Biochemical Soul Musings on Nature, Science, Evolution, Biology, and Education

12Feb/09Off

Darwin and the Heart of Evolution

Happy 200th birthday, Charles Darwin!
Happy 200th birthday, Abraham Lincoln!
Happy 150th anniversary, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life!
And here's to a happy Darwin Day and upcoming Valentine's Day to everyone else.

As a part of my own contribution to the Blog for Darwin campaign, I present to you "Darwin and the Heart of Evolution."

What do all four of the above events have in common, other than being events of celebration? The answer will become obvious, but as a clue, I will begin with an appropriate Valentine's question:

A Frog's Heart

A Frog's Heart

Why do humans have hearts?

I can see it already – you’re rolling your eyes thinking, “Well duh…because we need a way to circulate oxygen, hormones, immune cells and other signals, and transport waste compounds and gases.”

Ahh, but you would be wrong. For the above describes only what a heart does – not why we have one. As I wrote a few days ago, evolution pays no attention to "needs." Species don't evolve because they "need" to adapt or change some trait. Natural selection is blind to all intention and desire.

Before Charles Darwin (and his buddy Alfred Russell Wallace) gave us the theory of natural selection, the above "necessity" explanation would have sufficed – with an added “because God designed it that way” just for good measure.

The genius, beauty, and simplicity of Darwin’s big idea was in how it utterly reshaped the manner in which all “why” questions about reality are posed and how their answers are understood. The Origin of Species laid the foundation for the complete upheaval of the very word “why.” In fact, when it comes to describing biology, astronomy, physics, geology, and every other empirical look into reality, the word “why” now means nothing more than the word “how.” The how is the why.

So again, I ask - why (how) do humans have hearts?

To answer this question we need to jump back about 500 million years ago into the ancient ocean. Based on the fossil record, this is a good date to pick, considering that worms don’t make great fossils; however, the exact date is not at all important for this discussion. Nor does it matter the exact species of worm-like creature we consider, or the exact details of the hypothetical time-traveling adventure upon which we will now embark.

Imagine it - we’re swimming now in the ancient ocean sometime after the massive explosion in the evolution of all sorts of strange ocean-dwelling invertebrate body forms (the Cambrian explosion). One of the many advantages that certain individuals of various species find is that their larger body sizes makes them better able to compete – up to a point. Once a small early worm-like species reaches a certain size, it finds that it cannot grow any bigger with its current body plan. This is because at this point, our hypothetical creatures do not have circulatory systems. They must absorb all their oxygen from the surrounding water. Any individuals born larger than a certain size can no longer get enough oxygen due to the oxygen not reaching deep enough into their tissues, and so they die (or are our-competed).

The Vertebrate Family (image credit)

The Vertebrate Family

Now imagine an individual of this species is born with what others of its species would consider a defect (if they had brains with which to consider such a concept). This individual has certain cells that have formed a small simple tube-like structure. Perhaps it is only a vague cavity – or some extra space between its cells. Now when this individual swims around, contracting its primitive muscles, the fluid within its body spreads a little bit more and a little bit faster through this cavity or space.

Our little worm leads a happy life, finding mates (or perhaps reproducing asexually) and leaving an ocean full of cavity-containing offspring. It seems self-evident to us now, but Darwin found himself surprised at the amount of variability in traits throughout the animal kingdom. All populations vary; thus, some of our worm’s children are a little bit bigger than their siblings. And some of these worm children will have inherited papa worm’s fluid cavity, which meant that they could survive with a slightly larger body than those without the primitive vessel, due to the oxygen distributing power of the fluid filled vessel.

Thus began the evolution of the heart. By a series of easy to imagine steps through thousands or millions of generations, the cavity became slightly more developed, eventually forming an actual tube. I would like to note here that the above scenario is strongly supported by much embryological, anatomical, and genetic data. However, I would like keep this simple and vague for the layperson.

Now, we move forward in time, though how far is unclear. Our little worms are now bigger worms, insect ancestors, and a myriad other small invertebrate species. Some of these species have evolved their tubes to have contractile regions - that is, a region of the tube than can actually squeeze and pump. Some, like our modern earthworm, have seven of these pumping “hearts”. Others, like the Drosophila fly, have only one heart - called a "dorsal vessel" (see the Drosophila larvae movie below).

Fish Heart

The Fish Heart

We swim forward to 525 million years ago, just as the first fish appear in the fossil record. A lineage of the invertebrates has slowly morphed through primitive chordates (organisms with a nerve cord) to become the most primitive fishes. Along with the changes in many other body structures, the basic contractile heart and vessel system has itself become more complex. Instead of one contractile chamber, the fish heart has divided into two chambers: an atrium and a ventricle (and a stretchy region called the conus that isn’t contractile). The fish themselves then radiate over time, each lineage slowly accumulating many small changes, resulting in the gradual evolution of an ocean teeming with fish species – all with two-chambered hearts (see image at right).

