignment on fish adaptation from Humboldt State University’s Fall 2021 Fish Conservation and Management course taught by Dr. Andre Buchheister. The assignment required students to find a peer-reviewed article on a fascinating fish adaptation or species and to communicate the scientific information in a blog format to a general audience. 

Not so deep down in the crystal-clear waters on the edge of the Indian and Pacific Oceans lurks an amazing creature. Truth be told, it’s one of the most colorful creatures in the ocean, boldly flashing a vibrant display. It doesn’t fear any predators and doesn’t need teeth, spines, claws, electricity, or camouflage to capture its prey. It’s only 10 inches long and it has its own special secret. It can punch with a force of 1,300 psi. That’s strong enough to fracture a metal boat propeller!

Meet the peacock mantis shrimp (odontodactylus scyllarus). While you may typically think of mantises of the ‘praying’ variety, the peacock mantis shrimp belongs to the taxonomic family subphylum Crustacea (crabs, shrimps, and relatives) and the order stomatopoda (mantis shrimps). There are more than 350 different species of mantis shrimp but the peacock mantis shrimp stands out for more reasons than just its flamboyant attire. It is one of the largest species of mantis shrimp that exists in the world, reaching an impressive 8 to 10 inches in length whereas other mantis shrimps only reach about 2 to 7 inches. It is also one of the longest-lived species. Peacock mantis shrimp can live for up to 20 years in both captivity and in the wild; most other mantis shrimps usually only live for 2-7 years. Lastly it is one of the strongest species. Some mantis shrimp species spear their prey, others smash their prey, the peacock mantis shrimp punches!

All the colors of the tide…

The peacock mantis shrimp lives in U-shaped burrows in the sand near the edge of coral reefs at depths of 3-40 meters (9.8-130 feet) within the Indo-Pacific Ocean, between Japan and Australia, and between eastern Africa and Guam.

And, it got its name with good reason. The exoskeleton of this critter is adorned with a swirling blend of rainbow colors, including bright red legs and underbelly, deep blue eyestalks, red and turquoise marbled mandibles, and a sea-green back. This conspicuous coloration may help the mantis shrimp to attract mates. It’s also clear to see that this shrimp isn’t too worried about being spotted by predators. In fact, its only predators are at the very top of the food chain – bluefin tuna, baracudas, and occasionally sharks, octopuses, and orca whales.

More than meets the eye

While humans only have 3 types of light-detecting cells, these shrimp have complex compound eyes that have between 12 and 16 different types of light-detecting cells. The band in the middle of their eyes allow them to  actually see polarization as well as deep ultraviolent (UVB) light! They are the only known creatures that can see polarized light. Light that bounces off of objects contains a polarized component, and seeing this polarization allows for these shrimp to find prey in their blue-tinged ocean environments. The ability to see polarization also helps them to see both bright and dark areas at once. Each eye can also be moved independently. Just imagine what those rainbow-colored exoskeletons look like to other peacock mantis shrimp!

A spring to action

While peacock mantis shrimp may appear peaceful within serene coral reefs, they hide a very deadly secret. These mantis shrimp can punch hard enough to kill. While they have 3 sets of legs for walking and 4 sets of legs for movement and predation, they have one very special set of legs that can punch hard enough to kill. These legs are greatly elongated second thoracic raptorial appendages on the front of their bodies, which is just a fancy way to say strong arms. These appendages utilize an incredible system not seen very often within the animal world. They use a power amplification system with a series of elastic springs, latches, and lever arms to pack one big punch. When the muscles contract, a click mechanism holds the limbs in place and the stored up elastic energy is held and released by a specialized spring mechanism. This movement can be equated to the drawback and release of a bow and arrow.

