The Mantis Shrimp: Supervillain of the Sea

These amazing creatures, also known as stomatopods, dwell in shallow near-shore marine environments. Most are around 15 cm in size, though some can grow up to 40 cm long, which is longer than my forearm. They aren’t true shrimp (which are classified in Order Decapoda, not Stomatopoda), though both are crustaceans within Class Malacostraca. Mantis shrimp possess some unique abilities, which are sharpened by their violent, aggressive temperaments, making them the crustacean supervillains of the oceans.

“Odontodactylus Scyllarus 2” by Roy L. Caldwell, Department of Integrative Biology, University of California, Berkeley, via Wikimedia Commons

So what are their superpowers?

  • Amazing Vision. Animals perceive color by absorbing various wavelengths of light with color photoreceptors, each type absorbing best at specific wavelengths. In humans, the “blue,” “green,” and “red” photoreceptors (which actually have peak absorptions in the blue, green, and yellow ranges, respectively) allow us to see colors ranging from red to violet. Most birds have a fourth type of color photoreceptor that is sensitive to UV wavelengths, allowing birds to see ultraviolet as a color.

    Mantis shrimp? They have up to sixteen types of photoreceptors. Twelve of them are for color.

    Four of these photoreceptors are for ultraviolet alone, and mantis shrimp color vision ranges from red to ultraviolet. But this incredible level of color detail, which allows them to see hues we humans cannot even imagine, is not the only amazing thing about mantis shrimp vision.

    Mantis shrimp can “tune” their vision based on environmental light conditions. Underwater, longer wavelength light tends to fade away faster than shorter wavelength light. This means that in very shallow water, the full spectrum of light is visible, but in deeper water, the environment is composed of shades of blue, violet, and ultraviolet. Mantis shrimp have color filters in their eyes that allow them to adjust to changes in the wavelength composition of their environment.

    “Mantis shrimp near Nusa Kode Island,” by Alexander Vasenin, via Wikimedia Commons

    Each eye is divided into two hemispheres, with an “equator” of six lines of ommatidia. Each line analyzes a different aspect of incoming visual information. The visual fields of the top and bottom sections of each eye overlap to some degree, allowing the mantis shrimp to have stereoscopic vision within a single eye, which is useful, since the two eyes move independently of each other. Mantis shrimp vision is so complex that different sections of the mantis shrimp’s compound eyes are allotted separate tasks. Using one part of the eye, a mantis shrimp might observe the color of an object; using another part, it might analyze the polarization of incoming light. Our own visual system cannot detect the polarization of light, but mantis shrimp can glean useful information about the orientation and texture of objects that reflect and scatter light in various directions.

    If their vision is so complicated, you might ask, how do mantis shrimp process all of the information, given the small size of their brains? As it happens, mantis shrimp employ parallel processing within the retina itself, meaning that much of their visual intake is processed before it even reaches their brain.

  • Mantis shrimp vision enables them to see in ultraviolet, to perceive fantastic color detail, and to detect polarized light – an impressive array of abilities. What other powers do they have in their arsenal?

  • Incredible Punch. As predators, mantis shrimp pursue one of two strategies of attack: spearing and smashing. Many species of mantis shrimp are “spearers,” killing their prey (and, frequently, each other) by stabbing with specialized sharp limbs. As impressive as this is, I find the “smashers” even more amazing.

    For an example of a “smasher,” let’s look at the peacock mantis shrimp, Odontodactylus scyllarus*:

    “Odontodactylus Scyllarus” by Silke Baron, via Wikimedia Commons

    The peacock mantis shrimp has a pair of reinforced, club-shaped limbs specialized for punching, rather like a pair of boxing gloves permanently attached to their bodies. The mantis shrimp prepares for a punch by locking the club in place with a spring-and-latch mechanism, then building up tension against the latch by contracting a muscle, before releasing the latch all at once. The club shoots forward at speeds up to 23 meters per second (that’s about the speed of a running cheetah) and punches the mantis shrimp’s prey with a force of up to 1500 Newtons. The punch only takes a few milliseconds, and the acceleration of the club can equal that of a .22 caliber bullet.

