Wednesday, January 30, 2013

Origins of The Scorpion and The Frog and the Social Brain

Starting a weekly journalistic-type blog is a daunting task, especially for someone who is holding down other jobs (as most bloggers do). But I can't be happier that I started down this path in order to share with you all these wonderfully quirky stories of animal behavior and physiology. This week, I am happy to announce that The Scorpion and the Frog turns 1! It has been a remarkable first year: We've covered topics from whale dialects, to birds that kill their "siblings", to steroids and dominance in rodents; We've learned more about the researchers that contribute this fascinating knowledge to our global society; We've had fantastic guest posts by student guest writers; We've been recognized in other blogs and with awards; But my favorite aspect of this endeavor is that we are developing a growing community of readers and animal enthusiasts from all backgrounds. So today, I would like to reflect back on how we began a year ago with a repost of the very first The Scorpion and the Frog post, The Same Clay.

The Same Clay

According to a Hopi creation myth, the world was once nothing but water and dry land. The Sun, in his daily travels across the dry land, noticed that he had not seen a single living being. The Sun mentioned this observation to Hurúing Wuhti of the east and Hurúing Wuhti of the west, the deities of all hard substances, and they decided they would make a little bird. Hurúing Wuhti of the east made a wren out of clay and covered it with a piece of native cloth. The deities then sang a song over it and the wren came to life. They sent the wren to fly all over the earth to search for anything living, which it did. When the wren returned and reported that no living being existed anywhere, Hurúing Wuhti of the west shaped the clay to form all kinds of birds and placed these clay birds under the native cloth. The deities sang over the clay birds, bringing them to life, and they taught each of them what sounds they should make and sent them to populate the earth. Hurúing Wuhti of the west then shaped the clay to form all kinds of other animals and placed these clay animals under the native cloth. The deities sang over the clay animals, bringing them to life, and they taught them each what sounds they should make and sent them to populate the earth. Hurúing Wuhti of the east then shaped the clay to form a woman and a man and placed these people under the native cloth. The deities brought them to life with their song, and they taught them language and sent them to populate the earth.

I like this myth; in particular because it illustrates that despite the awesome diversity of the animals on our planet, we are all made of the same stuff and share many similarities. At first glance, we may be amazed by eels that resist eating prey fish who are providing a dental cleaning service (like the one on the left),

or by snakes that eat animals larger than their own heads and toads that save themselves from the jaws of death by puffing up their bodies even larger than the snake can handle (like the snake and toad battling it out on the right),

or by the elaborate displays of male birds in their attempts to woo females (like the golden pheasant below),

or by kangaroo moms that guard their toddler-like young in their own bodies (like the one on the right).

But at closer inspection, we realize that all of these animals are facing similar challenges: All animals are driven to eat and not be eaten, to stay healthy, to make babies, and to keep their babies alive. And animals have developed behavioral tools to achieve these goals, such as ways of finding or making food and a place to live, ways to defend these things, techniques for attracting the opposite sex, and parental methods. The details are extremely diverse across animal groups, but the ultimate goals and many of the strategies are common. And amazingly, the brain systems that regulate these behaviors are common too.

In a new synthesis of decades of research spanning the field of behavioral neuroscience, researchers Lauren O’Connell and Hans Hofmann from the University of Texas at Austin show that despite our impressive diversity, mammals, birds, reptiles, amphibians and fish are all molded from the same metaphorical clay. They specifically focus on two brain systems, often called the social behavior network and the mesolimbic reward system.

The social behavior network is a term first described in mammals by neuroscientist Sarah Newman to describe several brain regions that are all sensitive to steroid hormones (such as testosterone and estrogen), connect to each other, and are involved in many types of social behavior (including aggression, sexual behavior and parental behavior). We now know that reptiles, birds and fish also have brain areas that are similar in how they connect to one another and what neurotransmitters and other neurochemicals they use. More importantly, these brain areas seem to relate to the same types of social behaviors in similar ways.

The mesolimbic reward system is primarily a circuit of neurons that interact using the neurotransmitter dopamine. This neural circuit is central to how the brain controls motivation and a sense of desire and reward. This system is also involved in evaluating the importance of what is being perceived in order to behave accordingly. The mesolimbic reward system has been studied most in mammals, but birds, reptiles and fish are known to seek pleasure too and similar brain structures are likely involved.