Eventually, some fish species start shacking up near shorelines or in shallow ponds and lagoons. Some are born with thicker fins, which allow them to push along the bottom of the pools a little more quickly or lithely than others. They mate, and the process continues. Finally, one of them decides to just get it over with and leaps out of the water to land as a frog on four fully-formed legs.

The Amphibian Heart

The Amphibian Heart

Not really, but you get the picture.

We now see amphibious creatures roaming the shorelines like beastly salamanders. Their hearts have changed even further as other aspects of their bodies evolved to take in oxygen through lungs. Why did this happen? Because the changes that make it possible did happen. These shallow water-dwelling creatures began to develop vessel-filled outpockets on their esophagus, giving them the advantage of pulling oxygen from the air. In addition, the individuals with slightly better circulatory systems found their bodies better at all sorts of other things, such as regulating their bodies with hormones and getting rid of cellular wastes.

At this point, a series of further changes occurred in the amphibian heart. The atrium became two separate atria, either through a physical division of the one atrium, or through a duplication of the vessels coming into the heart. Thus, the frog ancestors developed three-chambered hearts, which were subsequently passed down to every frog currently inhabiting the earth (see image).

The Reptile heart

The Reptile heart

As time passed, the frogs began drying off their slime, sprouting scales and forked tongues, and inspiring instinctive reptilian nightmares in their prey. They became lizards. As the lizards moved fully to land and grew even larger, certain inherited variations in their hearts naturally worked a little better – thus natural selection continued the continuous sculpture of life. The ventricle began to separate into two chambers, much like the atrium had done in the amphibians. However, the ventricles didn’t fully divide. As one can see in almost every reptile on earth today, the ventricular division is incomplete – almost like a four-chambered heart, but with a hole between the ventricles (see image). However, I said that almost all reptiles have the pseudo four-chambered cardiac morphology; in fact, one branch of the reptiles went on to develop a fully-featured, true four-chambered heart: the crocodile - but that's a side story.

From some of the lizards the dinosaurs then sprung forth, populating the land from the small dark corners to the open plains. A short while later (a paltry 170 million years) most of the dinosaurs died off. Along with their distant crocodilian, lizard, and snake cousins, at least one dinosaur lineage and one reptilian lineage survived. We now call them birds and mammals, respectively.

Both the bird and mammalian lineages mirrored the path of the crocodile, completing the division between the ventricles (probably prior to their divergence). Natural selection has continued to sculpt our own mammalian hearts, resulting in marvelous structures such as the multiple different valve types, chordae tendenae ("heart strings"), and trabeculae (fibrous strings in the ventricle's interior).

The Bird and Mammal Heart

The Bird and Mammal Heart

And with that, we have answered our initial question, in a massively oversimplified fashion. We have hearts because each change leading to our hearts conferred some small advantage to the individuals that inherited them (or at the very least, were not disadvantageous).

Of course, all of these cumulative small changes in the shape of the vessels and hearts, ultimately involved millions of small changes in the genes that controlled the behavior, shape, and functions of the circulatory cells. Scientists have now discovered an incredibly large and complex network of such genes controlling development of the heart.

One of the most astonishing yet completely expected facts we have garnered through studying organisms from Drosophila to the African clawed frog (Xenopus) to humans is the discovery that every organism on this planet with some version of a heart contains the same or a similar set of genes to control heart development.

That’s right. Read it again.

Many of the genes involved in the formation of the relatively primitive “dorsal vessel” in a fly are versions of the same genes that initially form our own hearts. Think about that! Think about how massively more complex we are compared to flies (which are themselves insanely complex in their own rights). Think about the hundreds of millions of years that separate us from our most recent common ancestor with a fly. Yet your heart still uses many of the same genes and in the same ways during early heart development. Of course flies and humans have continued to evolve in parallel ever since our lineages split those hundreds of millions of year ago – we have both made countless changes and tweaks to our own cardiac programs and networks. Nonetheless, our hearts remain related.

In fact, if you watch heart development in an embryo, such as in the Xenopus movie below, you can almost see the course of heart evolution itself. Of course this isn't really ontogeny recapitulating phylogeny - but some of the evolutionary history behind cardiac development is at least evident.

Tbx20 expression in a frog larva heart

Tbx20 expression in a frog larva heart

One example of a cardiac gene that I’m particularly familiar with, having received my doctorate studying it, is a gene called “Tbx20”. For this discussion, its exact function does not matter. Suffice it to say that when I began my studies, we had a clue that this gene was important in heart development. Why? Because flies have a copy of this gene, as do humans, mice, and every other heart-bearing organism we’ve looked at; furthermore, in each of these organisms this gene is “turned on” in the developing heart tissue.

