how to ruin your crustacean karma

A few weeks ago, a local Alaskan was kind enough to drive my coworkers and me up a mountain to a particularly scenic spot that is hard to get to. I rode in the backseat, and within the quarter mile up the mountain, was overcome with my first-ever bout of (severe) motion sickness. The only relief was to close my eyes and try to think happy thoughts of kittens and Anthropologie. I never saw that scenic spot, unfortunately. But I did leave my lunch, which I had eaten 2 hours prior, on the roadside. It happens.

This experience caused me to recall an experiment where an ingenious but somewhat evil scientist discovered the mechanism by which most invertebrates sense up from down. Let me explain.

In the late 1800’s, people observed newly-molted crawfish picking up small rocks and particulate from their surroundings and placing them in little cavities in their heads (called statocysts).  In 1893, a zoologist by the last name of Kreidl decided to solve the mystery behind this strange behavior. His hypothesis was that it functioned in balance or orientation, so he came up with his malevolent plan.

Kreidl placed newly-molted crawfish in terrariums with iron filings at the bottom instead of sand. As predicted, the crawfish placed the iron filings into their statocysts. And then started the fun.

He took an electromagnet and brought it close to the crawfish. When the magnet was brought close to the animal’s right side, the crawfish tried to turn over so that it’s belly was facing the magnet. Vice versa when the magnet was exposed to the left side. When held right above the crawfish, it tried to flip over onto its back. Clearly, the crawfish associated the position of the iron filings within their statocysts with the direction of gravitational pull. Ah hah!

When at rest, the ventral setae are excited.

But there’s more to this story than simply acclimating towards gravity. The inertia of the statolith (grain of sand, rock, iron filing, whatever) can also tell the crawdaddy which way it is moving. If the posterior setae are excited, then the animal experiences the sensation of moving forward.

When scuttling forward, the posterior setae are excited.

In Kreidl’s experiment, the animals showed general disorientation when the magnet was brought to the posterior. This is likely because they weren’t locomoting forward, but still felt like they were moving forward. They were all “what the hell?!” and started flipping around, searching for the sensation of gravity and rest.

Come to find out, every time a crustacean molts, it loses the lining of the statocysts and therefore the statoliths within. This explains why the statolith-gathering behavior is observable after molt. How strange this is to me: physiology dependent upon the addition of external objects to a sensory system, i.e. having to stick rocks in your head every so often. Strange, but pretty neat.

But seriously, those poor crawfish- if only they had more sophisticated cognitive abilities and inner ear complexity, I’m sure they would have felt about like I did on that mountain. If Kreidl had a mustache, I bet he twirled it and laughed the whole time.

In reality, Kreidl was not evil but super smart. His experiment was a seamless and inspired piece of scientific work. Well done, Kreidl.

Resume petting your evil cat.           

shedding light on bioluminescense

To me, one of the most horrific environments to imagine is the bottom of the ocean. It’s completely foreign and black, it’s miles from the surface, it’s under water, it’s highly pressurized, and there are scary ass animals. Among them, the deep-sea fish: most of which have one redeeming quality: light-up body parts. When it comes to glow-in-the-dark deep-sea fish, bioluminescent body parts are generally used as lures and so are feeding purposed.

Humpback Angler Fish. Yeah, good luck ever sleeping again.

Last week, an evolutionary baggage reader (Matt Martin, holla!) asked a thoughtful question. “How did deep sea bioluminescence evolve?” How can a consumer survive in the bathypelagic zone of the ocean, where virtually no light reaches, and life is scarce? What is a vertebrate doing down there to begin with?  How was bioluminescense even given a chance to evolve in such an extreme place?

Not very well. Luckily, the road for biolumeniscent evolution had already been paved by the time these deep-sea fishes sank from the middle depths to the deep. A gradual shift towards selection for those fish that could exist a little deeper and occupy a specialized niche began to occur. And so, they descended.

Within that shift, selection for increased concentration of luciferinases occurred, gradually turning into specialized organs with high concentration of coelenterazine and the luciferinases to light them up. Whoa, s*!# just got real. Let’s back up.

Luciferins are the key chemicals in the reactions that produce bio-light. A specific luciferin called coelenterazine has strong antioxidative properties (just like the antioxidants in blueberries and prunes- they bind free radicals and keep them from wrecking your cells. They’re good for you. Eat lots.) Way back in the day, the predecessors to glow-in-the-dark deep-sea fish had coelenterazine all throughout their bodies serving as antioxidants.