This figure from O'Connell and Hofmann's paper in the Journal of Comparative Neurology shows corresponding brain regions in mammals, birds, reptiles, amphibians and fish. The images are shown as cross-sections of the brains as if we are looking directly at the front of the animals.
O’Connell and Hofmann show that the social behavior network and mesolimbic reward system work together as a single social decision-making system. For example, if one animal comes onto the territory of another animal, the brain areas of these two systems will work together to determine if the interloper should be fought, courted, nurtured, or eaten. (Imagine the consequences of getting this decision wrong!) Although mammals, birds, reptiles, amphibians and fish have very different lifestyles and brains, most of the brain areas of this social decision-making system are present, identifiable, and most importantly, play similar roles in regulating social behavior across all these animal groups. In the end, we’re not all so different after all.

Want to know more? Check these out:

1. O'Connell, L., & Hofmann, H. (2011). The Vertebrate mesolimbic reward system and social behavior network: A comparative synthesis The Journal of Comparative Neurology, 519 (18), 3599-3639 DOI: 10.1002/cne.22735

2. O’Connell, L., & Hofmann, H. (2011). Genes, hormones, and circuits: An integrative approach to study the evolution of social behavior Frontiers in Neuroendocrinology, 32 (3), 320-335 DOI: 10.1016/j.yfrne.2010.12.004

Wednesday, January 23, 2013

The Real Catfish of Lake Tanganyika

Photo of Manti Te'o by Shotgun Spratling
and Neon Tommy at Wikimedia
Poor Manti Te’o may just be the most gullible schlub on the planet. For those of you that haven’t heard the story, the Notre Dame linebacker and runner-up for the 2012 Heisman Trophy led his team to the BCS National Championship Game, despite (or perhaps inspired by) the tremendous personal losses he has suffered this season. Last September, Te’o learned first of the death of his grandmother, and then within hours learned of the death of his girlfriend, Lennay Kekua. But after months of grieving and playing his heart out, Te’o began to receive phone calls from his “dead” girlfriend, telling him she missed him. Totally freaky, right? Notre Dame hired investigators to look into the undead girlfriend and they discovered that not only is Kekua not dead, she was never alive. The girl never existed. And what of Te’o’s relationship with her? According to Te’o, he never actually met her in person: Their entire long-term relationship took place online and over the phone, so he never realized that her entire persona was a fraud. He was completely and totally catfished.

He was what?

The top definition of catfish at Urban Dictionary reads:

“A catfish is someone who pretends to be someone they're not using Facebook or other social media to create false identities, particularly to pursue deceptive online romances.

Did you hear how Dave got totally catfished last month?! The fox he thought he was talking to turned out to be a pervy guy from San Diego!”
The term apparently originates with the 2010 documentary, Catfish, about a young man who falls in love with a woman on Facebook… who turns out to be someone else. Ew. But why the term catfish? A story in the movie explains that when cod are shipped from North America to Asia, their inactivity can result in mushy meat. Fishermen discovered that putting catfish in the cod tanks will keep the cod active and preserve meat quality. Like catfish for cod, the guy philosophizes, people that have deceptive identities keep idle people active. (The producers of the documentary now produce an MTV series by the same name about this online phenomenon).

But it’s not like real catfish can imitate others… Or do they?

Three poisionous Lake
Tanganyikan catfish. Figure from
Jeremy's 2010 Evolution paper.
A 2010 paper by Jeremy Wright at the University of Michigan at Ann Arbor documents the first known case of mimicry in catfish. There are several types of mimicry in the animal world. In this case, Jeremy was investigating functional Müllerian mimicry, a phenomenon in which two or more poisonous species mimic each other's predator-deterring warning signals (as opposed to Batesian mimicry, where a non-poisonous animal looks like a poisonous one). It may seem excessive to have both poison and warning coloration, but poison only helps after you’ve been bit. If your predators are smart enough to learn from experience, you can benefit from having more poisonous buddies around that look just like you so that if a predator bites just one of you it will then learn to avoid all of you. Sometimes it pays to look just like everyone else.