    Such a punch can be devastating, even to strong materials like a clam’s shell, but the attack isn’t over yet. The club punches through the water so fast that surrounding water vaporizes in a process called cavitation, creating a pocket of empty air in the wake of the punch. This space doesn’t stay empty for long. The surrounding water collapses back in on the space and crashes into the mantis shrimp’s prey in a second onslaught, often even more powerful than the first.

    A “smasher” mantis shrimp doesn’t let up the beating until its prey – a crab, a snail, a clam, or even a fellow mantis shrimp – shatters. Their punches are so powerful they can even crack aquarium glass, which make them a fearsome enemy indeed.

  • Body Armor. “Smasher” mantis shrimp can repeatedly pound away at their enemies with enough force to shatter shells, yet they only need to replace their clubs with the occasional molt. How can this be?

    It turns out that the molecular makeup of mantis shrimp exoskeletons – particularly of their clubs – is exceptional. On a micro scale, the structure of the club is extraordinarily resistant to fracture and damage, yet retains its hardness and effectiveness as a weapon. The mantis shrimp’s stiff telson – the hindmost segment of the exoskeleton – also excels at dissipating violent impacts, which mantis shrimp encounter during their frequent bouts of violence against one another.

    Like the resilient, resourceful villains they are, mantis shrimp employ reinforced armor both as protection and as a weapon.

  • Captivating Beauty. On top of these abilities, many mantis shrimp are simply breathtaking to look at – after all, every worthwhile villain needs a good sense of style. A picture will tell more than words alone, so feast your eyes on the glorious mantis shrimp:

    “Odontodactylus scyllarus 1” by Jens Petersen, via Wikimedia Commons

    Not all mantis shrimp are so brightly colored, but some – like the peacock mantis shrimp – are decked out in every color of the rainbow (and perhaps a few that only mantis shrimp can see).

  • Evil Disposition. All these powers packed into one creature might qualify mantis shrimp for membership in the Justice League, but they are no heroes. Behind the rainbow exterior, the exceptional vision, and the intimidating strength, lies the heart of a violent, ruthless predator.

    Mantis shrimp are merciless in their attacks on helpless prey, and they don’t limit their violence to obtaining food. Some species attack each other in ritualized displays of violence, assessing the strength of their rivals by punching them on the telson. This habit of violence toward each other is another reason mantis shrimp need such resilient armor.

The inescapable conclusion? Mantis shrimp possess exceptional vision, proficiency in violence, and strong defense. They are creatures of breathtaking beauty and bloodthirsty temperament. They are true supervillains.

“Mantis shrimp from front” by Jenny, via Wikimedia Commons

What other creatures do you think deserve to be called the supervillains (or superheroes) of the animal kingdom? Leave your suggestions in the comments!

*Odontodactylus scyllarus roughly translates to “tooth-finger Scylla,” an appropriately monstrous name for a mantis shrimp.


Cronin, Thomas W., Roy L. Caldwell, and Justin Marshall. “Sensory adaptation: tunable colour vision in a mantis shrimp.” Nature 411, no. 6837 (2001): 547-548.
Cronin, Thomas W., and Justin Marshall. “Parallel processing and image analysis in the eyes of mantis shrimps.” The Biological Bulletin 200, no. 2 (2001): 177-183.
Cronin, Thomas W., N. Justin Marshall, Carole A. Quinn, and Christina A. King. “Ultraviolet photoreception in mantis shrimp.” Vision research 34, no. 11 (1994): 1443-1452.
Dingle, Hugh, and Roy L. Caldwell. “Ecology and morphology of feeding and agonistic behavior in mudflat stomatopods (Squillidae).” The Biological Bulletin 155, no. 1 (1978): 134-149.
Patek, S. N., and R. L. Caldwell. “Extreme impact and cavitation forces of a biological hammer: strike forces of the peacock mantis shrimp Odontodactylus scyllarus.” Journal of Experimental Biology 208, no. 19 (2005): 3655-3664.
Patek, S. N., W. L. Korff, and R. L. Caldwell. “Biomechanics: deadly strike mechanism of a mantis shrimp.” Nature 428, no. 6985 (2004): 819-820.
Taylor, J. R. A., and S. N. Patek. “Ritualized fighting and biological armor: the impact mechanics of the mantis shrimp’s telson.” The Journal of Experimental Biology 213, no. 20 (2010): 3496-3504.
Weaver, James C., Garrett W. Milliron, Ali Miserez, Kenneth Evans-Lutterodt, Steven Herrera, Isaias Gallana, William J. Mershon et al. “The stomatopod dactyl club: a formidable damage-tolerant biological hammer.” Science 336, no. 6086 (2012): 1275-1280.
Nathans, Jeremy, Darcy Thomas, and David S. Hogness. “Molecular genetics of human color vision: the genes encoding blue, green, and red pigments.” Science 232, no. 4747 (1986): 193-202.

