The Painbow

Kelly’s Field Notes

Common Name: Mantis shrimp (“sea locusts” to the ancient Assyrians, “prawn killers” to Aussies, “thumb-splitters” to many)

Order: Stomatopoda

Family: Gonodactylidae, Hemisquillidae, Lysiosquillidae, Nannosquillidae, Odontodactylidae, Pseudosquillidae, Squillidae, Tetrasquillidae

Genera: There are 11 genera of mantis shrimp!

Species of Note (There are more than 250 species of mantis shrimp):

Peacock mantis shrimp (Odontodactylus scyllarus) - peacock mantis shrimp are one of the larger mantis shrimps, with a length of 3.0 - 18 cm (1.2 - 7.1 in). They are also one of the most colorful species. They are found in the Indian and Pacific Oceans.
Zebra mantis shrimp (Lysiosquillina maculata) - found in the Indo-Pacific region of the ocean, it is the largest mantis shrimp in the world with a body length of 40 cm (15.7 in).

Description:

While we call them mantis shrimp, they are not related to shrimp any more than other decapods (lobsters, crabs, shrimp). Mantis shrimp do not belong to order Decapoda, they belong to order Stomatopoda (“mouth foot” in ancient Greek). Mantis shrimp branched off of class Malacostraca around 340 million years ago, during the Carboniferous Period. Malacostraca contains all the usual crustacean suspects: crabs, lobsters, isopods, prawns, crayfish, etc. This is well before the dinosaurs!

Mantis shrimp have similar body plans to shrimp, prawns, and lobsters: long segmented abdomens, specialized front appendages, compound eyes. They generally move and swim as shrimp and lobsters do, though one species (N. decemspinosa) forward flips when stranded in areas too shallow to walk properly in. This species has particularly short legs!

Mantis shrimp eyes, which are on long stalks, are particularly interesting. The eyes can move independently of one another, capable of rotating in all three dimensions. While old research on mantis shrimp eyes assumed they had excellent color vision due to having 12 types of color cone photoreceptors (humans have 3), they actually can’t see incredible blends of colors like we can, they can only see 12 colors total. Mantis shrimp are unable to differentiate between colors that are close together in wavelength because they don’t have the neural capacity to process the signals activating across cones. Different cones are sensitive to different wavelengths of light, so when we see yellow all three of our cones will be activated. The mantis shrimp can only activate one cone at a time. What is interesting, is their ability to see UV (ultraviolet) and polarized light, which we cannot. Due to their lack of neural power, mantis shrimp have a dense arrangement of photoreceptors (ommatidia) lined up like a strip which process visual information as it comes in, removing some of the heavy lifting the brain would need to do. This band also splits each eye into three sections, allowing it to have depth perception as each eye has trinocular vision. The midband of the eye is used to detect shapes and movement.

Mantis shrimp also pay attention like no other crustacean! Primates and even some insects and spiders adjust their gaze rapidly to observe their environment and changes within it. This flicking back and forth allows the mantis shrimp to quickly focus on an area or organism of interest. Given their eyes move independently the mantis shrimp can do so in more than one location at once by focusing and following an object with the midband of the eye.

While we are not certain how the mantis shrimp uses polarized light detection, scientists suggest it could be to identify prey, sexual signaling, and other forms of communication that would not stand out to predators. For example, females are fertile during specific moon phases, some species males and females molt together during less luminous moon phases, and larval mantis shrimp only rise to the surface to feed during the new and first quarter moon (to hide from predators when vulnerable). This suggests even larval mantis shrimp have impressive eyes. Polarized light detection may also aid in depth perception, which would be necessary when hunting using fast claw movements.

Mantis shrimp front appendages:

All mantis shrimp have specialized front appendages (raptorial) used for hunting and fighting. These appendages are connected to an elastic mechanism found in the merus segment, which allows the mantis shrimp to strike with an acceleration of 10,400 g (102,000 m/s2 or 335,000 ft/s2) and speeds of 23 m/s (83 km/h; 51 mph). Think about a tight spring being released. This causes cavitation bubbles in the water, which collapse causing a second round of damage from the strike. This shockwave can stun or kill the target even if the raptorial appendage misses.

Mantis shrimp raptorial appendages come in a wide diverse variety of forms, but they generally fall into three categories: spear dactyls, club dactyls, and undifferentiated dactyls. Spear dactyls are long and have several small tips along the spear, this appendage type is used to catch evasive prey. Club dactyls have a thick club used to smash hard-shelled prey. Undifferentiated dactyls have a forcep used to dislodge and pull apart hard shelled prey. Club species have been shown to have a more potent spring mechanism than spearers or undifferentiated species.

Life Cycle:

A note about life cycle: Dr. Roy Caldwell is a well known researcher and expert on mantis shrimp, I’m going to use his description of the well documented split-thumb mantis shrimp (Neogonodactylus bredini) and N. oerstedii for this section, as covering all the species would not be helpful and there are so many we know very little about.