But just because you look like everyone else doesn’t mean that it is because you’re imitating others. I mean, maybe that’s just the way you look. So how do you know if a bunch of animals that look like one another are using functional Müllerian mimicry?

Jeremy studied a number of similarly-colored, poisonous and closely-related catfish species in the African Great Lake, Lake Tanganyika. All of these Tanganyikan catfish species (from the Synodontis genus) have dark spots on a yellowish background and dark fins with white borders. Could this be because of functional Müllerian mimicry?

Jeremy put a bunch of largemouth bass each into their own tank. Largemouth bass are predators that use their vision to find and eat most any fish that will fit in their mouths. But these bass were from Michigan, so they’d never had any experience with a poisionous, spotted Synodontis catfish. A clear barrier divided each tank in half and the bass was placed on one side of the divider, and a bite-sized fish was put on the other. The bite-sized fish was either a spotted and poisonous Synodontis multipunctata catfish, a spotted and poisonous Synodontis petricola catfish, or a not-spotted and not-poisonous minnow. He then counted how many times the bass struck the plastic divider in 5 minutes as a measure of how much that bass wanted to eat the bite-sized fish. After the 5 minutes were up, Jeremy removed the divider and watched to see if the bass ate the bite-sized fish. For each bass, he did this every day for 5 days, giving each bass the same species of bite-sized fish every day, so it could learn from its past experiences.

A naïve largemouth bass excited to eat a bitesized, but poisonous Synodontis petricola catfish.

A naïve largemouth bass gets to try to eat a bitesized, but poisonous Synodontis petricola catfish… and it doesn’t go so well for him.

A no-longer naïve largemouth bass gives his best death stare to a bitesized, but poisonous Synodontis petricola catfish. Videos provided by Jeremy Wright.

On the first day with the bite-sized fish, all the bass struck at the divider equally regardless of whether it was a spotted poisonous catfish or a minnow. But after their first bite, the bass given spotted poisonous catfish quickly lost their interest in them even though the bass given minnows continued to vigorously strike at them every day. When Jeremy later gave them a different species of bite-sized fish, those previously given a spotted poisonous catfish avoided both species of spotted poisonous catfish, but readily ate the minnows. So the bass had learned. Spotted catfish: bad! Minnows: yum! And the spotted catfish look was transferable between the two species… the hallmark of functional Müllerian mimicry. Further analysis of the venom revealed that these catfish species were all equally poisonous: Painful, but not deadly.

Online catfish like Lennay Kekua are usually like these real-life spotted poisonous catfish: painful, but not (usually) deadly. And they typically have facebook pages and twitter accounts full of sexy photos and superficial chatter. If we’re smart, we can learn to avoid them. Do you know if all your “friends” on social media sites are who they say they are?

Want to know more? Check this out:

Wright, J. (2011). CONSERVATIVE COEVOLUTION OF MÜLLERIAN MIMICRY IN A GROUP OF RIFT LAKE CATFISH Evolution, 65 (2), 395-407 DOI: 10.1111/j.1558-5646.2010.01149.x

Wednesday, January 16, 2013

Science Beat

Sometimes science just makes more sense with a beat.

Fish Genetics:

Climate Science:

Sexy Reproduction:

Vote for your favorite in the comments section below. And if you feel so inspired, make a video of your own, upload it on YouTube and send me a link to include in a future battle!

Check out other sciency song battles at Scientist Swagger and Battle of The Grad Programs!

Wednesday, January 9, 2013

Animal Behavior in Science Fiction: Prey

I love a good science fiction story. The melding of quirky characters, exhilarating plots and scientific ideas is like whitewater kayaking for the brain. But as you stroll through the science fiction section of your local bookstore, you may notice the stark contrast between the plethora of books on space exploration, time travel, and robots; and the dearth of books on biological themes. That doesn’t make any sense to me, since biology is clearly the awesomest of all scientific disciplines. And stranger still is how few science fiction stories involve the science of animal behavior.

The first edition cover of Prey by
Michael Crichton shows his
fictitious swarm of nanoparticles.
Hence my joy in discovering books like Prey by Michael Crichton. Michael Crichton is arguably the preeminent (not to mention the most prolific) writer of biology-based science fiction, with stories we all recognize such as The Andromeda Strain and Jurassic Park. His books often combine the suspense, action and terror of a Hollywood blockbuster with the intellectual scientific understanding of a college biology course. He firmly roots his plots in scientific fact and then bravely makes a leap of reasoning into the unknown, leaving us all wondering, “What if that could happen?” Prey is no exception.