See also:

Webcomic on mantis shrimp, by The Oatmeal.
Radiolab podcast on color, including a discussion on mantis shrimp vision and an full choir illustrating mantis shrimp vision through sound.

Book Look: Quiet, by Susan Cain

Quiet: The Power of Introverts in a World That Can’t Stop Talking is a recent book by introvert and professional negotiator Susan Cain. The essential message is simple: Western (particularly American) culture prizes extroversion, but introverts make up one-third to one-half of the population, and their contributions are just as important.

Cain starts out by explaining some basic personality theory and exploring the roles of introverts and extroverts in society. During the past century, she states, the “mighty likeable fellow” has emerged as the American ideal, particularly in the business world. At the same time, collaborative group work and open office plans have become the status quo in many work environments, despite evidence that they may not actually improve productivity. Introverts in particular often work best in quiet solitude – although, as Cain emphasizes, introversion is not the same thing as unsociability. Introverts love socializing just as much as any human does, but we gravitate towards different situations. Often, we might avoid a crowd in favor of an evening with a few close friends.

In the next section, Cain explores the psychology and biology behind introversion. Some research indicates that introverts may be more sensitive to external stimuli, even as very young children. In one study, researcher Jerome Kagan exposed four-month-old babies to stimuli like loud noises, bright colors, and strong smells, and observed their reactions. He then tracked these children as they grew up. The children who reacted more strongly to the stimuli (exhibiting behaviors like crying or getting upset) tended to grow into quieter, more introverted teenagers. On the other hand, children who were unfazed by stimuli tended to develop extroverted personalities when they grew older. These findings suggest a “sensitivity” model to explain introversion/extroversion: introverts are easily overwhelmed by too many stimuli, but less likely to get bored or restless in a quiet environment. Thus, a highly sensitive, introverted person is uncomfortable at a loud party, but perfectly content to curl up with a book at home, while a highly extroverted person grows restless sitting alone at home, and craves the stimulation of a loud party.

This isn’t the only model of introversion/extroversion that Cain explores. Genes, among other factors, play a role in personality. Cain argues that culture and upbringing are particularly influential in introversion and extroversion, particularly on a societal scale. Many Asian cultures, for instance, place a comparatively higher value on quiet, introspection, and caution – that is, introverted traits. Cain contrasted this to the United States and other Western cultures, which she believes overemphasize the gregarious, enthusiastic extrovert ideal at the expense of recognizing the value of introverts.

Occasionally, Cain seems uncomfortably close to arguing that introverts are not only equal, but superior to extroverts. Introverts, we are told, tend to have greater powers of single-minded concentration, more sensitivity to detail, better impulse control, and more persistence. Borrowing a metaphor from science writer David Dobbs, Cain compares introverts to orchids. As Cain describes it, we introverts are delicate and “wilt easily,” but bloom with extraordinary beauty in the right conditions. Extroverts, on the other hand, are dandelions – hardier, but less exceptional. To be fair, Cain is explicit that introverts and extroverts are equally intelligent and have equal value, so perhaps her apparent favoring of introversion over extroversion is a reaction against a culture that tends to value the opposite.