One powerful punch

With this specialized system, the peacock mantis shrimp can punch at an acceleration of 10,000 times the speed of gravity in just a few milliseconds and it does this while overcoming the resistance of the water that surrounds it. That’s the equivalent of more energy than the pistons in Formula One engines experience at the same acceleration as a .22 caliber bullet! This massive acceleration creates what’s called cavitation, where millions of tiny air bubbles generate heat and create a vacuum that water rushes to fill, causing stress fractures in surfaces. Just one ‘2.7mm bubble collapsing on a wall can generate over 9 megapascals of impact pressure, or 1,305 pounds of force per square inch’ (Patek and Caldwell 2005). That’s powerful enough to shatter and destroy rapidly spinning boat propellers (which they’ve been known to do!), or disturb one very unlucky crab… This mechanism allows the shrimp to hunt with very high success rates. They are strict carnivores and have to maintain a voracious diet of fish, mollusks, and aquatic crustaceans.

Peacock shrimp as pets?!?

Due to their striking coloration, these animals are sought after as pets. But – pet owners beware – they have a tendency to punch aquarium glass so hard that it shatters! Imagine coming home to an angry peacock mantis shrimp roaming around on your wet floor… yikes!

The peacock mantis shrimp is a mini but mighty creature. It has mighty eyes with 4 times the number of cones that humans have. It has a brightly colored exoskeleton that helps attract mates and warn potential predators. But its true shining armor is its punching raptorial appendages. Able to punch through material as tough as boat propellers, this little animal has created quite a niche for itself in the sandy tropical hollows that it calls home. Not many creatures can live up to the reputation of the peacock mantis shrimp. They truly are peacocks of a different feather!

For other Humboldt State student posts, please see:

• PACIFIC LAMPREY: SALMON’S UNDERAPPRECIATED NEIGHBOR by Erin Hanson
• MUDSKIPPIN’ ALONG by Luke Leuty
• THE HUMAN SIDE OF THE SHARK FIN TRADE by Kylie Holub
• FEELIN’ HOT HOT HOT by Ryan Stanley
• GOOD ADDITION? OR BAD INVADER? CHINOOK SALMON IN SOUTH AMERICA by Alexander Eaton
• CLEARLY, THE COOLEST FISH IN THE SEA by Justin Miller
• A PLATE OF LIES by Meghan Fox
• DANANANANANANANA BAT RAY by Angela Schmidt
• FROM REEF BANK TO FISH TANK: HOW THE AQUARIUM TRADE CAN IMPACT CORAL REEF CONSERVATION by Josh Cahill
• THE PEACEFUL BETTA by Joelle Montes

About the author:

My name is Michelle Heim and I’m a Fisheries Biology undergrad at Humboldt State University. I grew up in the small Sierra Nevada mountain town of Oakhurst, California. The outdoors has always been in my heart, spending most of my childhood hiking and exploring the wild world around me. I always knew I wanted to do my best to preserve our natural world for future generations and learned quickly that stream and river health is paramount to forest health. I worked as a Park Ranger for both the United States Army Corps of Engineers and for the Forest Service before being employed by Reedley College to maintain the Kings River that flowed by campus. I received my Associate of Science degree in Natural Resources from the small forestry school of Reedley College, and am now pursuing my Bachelor of Science degree in Fisheries Biology from Humboldt State. My goal is to work on expanding fish hatchery success for native trout and salmon populations as well as help bring about the existence of sustainable reproductive fish farm populations for our most overfished wild-caught species, including pollock and tuna (which are currently caught wild as juveniles and raised in farm pens).

References:

McHenry, M. J. 2012. When Skeletons Are Geared for Speed: The Morphology, Biomechanics, and Energetics of Rapid Animal Motion. Integrative and Compatitive Biology 52 (5) 588-596.

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

Oceana.org. 2010. Peacock Mantis Shrimp.

Chiu, F. 2013. Odontodactylus scyllarus. Animal Diversity Web, University of Michigan, Museum of Zoology, Michigan.

Patel, P. 2019. Camera Mimics Mantis Shrimp’s Astounding Vision. Scientific American 320, 2, 12.