Prey is a cautionary tale of what could result when we mix powerful biological concepts, creative engineering, and corporate pressure. At the core of this story is a corporate laboratory in the Nevada desert that is engineering nanoparticles, microscopic robots that work as a swarm to achieve noble goals. Injected into a body, they can form themselves into a camera to send medical images to doctors to help diagnose patients with blocked arteries or weak heart valves. Released into war zones, they can organize themselves into the ultimate spy machines that cannot be shot down because any bullet would simply pass through the swarm. A brilliant concept – and based on accurate scientific facts and theories.

Crichton’s nanoparticles are built using nanotechnology, a science reliant on chemistry and biology in addition to engineering. As you read Prey, you learn these concepts as you follow the main character deeper into his perilous predicament. Each microscopic robot is harmless in and of itself – What makes them a threat is their group behavior.

A photo of a real flock of starlings. Photo by John Holmes at Wikimedia.
Nanoparticle behavior is determined by their computer programming, and lucky for us, the main character is a computer programmer who can explain all of the details of how their deadly behavior may have come to be. Their programming is based on distributed intelligence, a subfield of artificial intelligence in which each individual in a group has limited capacity for problem solving, but when they share with and respond to one another, the group can quickly develop effective solutions. Distributed intelligence is strongly based on the biology of group decision making in social animals, like ant colonies, bee swarms, fish schools, and bird flocks. The integration of the biology of predator-prey interactions into these systems makes them simultaneously more interesting and more terrifying. And what’s more, the swarm can learn and adapt to new situations based on ideas from quantitative genetics. By weaving together concepts from these disparate scientific fields, Crichton has imagined nanoparticles that individually are ultra-simple micro-machines. But together as a swarm, they are intelligent, they can learn, they can strategize… and they can kill.

A photo of a real swarm of bees. Photo by Micha L. Rieser at Wikimedia.
One of the most important aspects of what makes this book so terrifying is its plausibility. Although we have not yet created nanoparticles with these powerful abilities (that we, the lay public, are aware of anyway), we do have the scientific foundation for their creation. Crichton even provides scientific references in the back of the book if you want to learn more about the genetics, distributed intelligence, or nanotechnology concepts he drew on for his fictitious novel. But as careful as he was in his accurate use of science to set up the plot and much of the story, the conclusion is where Crichton’s science becomes an obvious work of fiction.

Without going into too much detail, the final scenes fall apart on the plausibility factor. In order to avoid spoiling the end for those of you who wish to read it (and you should), I won’t say how, but some of the biological events just could not have happened as he described. And Crichton should have known better – he had a medical degree from Harvard for Pete’s sake! But when push comes to shove, sometimes accurate scientific principles move too slowly for the action-packed pace of a best-seller.

A photo of a real school of bigeye scad. Photo by Steve D. at Wikimedia.
In science fiction, does good fiction always have to be at the expense of good science? Even in science writing, which conveys complex scientific concepts to the public, scientific details are often stretched or overlooked in an attempt to make the overarching concept more interesting and comprehensible to as many readers as possible (although this is an issue for another post altogether). My point is, people are naturally curious about science, which aims to provide understanding of how everything works. But understanding lies in the details, and details can be tedious and confusing and don’t always fit the timeline of the plot or make the most exciting climax. There is a push and pull between accurate science and good storytelling. But I don’t think they are mutually exclusive… I think we can have it all.

In the end, Prey is a fantastic story and Michael Crichton does an excellent job incorporating and explaining current scientific ideas and how their application may lead to leaps in medical advances or to horrific scenarios of death and destruction. I highly recommend it to anyone willing to overlook a biological detail or two in the name of excitement and intrigue. But my search for the perfect biology-centric science fiction book continues.

Do you have a favorite science fiction book that incorporates animal behavior? Share it with us in the comments below!