Similarly, Cain recognizes that introverts come in all shapes and colors, but she spends an inordinate amount of time discussing a few select traits. For example, shyness is a stereotypical introvert trait, but nowhere near universal in reality; it comes up again and again in the book. Personally, I would have liked to learn more about the psychology and biology of introversion, although the speculation on its societal merits and disadvantages is also interesting.

The final section of the book steers from psychology toward self-help. Quiet is definitely aimed at an introverted audience, although there are some nods toward extroverted readers, particularly those who have close relationships with introverts. How, Cain probes, can an introvert thrive in an extrovert’s world? Do introverts have to deny their personalities to achieve success? How can we encourage introverted children in a society where extroversion is the ideal? One strategy is the use of “free traits” – adopting aspects of a different persona when one’s own personality traits are insufficient. For instance, Cain relates the story of an introverted professor who adopts an extroverted attitude in order to teach effectively. Incorporating extroverted “free traits” into one’s personality can be useful, but the effort is mentally exhausting. Nevertheless, Cain argues, it is sometimes worthwhile to act out of character for the sake of accomplishing a rewarding task.

I have mixed feelings about Quiet. I’m an introvert myself, but I was uncomfortable with the occasional implication that introversion is superior to extroversion. At the same time, I enjoyed the analysis of what introverted personalities can contribute in a society where people are expected to be outgoing. I like learning the science behind human behavior, and the psychology of introversion and personality theory is certainly interesting. Quiet has a few flaws, but I’m glad I read it. It got me thinking about the mistake of idealizing one default personality type when, in reality, it is our mixture of types and talents that helps us succeed.

Cain, Susan. Quiet: The Power of Introverts in a World That Can’t Stop Talking. New York: Crown Publishers, 2012.

What are your experiences regarding introversion and extroversion in society? Do you agree that Western culture idealizes extroverted personality traits? Leave your thoughts in the comments!

Book Look: The Seven Sins of Memory

Memory is a funny thing. There are times when an important errand slips my mind, but I can’t get that one song out of my head. Distant memories fade with time, but some experiences can haunt people for years. Strangest of all, people can – and frequently do – develop memories of things that never happened at all.

These various peculiarities are the focus of The Seven Sins of Memory: How the Mind Forgets and Remembers. Harvard psychology professor Daniel L. Schacter takes the reader through what he classifies as the seven “sins” of memory. What are these sins? What troubles do they cause us? Could these sins help as well as hurt?

Sin 1: Transience. “Hmmm, that was a while ago, and my memory is a little vague…”

Memories fade as time passes. Recent events stand out sharply in our minds, but details become hazy after a few hours or days pass by. Schacter argues that the memory system tends to forget old information because more recent information – such as where you parked your car this morning, or where you found your last meal – is more likely to be important. From an evolutionary standpoint, it makes little sense for our memories to retain useless information.

Sin 2: Absent-mindedness. “Now where did I put my keys? They were in my hand a moment ago…”

Things slip our minds all the time. The brain can’t focus on too many things at once, so we relegate our attention to the present task, and sometimes end up forgetting things we wanted to do in the future. As any maker of to-do lists knows, the best way to avoid absent-mindedness is to leave reminders to jog our memories at a later time. However, this isn’t as helpful with other types of absent-mindedness, such as when a momentary distraction prevents important information from being encoded in our memories in the first place. For instance, if I’m absorbed in thinking about that to-do list as I walk through the front door, I might never notice where I put the keys.

Sin 3: Blocking. “Oh, what’s that word? It’s on the tip of my tongue!”

We’re all familiar with the maddening sensation of knowing a fact, only to find it just out of reach when we need it. Interestingly, a number of different languages use the phrase “on the tip of the tongue” or similar; the sensation is familiar to people all over the world. Schacter argues that this type of blocking occurs when our mental link between the concept and the word is too tenuous, particularly when we haven’t used the information for a while. More perniciously, blocking can also take the form of repression and even amnesia, when people try to cope with unwanted memories by pushing them away.

Sin 4: Misattribution. “I love J.K. Rowling – The Hunger Games is my favorite series!”

