Have you heard about Mantis Shrimp?
Have you heard about Mantis Shrimp? Stomatopods? These aggressive little crustaceans found across the Pacific and Indian Oceans are an absolute hot spot for interesting facts. These intriguing creatures are so unique that they are even being modelled for the creation of armour technologies, but I will get back to that later.
There are over 450 known species of Mantis Shrimp, each with their own specific adaptions to their habitats, from “spearers” to “hammerers” (Patek et.al., 2013) and even down to the way their eyes filter light. Particularly interestingly, Mantis Shrimp have up to 16 types of photoreceptors in their eyes (Bok et.al., 2014; Cronin et.al., 2014). Photoreceptors are the functional parts of the eye responsible for detecting and responding to light signals, humans have types of photoreceptors; red light cones (~560nm), green light cones (~530nm), blue light cones (~420nm) and rods (~510nm and capable of detecting light at very low levels). Upon hearing that Mantis Shrimp have such a large number of photoreceptors, many jump to the conclusion that there are colours that Mantis Shrimp can see that we as humans cannot… this is only half true.
Firstly, Mantis Shrimp can indeed see some things which we humans cannot, and this is due to their ability to detect Ultraviolet light and circularly polarised light (Chiou and Wang, 2020). In fact, Mantis Shrimp are currently the only known animals that possess both circular and linear polarisation vision. Mantis Shrimp are capable of converting circularly polarised light into linearly polarised light through wave retardation so that the signals can be processed through the linear polarised light channels. Furthermore, at least three photoreceptors are sensitive to ultraviolet light (Marshall and Oberwinkler, 1999) between ~315-380nm.
Sadly, or happily for those not wanting to miss out on colours we can’t see, Mantis Shrimp are not getting more colours than we are in the visible light spectrum. In reality, the opposite may be true. Mantis Shrimp have a multitude more photoreceptors than we humans do, however each photoreceptor is much more narrowly sensitive with at least 12 colour channels (Thoen et.al., 2014). Unlike humans, Mantis Shrimp are unable to “blend” light into more colours. Humans are able to determine how much light is being detected by each cone in order to determine where on the colour spectrum the light we receive lies, whereas Mantis Shrimp can only perceive each colour represented in their photoreceptors and not any colours in between.
Even more amazingly, Mantis Shrimp are able to differentially filter light entering their eye depending on which depths they live at and how much light is available there (Cronin et.al., 2001). Their eyes are also able to independently move in three different directions; left to right, up and down, and backwards and forwards (Land et.al., 1990). That’s enough about their eyes, I promised to tell you about how Mantis Shrimp are helping to develop armour.
These feisty crustaceans have the nickname of “thumb splitter” due to the impressive feeding appendages which can pack a powerful punch and cut through a finger to the bone if handled inaccurately. As discussed by Patek et.al. (2004) these appendages can be sharp and spear-like or more blunt and hammer-like. The force that is exhibited by Mantis Shrimp through these weapons is unparalleled, reaching up to 1000N at 20m/s, enough to cause the surrounding water to reach temperatures found on the surface of the sun. The important question that these facts highlight – how can they produce these forces without their own bodies breaking?
Taylor and Patek (2010) endeavoured to answer this question, starting with their Telson. This abdominal armour acts as an inelastic punching bag and is able to dissipate impact force (Taylor et.al., 2019). Grunenfelder et.al. (2014) observed these properties and have been experimenting with creating artificial materials with similar properties with looks for engineering and armour. As always, there is so much more I could tell you, but then I’d be taking away all of your fun looking up how they can detect cancer and whether they are living dinosaurs.
References
Bok, M.J., Porter, M.L., Place, A.R. and Cronin, T.W., 2014. Biological sunscreens tune polychromatic ultraviolet vision in mantis shrimp. Current Biology, 24(14), pp.1636-1642.
Chiou, T.H. and Wang, C.W., 2020. Neural processing of linearly and circularly polarized light signal in a mantis shrimp Haptosquilla pulchella. Journal of Experimental Biology, 223(22).
Cronin, T.W., Bok, M.J., Marshall, N.J. and Caldwell, R.L., 2014. Filtering and polychromatic vision in mantis shrimps: themes in visible and ultraviolet vision. Philosophical Transactions of the Royal Society B: Biological Sciences, 369(1636), p.20130032.
Cronin, T.W., Caldwell, R.L. and Marshall, J., 2001. Tunable colour vision in a mantis shrimp. Nature, 411(6837), pp.547-548.
Grunenfelder, L.K., Suksangpanya, N., Salinas, C., Milliron, G., Yaraghi, N., Herrera, S., Evans-Lutterodt, K., Nutt, S.R., Zavattieri, P. and Kisailus, D., 2014. Bio-inspired impact-resistant composites. Acta biomaterialia, 10(9), pp.3997-4008.
Land, M.F., Marshall, J.N., Brownless, D. and Cronin, T.W., 1990. The eye-movements of the mantis shrimp Odontodactylus scyllarus (Crustacea: Stomatopoda). Journal of Comparative Physiology A, 167(2), pp.155-166.
Marshall, J. and Oberwinkler, J., 1999. The colourful world of the mantis shrimp. Nature, 401(6756), pp.873-874.
Patek, S.N., Korff, W.L. and Caldwell, R.L., 2004. Deadly strike mechanism of a mantis shrimp. Nature, 428(6985), pp.819-820.
Patek, S.N., Rosario, M.V. and Taylor, J.R.A., 2013. Comparative spring mechanics in mantis shrimp. Journal of Experimental Biology, 216(7), pp.1317-1329.
Taylor, J.R., Scott, N.I. and Rouse, G.W., 2019. Evolution of mantis shrimp telson armour and its role in ritualized fighting. Journal of the Royal Society Interface, 16(157), p.20190203.
Taylor, J.R.A. and Patek, S.N., 2010. Ritualized fighting and biological armor: the impact mechanics of the mantis shrimp's telson. Journal of Experimental Biology, 213(20), pp.3496-3504.
Thoen, H.H., How, M.J., Chiou, T.H. and Marshall, J., 2014. A different form of color vision in mantis shrimp. Science, 343(6169), pp.411-413.
Fiction and Poetry
Written by Libby Bowles
I’m a PhD Researcher at Prifysgol Aberystwyth, studying the perenniality syndrome in Grasses. I’m passionate about public engagement in science and the sharing of knowledge regarding the world we live in, especially the weird and wonderful.