Mantis shrimp reproduce via internal fertilization (fertilizing the eggs while still within the female), then she lays them and either carries them around or keeps them in a burrow. In some species males and females only come together to mate and in others they remain in long-term monogamous pairs. They may breed 20 to 30 times in their lifetime. Once eggs hatch, larvae enter the plankton stage, floating through currents for about one month. After that time they settle in seagrasses. Mantis shrimp undergo several molts, increasing in size with each molt. At 6 months old they are 1.5-1.8 cm (0.6-0.7 in) in length, then at a year about 2.5 cm (1.1 in). Females are ready to reproduce at 2 years old, and are around 3.5 cm in length. They continue to molt and grow about 0.5 cm per year, with some found at over 50 cm (19.79 in) in length (likely between 6 and 7 years old). An adult weighs between 0.4-3.2 oz (12-90 g).

Mantis shrimp lifespan may differ between species, but it is generally somewhere between 1 and 5 years, though Dr. Roy Caldwell believes his lab had found a few that may have been as old as 6 or 7 years, based on their size. He also states he has kept zebra mantis shrimp (Lysiosquillina maculata) in captivity for 10 years, but he believes they may live as long as 25 or more years. Peacock mantis shrimp (Odontodactylus scyllarus) are the most common species found in aquaria, but are usually caught as adults so it is difficult to estimate their true lifespan. Dr. Caldwell suggests they may live for up to 6 or 7 years.

Mantis Shrimp Super Powers:

Raptorial strike - mantis shrimp can strike with an acceleration of 10,400 g! This is the fastest strike in the animal kingdom (about as strong as a .22 caliber bullet)! Enough to break aquarium glass, which does happen sometimes.
Cavitation stun - even if the strike misses the shock wave caused by the collapse of cavitation bubbles can stun or kill the target.
Super sight - mantis shrimp can see ultraviolet and polarized light!
Digging - mantis shrimp are excellent diggers, creating burrows to surprise their prey.
Signals - mantis shrimp use their antennal scales to signal to each other, sometimes to avoid an outright fight.
Rumbles - some species of mantis shrimp create low frequency grumbles. This may be to deter predators or rivals and/or to attract mates.
Fluorescence - many species of mantis shrimp have fluorescent yellow markings to add to threat displays both to each other and predators.

Mantis shrimp in Culture:

Mantis shrimp are common pets and found in aquariums. The rainbow mantis shrimp, in particular, is very popular.
Mantis shrimp are eaten in many cuisines, including Cambodia, Japan, Vietnam, the Mediterranean, the Philippines, and Kiribati.

Mentioned in This Episode:

References:

Anderson, P. S. L., and S. N. Patek. "Mechanical sensitivity reveals evolutionary dynamics of mechanical systems." Proceedings of the Royal Society B: Biological Sciences 282.1804 (2015): 20143088.

Caldwell, Roy (user name: Gonodactylus). “Lifespan of Common Mantis Species? - Reef Central Online Community.” Www.reefcentral.com, www.reefcentral.com/forums/showthread.php?t=2672753. Accessed 7 June 2024.

Cronin, Thomas W., et al. "Filtering and polychromatic vision in mantis shrimps: themes in visible and ultraviolet vision." Philosophical Transactions of the Royal Society B: Biological Sciences 369.1636 (2014): 20130032.

Feller, Kathryn D., et al. "Long-wavelength reflecting filters found in the larval retinas of one mantis shrimp family (Nannosquillidae)." Current Biology 29.18 (2019): 3101-3108.

Hernáez, Patricio, et al. "Population demography and spatial distribution of the mantis shrimp Squilla biformis (Stomatopoda, Squillidae) from Pacific Costa Rica." Marine Ecology Progress Series 424 (2011): 157-168.

“Lysiosquillina maculata.” Wikipedia, 15 Oct. 2023, en.wikipedia.org/wiki/Lysiosquillina_maculata.

Marshall, N. J., M. F. Land, and T. W. Cronin. "Shrimps that pay attention: saccadic eye movements in stomatopod crustaceans." Philosophical Transactions of the Royal Society B: Biological Sciences 369.1636 (2014): 20130042.

Mazel, C. H., et al. "Fluorescent enhancement of signaling in a mantis shrimp." Science 303.5654 (2004): 51-51.

Patek, S. N., M. V. Rosario, and J. R. A. Taylor. "Comparative spring mechanics in mantis shrimp." Journal of Experimental Biology 216.7 (2013): 1317-1329.

“Peacock Mantis Shrimp.” Oceana, oceana.org/marine-life/peacock-mantis-shrimp/.

‌Schmidt, Amanda. “Peacock Mantis Shrimp Fact Sheet | Blog | Nature | PBS.” Nature, 20 Nov. 2023, www.pbs.org/wnet/nature/blog/peacock-mantis-shrimp-fact-sheet/.

Staaterman, E. R., et al. "Rumbling in the benthos: acoustic ecology of the California mantis shrimp Hemisquilla californiensis." Aquatic Biology 13.2 (2011): 97-105.

‌Thoen, Hanne H., et al. "A different form of color vision in mantis shrimp." Science 343.6169 (2014): 411-413.

Wikipedia Contributors. “Mantis Shrimp.” Wikipedia, Wikimedia Foundation, 12 Mar. 2019, en.wikipedia.org/wiki/Mantis_shrimp.