Surprisingly often, people confuse or conflate one entity with another in their recollections. They mix up two people, misremember the context of an event, or forget the source of a piece of information. Misattribution is partly why eyewitness testimony is terribly unreliable. Witnesses might remember a suspect, but mistake when they saw him, where, and what he was doing; this can lead to serious errors, like accusing an innocent bystander of a crime.

Sin 5: Suggestibility. “Brown hair? I don’t think so. Well, maybe. I think he might have … yes, his hair was definitely brown!”

Outside influence can also influence how we remember events, which is another reason not to implicitly trust eyewitness testimony. The slightest leading question can alter what a person remembers, even if the person recognizes it as a false suggestion. People may vividly remember something that is false – even though they previously stated that it never happened.

Sin 6: Bias. “I knew it all along.”

We view the past through the lens of our current knowledge and feelings. Hindsight, as the saying goes, is 20/20, and if we know the outcome of an event, we think it should have been obvious beforehand. In general, we tend to remember our past selves as more similar to our current selves than we actually were; sometimes, however, people mentally exaggerate how unhappy they used to be, making themselves feel more content by comparison.

Sin 7: Persistence. “I can’t get it out of my head!”

Some memories are less subject than usual to the sin of transience, and some experiences will not fade away despite a strong desire to forget. This can range from the benign (can’t get that song out of your head?) to the debilitating (such as PTSD), but unsurprisingly, highly emotional memories tend to be the most persistent.

The sins of memory run the gamut from annoying and commonplace to serious and even ruinous. And yet, at the end of the book, Schacter argues that these qualities are virtues in disguise.

Schacter contends that all of these memory problems – troublesome though they can be – are aspects or byproducts of a memory system that evolved to be efficient. On the whole, humans excel at calling to mind the facts we need, while ignoring those we don’t. What would be the use of devoting energy to forever remember information that we will almost certainly never use again? How could we function if we could not distinguish relevant from irrelevant? We don’t always appreciate it, but our memories serve us well much more often than they let us down.

The Seven Sins of Memory is an interesting exploration of the quirks of memory. Schacter discusses the troubling failures of our memory, and demonstrates that the qualities we think of as flaws are integral to the function of an efficient, powerful system shaped by natural selection.

But I still reserve the right to be annoyed when, for the life of me, I can’t remember where I put my keys.

Schacter, Daniel L. The Seven Sins of Memory: How the Mind Forgets and Remembers.” Boston: Houghton Mifflin Company (2001).

Book Review: Carcharinus obscurus

I’ve written a couple of reviews of popular science books by celebrated science writers, but today I’m reviewing something a little different, and a little more … obscure.

Carcharinus obscurus is the first in a series of books by Zachary Webb Nicholls, also known as “Dr. Jaws,” who is an author, artist, and student at my alma mater, the College of William and Mary. Dr. Jaws plans to focus on a different species of shark in each book in the series, starting with the Dusky Shark, Carcharinus obscurus. Why the Dusky Shark? In an interview, Dr. Jaws said that this species deserves particular attention because “it’s not doing so well, conservation-wise.”

This book is, in a word, unique. It blends art, science, and mythology into a slightly surreal celebration of the Dusky Shark. Dr. Jaws incorporates the shark as an animal and as a cultural icon, but unlike many popular science books, Carcharinus obscurus doesn’t really have an encompassing narrative or message (other than, perhaps, “sharks are amazing, and you should learn more about them.”) The structure of the book could be summed up in a quote from Dr. Jaws: “One day, I started a poem and liked it, and went from there.” In my opinion, it doesn’t need a strict narrative.

Carcharinus obscurus is a very quick read. It weighs in at less than 50 pages, of which pictures and poetry take up a large chunk. The first half of the book drifts from poetry extolling the wonders of Domain Eukarya to drawings and photographs of sharks, inserting keyword ciphers and shark-related factoids along the way. My favorite section of the book is the last one. In the final 20 pages, Dr. Jaws uses a story about a leatherback and a shark-goddess to convey a sense of wonder and reverence toward sharks.