In the deeper parts of the ocean, oxidative stress is way less than it is closer to the surface. This is because 1. There is less UV exposure 2. There is less oxygen. When the ancient fish began to sink into the deep-sea consumer niche, the lessening physiological demand for coelenterazine as an antioxidant gave it the chance to fulfill the new demand for having a glowy dangly thing. So it began to locally accumulate, forming light-emitting organs. Of course, this was all very gradual. The glowy dangly things probably started off as a very dim photogenic patches of skin, but evolved into a specialized structure- technically known as an “esca.” Or a glowy dangly lure thing. Whichever.

Lots of other critters can glow, too. Plants, fungi, marine invertebrates, bugs, worms, you name it. But that’s a whole ‘nother can of… well, worms.

Here's the paper if you're feeling ambitious:

The origins of marine bioluminescense: turning oxygen defence mechanisms into deep-sea communications tools. Rees, De Wergifosse, Noiset, Dubuisson, Janssens, Thompson. The Journal of Experimental Biology 201, 1211-1221 (1998).

that tooth thang

Currently, I’m interning at a raptor education center. Basically, I show people birds and explain all the cool things about them. Some people come in and ask really good questions like “can they see in color?” or “do they mate for life?” However, some people ask not-so-intelligent questions. The other day, a young presenter was holding an Eastern Screech Owl and was asked by a guest “what is that tooth thang in the middle of its face?”

The guest was referring to the bird’s beak.

Of course, I mentally shook my head and entertained thoughts about how ignorant one must be to not know a bird’s beak when one sees it. But later on, I began to think that maybe I was being narrow-minded. Is it so dumb so register a tooth and a beak in the same category? Could the beak be the evolutionary cousin of teeth? Perhaps.

I started looking into the matter, this time with my mind set to evolution mode. When you think about it, beaks are pretty unique and useful structures. Birds have them, and even turtles kind of have them. Some are curved into a sharp points and tear flesh. Some are flattened into a bill and sift solids from water. Some are heavy-set and can crack macadamia nuts with no problem. Others are long and tubular, perfect for sticking down into a flower and licking out nectar. Though avian beaks are diverse now, it does not change the fact that modern birds came from a single common ancestor from Dinosaura. So the beak came from a single evolutionary point. That begs the questions- why, when, and how?

Lindsay Zanno and Peter Makovicky published a study in Proceedings of the National Academy of Science where they used a wide variety of evidence to figure out what therapods ate (theropods are the two-legged dino forebearers to birds). Evidence included fossilized dung and tooth marks on fossils (remember what fossilized poo is called?! Brownie points!). They found that early therapods were largely herbivorous, but some later evolved to be omnivorous and eventually carnivorous.

Come to find out, beaks emerged FIVE separate times within Therapoda. The diverging phyla of little herbivorous dinos experienced the drift towards and pressure for omnivory, which favored selection for having a beak. One lucky lineage went on to spawn our friend Archaeopteryx, and consequently, all of the birds both past and present.

The real kicker here is that these early beaked creatures still had teeth. I entertained this lady’s question thinking that perhaps the beak arose from the same germ cells as the teeth. But no siree, teeth were still present within the beaks. Therefore, teeth are not the structural forbearers to the beak. Not even on a germ line level.

If the lady who asked about the owl’s beak was asking because she thought maybe the beak was the product of increased selective pressure for a ripping mechanism over grinding teeth, like herbivorous therapod forebearers had, then that question was pretty good. Bravo.

But judging by her description of the beak as that “tooth thang,” my first instinct was right. That lady asked a really, really, dumb question.

polo blue and sloth poo

Instead of writing the usual first paragraph of lazy bloggers that apologizes for “not writing for so long” because of “how busy” I’ve been, I’m going to spare you the crap and go ahead and jump right in to a related (yet actually interesting) topic: sloths.

Sloths are the poster animals for laziness. They move really slowly and spend their entire lives in the trees. They exhibit few behaviors aside from eating, pooping, and mating (doesn’t sound so bad, I know). While they themselves are exceptionally interesting, they really do not possess any exceptional senses. Their eyesight is so-so. Their hearing is “good-enough.” Their sense of smell is existent but not super sensitive. You could say their most extreme qualities are their cuteness and their ability to hang on to stuff.