Wednesday, January 2, 2013

When The Going Gets Tough, The Tough Become Babies

We celebrate the New Year as a time of rebirth, renewal, and do-overs. We join gyms, swear off our bad habits, and promise to be better people. This is especially true for those of us that have had a rough 2012… Our 2013-version-of-us has got to be better, right? But what if you could get a real do-over? What if you could be a kid again, grow up again, and become a brand new person? As far-fetched as it may sound, some animals do exactly that.

Cnidarians (the “C” is silent) are a huge group of aquatic animals that includes jellyfish, corals, and anemones (like the one Nemo lived in – Yeah, that tentacled home was a living animal). They are named after prickly plants known as nettles, or cnides in Greek, and if you touch one you will quickly know why. Cnidarians, armed with stinging cells called nematocysts, sting at the slightest touch.

Jellyfish make up many of the cnidarian species, and they have been found in every ocean and at every depth. Some even live in freshwater. The “typical” jellyfish life cycle starts when eggs and sperm are released into the water and find one another. When they do, they form larvae, which you can think of as baby jellyfish. The larvae sink and settle on a hard surface, where they mature into polyps. These polyps are jellyfish in a juvenile stage. The polyps elongate and begin to bud off adult medusa, which are the bell-shaped blobs with tentacles that most of us think of when we think of a jellyfish. Medusa mature to become reproductive adult jellyfish.

The jellyfish life cycle by Zina Deretsky at the National Science Foundation (NSF). Image available at Wikimedia.
Larval and polyp jellyfish are much more resistant to harsh conditions then are medusa jellyfish. When life gets hard for a jellyfish, perhaps because of starvation, physical damage, temperature changes or salinity changes, those that are in the larval or polyp stages can often shrink and rest in a hibernation-like state while they wait for more favorable conditions. But in some species, young adult medusa can even regress back to the juvenile polyp stage. By reverting back to a juvenile stage, they have more protection from the challenging world around them.

In most cases, this reversal to a juvenile state can only happen in young medusa that have not yet developed their gonads. Thus, the onset of sexual reproduction (puberty, if you will) might be regarded as the point of no return in development. However, one species, called the immortal jellyfish, has shown that this rule can be broken.

As an adult medusa, the immortal jellyfish is a pea-sized jellyfish with a round bell, bright red stomach and anywhere from 8 to 90 tentacles. It is currently the only known animal that can regress from a fully reproductively mature adult into a juvenile polyp. If exposed to dangerous conditions, immortal jellyfish medusae completely reduce all of their medusa-specific organs and tissues and develop new polyp-specific tissues, essentially becoming kids again!

This figure from the Piraino et al. 2004 paper at the Canadian Journal of Zoology shows the life stages of the immortal jellyfish. The adult medusa is in panel (a). Panels (b) and (c) show the medusa tranforming to a ball-like blob as it reverts to a juvenile stage. The green stain in these panels shows the cells initiating this transformation. Panel (d) shows the remnant of a medussa, and the black arrow shows the stalk that is common in the polyp stage. Panel (e) shows the resulting juvenile polyp.
But wait! It gets better! Theoretically, if an animal can revert to a juvenile stage at any point in its adult life, it could attain immortality. But if that were true, they would have the classic immortality problem: These animals would reach such high populations they would saturate the world’s oceans…And this may actually be happening.

Immortal jellyfish are thought to originally be from the Caribbean, but they have since been discovered worldwide and their populations seem to be growing. Likely, they are hitching rides in the ballast water that is sucked into cargo ships to provide stability. If this is true, the immortal jellyfish polyps could be attaching to the ships’ hulls and settling in for a long voyage to a new home.

We don’t yet know if the immortal jellyfish are actually immortal, but it is fun to consider that they might be (although they can still be killed by predators or viruses, so they’re not invincible). And we can take inspiration from them: When the going gets tough, try reverting to your more resilient juvenile self, but be thankful you don’t have to go through middle school again!

Happy New Year!

Want to know more? Check these out:

1. Piraino, S., De Vito, D., Schmich, J., Bouillon, J., & Boero, F. (2004). Reverse development in Cnidaria Canadian Journal of Zoology, 82 (11), 1748-1754 DOI: 10.1139/z04-174

2. Miglietta, M., & Lessios, H. (2008). A silent invasion Biological Invasions, 11 (4), 825-834 DOI: 10.1007/s10530-008-9296-0