I wanted to create something distinct, something that stands out and grabs attention, because sharks are just so charismatic, and so many people have done something on them… To me, sharks are like living poetry. I naturally have just a strange sense of awe for them. – Dr. Jaws, in an interview

If you are interested in marine life and are searching for something low-key and a little different to peruse, take a look at Carcharinus obscurus.

I drew a picture based on "Sea of Sauda," the final story in Carcharinus obscurus. I liked the mood of the story, and wanted to draw my own take on it.

I drew a picture based on “Sea of Sauda,” the final story in Carcharinus obscurus. I liked the mood of the story, and wanted to draw my own take on it.

Dr. Jaws’ Facebook Page
Author’s Page at Deep Sea Publishing
Book Trailer on YouTube
Carcharinus obscurus is available for purchase at

Unlocking Pandora’s Virus

By most standards, viruses aren’t alive. They have genetic material, yes, and they reproduce, but a true living organism must have some form of metabolism – it must be able to build up and break down chemicals on its own. Viruses have no metabolism. They don’t make their own proteins, and they can only reproduce by enslaving host cells into manufacturing copies of themselves, and then forcing the host cell to self-destruct and unleash the new viruses. However, researchers Nadége Philippe and colleagues have recently discovered massive, bacteria-sized viruses with genomes larger than those of any viruses known heretofore, and this discovery could change our understanding not only of viruses, but of the tree of life.

These newly discovered viruses are the largest found to date, but they are not the first giant viruses ever found. A decade ago, researchers Bernard La Scola and colleagues discovered the Mimivirus, which has a genome of 1.18 million bases. Since then, researchers have found similar “megaviruses,” which seem to share certain structural and functional peculiarities. Now, Philippe and colleagues have found two huge viruses, so very unique that they have been dubbed the “Pandoraviruses.”

“It’s like finding a sasquatch.” – Elodie Ghedin, virologist at University of Pittsburg, PA1

Pandoravirus salinus and Pandoravirus dulcis weigh in at 2.47 and 1.91 million base pairs long, respectively, and P. salinus is 1 micron long – one hundred times the size of most viruses! So, if these viruses are so large, why haven’t researchers seen them before now? Actually, they may have done so unknowingly. The discoverers suspect that people have seen Pandoraviruses before, but assumed that they were bacteria, since they were much larger than any known viruses. In fact, Pandoraviruses may be quite common – the researchers found one in Chile and one in Australia, and they could well exist in many other places.

Pandoraviruses are viruses, without a doubt: they do not produce their own proteins, they depend on living cells for replication, and they share some genes with other large viruses. Morphologically and genetically, however, Pandoraviruses are unique. Unlike most large viruses, they require activities in the host cell’s nucleus, lack many core viral genes, and have relatively few introns (pieces of a gene that are spliced out of the final gene product) in their genomes.

As the researchers stated in their paper, “93% of Pandoraviruses genes resemble nothing known, [and] their origin cannot be traced back to any known cellular lineage.”2 Their almost alien genome, coupled with the huge size of the genome, may even suggest the existence of a fourth domain of life, in addition to Bacteria, Archaea, and Eukaryota. Perhaps, the researchers suggest, early life was extraordinarily diverse, consisting of many different domains that evolved, existed, and eventually died out, leaving only the three that we know today – and maybe a fourth that we are just on the frontier of discovering.


1Pennisi, Elizabeth. “Ever-Bigger Viruses Shake Tree of Life.” Science Vol. 341, Issue 6143, pp. 226-227 (2013). DOI: 10.1126/science.341.6143.226.

2Philippe, Nadége, Matthieu Legendre, Gabriel Doutre, Yohann Couté, Olivier Poirot, Magali Lescot, Defne Arslan, Virginie Seltzer, Lionel Bertaux, Christophe Bruley, Jérome Garin, Jean-Michel Claverie, Chantal Abergel. “Pandoraviruses: Amoeba Viruses with Genomes Up to 2.5 Mb Reaching That of Parasitic Eukaryotes.” Science Vol. 341, Issue 6143, pp. 281-286 (2013). DOI: 10.1126/science.1239181.