These solitary animals move so slowly that they rarely encounter each other. After leaving their mothers as babies, they begin to disperse and live by themselves. Adult sloths are spread throughout the jungle, slowly lumbering around in the trees unable to hear, see, or smell other sloths. Which is fine (and even nice, if you are one who prefers sloth bachelor-hood) until it comes time to fulfill that little ole’ purpose for existing. How do sloths find each other when it comes time to procreate?

They have really, really, smelly poo. So smelly that all the animals within a few square miles can smell it. A frisky sloth will slowly make its way towards the smelly, pheromone-laden poo until it encounters the poo or the maker of the poo. And chances are the maker of the poo isn’t that far away from the poo, seeing as they move at the speed of, well, sloths.

Can you imagine having to smell your way to a potential mate by… their poo? Thank goodness humans don’t function like sloths in this regard. I definitely prefer sniffing out Ralph Lauren Polo Blue or Very Sexy For Him 2. Just sayin’.

P.S. I am sorry for being such a sloth of a blogger. From here on out, I promise to write with the determination and motivation of a sloth trying to find another sloth’s poo. Sloth’s honor.

i don't know nothin' bout birthin' no porcupine babies

Let’s just dive right in. How much must it suck to birth a porcupine?! Yeah, bet you never thought of that before.

Luckily, nature has addressed this issue. But for suspense, I’ll save the solution to this prickly problem for the end. First, let’s cover a little background knowledge about our splintery mammalian cousins.

Porcupines are big rodents, kind of like beavers. In fact, a porcupine’s front teeth are just like that of the beaver. They are found in North America, concentrated in Canada and Alaska. Their rumps are covered in quills that lay down towards the rear. When the porcupine becomes agitated and feels the need to defend itself, it bows its back up like a cat. Its quills raise up in a primed a ready position. 

Quills are modified hairs that are reinforced with lots of stiff keratin. They can grow in clusters or can be evenly spaced out, depending on the species. Quills are embedded in the muscles directly beneath the skin. Since the quills are akin to hair, they can fall out as part of a natural replacement cycle, or they can be pulled out by force. These lethal weapons conjure images of blood and strike fear in the hearts of people, making the porcupine one of the most misunderstood animals around.

Being attacked by a porcupine and ending up with painful quills sticking out of your flesh is a highly improbable event. Porcupines are slow and lumbering creatures. Moreover, they cannot shoot out their quills. If an animal sees a porcupine as prey and throws its own body upon it in an attack, quills will become lodged in it. But a porcupine has no ability to shoot out its quills like Spiderman does spider webs. When you combine this revelation with the fact that porcupines cannot chase you down, the only thing you have to worry about is accidently stumbling upon a porcupine. And if that happens, well, it’s just in the cards.

Now let’s reveal the secret behind birthin’ porcupine babies. First of all, a porcupine baby is called a porcupette. And thankfully for porcupine mamas, porcupettes are furry little fluff balls. Their quills are present but not yet hardened. The keratin hardens within the first few weeks of life, making the birthing process not too horrible. Evolution gave mama porcupines a break on this one, thank goodness.

And now, let me leave you with some pictures of porcupettes. 

You're

welcome.

slutamanders

I know, I know. I’m worthless. I apologize for the lack of consistent posts. Or really, the lack of recent posts, period.

These past two weeks have been very busy. I wrapped up my illustration gig in Auburn, moved back to Louisiana, and repacked everything to move to Alaska. (I’m on the flight between Dallas and Seattle as I write this.) Once I get settled into my new surroundings, I promise more consistent (and likely raptor and Alaska-themed) blog entries. Excuses, excuses, I know. You don’t want to hear it. You want to hear some science, don’t you?

Salamanders are a curious bunch. I bet there is a population within a mile of where you live, and you don’t even know it. They’re small and hang out under logs and damp earth. Not the flashiest or most gregarious amphibians, but common and pretty darn cute.

A particular family of terrestrial salamanders- the Plethodontids- are particularly interesting. Their small size allows them to breathe entirely via diffusion through their skin (therefore, they don’t have lungs). Their small size also means their brains are about the size of a very small piece of orzo. All of their life functions and behaviors are products of a relatively basic operating system.

That makes their complex mating behaviors even more astounding. The males will do little dances around females. The males also have a gland on the underside of their chins (this is actually how you sex them in the field) which they “snap” on the female to make them… frisky. When she is ready, she’ll nudge him with her face and he releases little sperm packets in a little line. She walks over them and picks them up with her cloaca (use context clues if you don’t know what a cloaca is). No hanky panky- as we know it. But this system has worked well enough for millions of years for these little guys.

Mate fidelity during single breeding seasons has been known to occur in Plethodontids. However, one species has taken it to the next level. There’s this one study in which mate punishment was observed in Plethodon cinerus. By mate punishment, I mean females will beat up their mate if she detects another female’s scent on him. Sometime’s he’ll sneak off and “slip up” with the female from the rock down the stream. When he comes back, his main lady will bite, bump him, smack him, and generally abuse him. Mind you, they’re no more than 2 inches long. So this is especially funny. Scientists observed that the male does not fight back, but instead just takes it. He knows what he did. Reminds you of a bipedal primate, huh?

We humans display mate punishment too. Be it yelling, hitting, revenge, or the silent treatment, we participate in just the behavior. Luckily, we are civilized and (some of us) know to beat down feelings of petulance and handle such issues with grace and maturity. However, could it be that our jealous romantic retribution is an evolutionary seed planted long ago in our history, as in the case of these slutamanders? Or is it the result of Jersey Shore showing us how Sammy Sweetheart makes Ronnie regret his infidelities?

As usual…. probably both. Isn't it something how this behavior is characteristic of a brain the size of orzo AND a brain the size of a football? We have more in common with our terrestrial tetrapod friends than just morphology. It's important to remember that behaviors evolve too.

in honor of the gill

Since it’s my best friend’s birthday this week, we’re going to talk about how fish gills work. (Her name is Ashley Gill. So it’s only fitting.)

The need to breathe is common to almost all organisms on earth. Breathing, in the broadest sense, is taking in an environmental element, extracting part of it for metabolic use (i.e. oxygen), and expelling the leftovers.

Critters live in all sorts of environments, so naturally there are varying methods of breathing. Air breathing animals, as a rule of thumb, use lungs. Animals that must take in water usually use gills. Sometimes animals do not have breathing structures at all and simply absorb what they need through their skin, via water or air. Well that sounds easier, doesn’t it? Why can’t we all just do that? Surface area, baby. That’s why.

Generally speaking, when an animal becomes big enough to exceed a specific volume: surface area ratio, they are no longer capable of meeting metabolic needs by absorbing oxygen through their skin alone. They simply need more tissue devoted to extracting oxygen from their environment to supply their bodies. Enter respiratory structures like gills and lungs.

Fish gills looking nice and feathery

When you think of gills, the first thing that should come to mind is surface area. Gills are made up of projections, with tiny projections on those projections, with tinier projections on those tiny projections (these tiny projections are called lamellae). As such, the result is the feathery looking thing we call a gill. These tissues are laden with blood vessels, which allow for oxygen exchange between the water and bloodstream.

A fish breathes by drawing in water into its oral cavity, then into the gill chamber, and out of the gills. This means there is a constant one-way flow of water over the tissues of the gills. A one way flow of water, huh? We have a two-way flow through our respiratory system (we breathe in, then out). Fish must know something we don’t. Let’s talk counter current exchange.

Now for some real-deal biology. In the lamellae, the part of the blood vessel coming in with deoxygenated blood is afferent, then it makes a U-turn and becomes efferent, carrying away oxygenated blood to the body. Somewhere between being afferent and efferent, the blood vessel follows alongside the current of water… in the opposite direction. This is the magic of countercurrent exchange. Blood flows in the opposite direction of water.

This way, the blood always has a lower concentration of oxygen than the water it encounters. Water will always give its oxygen to blood via passive diffusion when the oxygen is distributed this way. In a concurrent system, where water and blood flow in the same direction, the oxygen will balance out equally between blood and water, making maximum oxygen saturation of the blood 50%. Countercurrent exchange beats this by a lot, having 85% oxygen saturation the maximum. I could try to further explain this in words, but a visual is what’s really needed.

                            

                          

Neat, huh?! Simple and efficient. This is just another example of how newly evolved things are not necessarily better than more primitive things, like gills.

This week, we have two bonus questions. If you’re the first get one right, I will do one of two things. 1.) Write a blog on the subject of your choice 2.) Include you in an amusing way in an upcoming post. I can’t promise I won’t photoshop your head on a monkey or something if you select this option.

So c’mon! Play along. Please. I’ll pay you. No, I can’t afford to pay you. I’ll love you instead.

1.What do you think is the foremost reason fish are unable to extract oxygen when out of the water?

2. Are lungs the evolutionary descendents of gills? Explain your thoughts.

I would say there are no right or wrong answers here, but that’s not true. But not to worry, it’s the process of thinking about it that makes winners on this blog!