I went on to show that when you prevent frog larvae from making the Tbx20 protein, they develop incredibly malformed hearts (see the videos below). This means that the Tbx20 gene is indeed important in making a heart. Other researchers later went on to show similar results in mice and flies. Finally, about two months before I finished graduate school, another group of researchers found that some humans born with congenital heart defects have mutations in the Tbx20 gene.


Normal African Clawed Frog (Xenopus) heart


African Clawed Frog (Xenopus) heart lacking Tbx20 protein

So here we have found in only a few years of research a single gene that supports the entire model of evolutionary theory. To rephrase the famous quote from Theodosius Dobzhansky, the existence of Tbx20 in controlling the development of the heart in organisms from flies to humans does not make any sense – except in the light of evolution.

Due to the rich evolutionary history behind the development of this complex organ, the genetic network has become incredibly complex, involving hundreds of genes in thousands of cells all working, moving, and functioning in precise coordination. The higher the complexity, the more things that can possibly go wrong. Unsurprisingly, congenital heart defects are among the most prevalent of all inherited diseases, resulting in about 9 babies out of every one thousand being born with some sort of cardiac abnormality.

I’m sure many of you were wondering how I would manage to tie Abraham Lincoln tie into all this. Although still hotly debated and unproven, at least some researchers believe that Abraham Lincoln may have been afflicted with a disease called Marfan Syndrome, a connective tissue disorder affecting the heart and many other organs. Other researchers believe that he had an unrelated disease. Regardless, it remains at least possible that President Abraham Lincoln was the inheritor of one of the billions of less advantageous variances in heart development that have presented themselves throughout the heart’s evolutionary history.

In summary, the heart of Darwin's theory of natural selection is the idea that evolution comes not through the "why." It comes through the how - through the accumulation of minute individual variations that spread like wildfire when they contribute an advantage.  There remains no better demonstration of this principle than the myriad heart morphologies and functions we can trace today.

Each of you has most certainly inherited a cardiac variation, whether it be a major mutation in a gene, or a tiny change in one letter of your genetic code (a "single nucleotide polymorphism").

Who knows...perhaps yours is the one upon which an entirely new evolutionary history will be built.

So here’s to your own personal variation, and to the man who made our understanding of it all possible. We would have gotten there without him – but I doubt anyone could have rivaled the combination of his incredible intellect and beautiful prose.
Happy birthday Darwin!

_____________
Image credits

Frog heart photograph: Me
Phylogenetic tree: McGraw-Hill and Biology Corner
Drosophila heart tube movie: unknown
Heart diagrams: Oracle ThinkQuest Education Foundation
Cardiogenesis animation: Me
Frog heart movies: Me
Lincoln photograph: Visiting DC

Lincoln photo:

5Jul/09Off

A Tale of the Hunt for Fossil Shark Teeth

As someone who has been a lifelong fossil collector, I have a terrible, unforgivable sin to admit: I lived for eight years in North Carolina and never knew of the existence of Aurora, NC.

Mind you, since moving here for graduate school, fossil hunting had fallen off of my priority list, largely owing to the fact that central Carolina rocks are basically all metamorphic (melted and recrystallized by heat and pressure). And I've never been the gung-ho research-fossil-sites-and-go-hunting type. Since I began collecting while living in the Ozark mountains, it was more of a walk-through-my-parents-woods-and-see-what-fossils-I-find-today sort of hobby, with a few far-flung excursions in the mix.

Well that all changed a few weeks ago. My wife, some friends, and I spent a couple of days at Topsail Beach, NC.

Actually - scratch that - it began a few month's ago, when Christie at Observations of a Nerd reported an awesome find of fossil shark teeth in Florida, and then - like the wonderful person she is - sent me a handful of them.

Shark Teeth from the wonderful Christie

Shark Teeth from the wonderful Christie (Note to Christie - they are ray dental plates - not stingray barbs - just learned that - see below)

Back to Topsail Beach, circa a few weeks ago.

I said to myself, "Self - it's the ocean - there are bound to be fossil shark teeth. You (I) will not allow me (myself) to leave this beach without finding at least one shark tooth."

So I spent all my beach time on Saturday perusing the sands for teeth.

To no avail whatsoever. I never saw one.

The next day, I began again, searching much more intently. While combing the fresh tide-swept beach, I saw a tiny black triangle amidst the shells. It was a shark's tooth!!

The filters through which my perception is sifted were now calibrated. Within the next few hours I had a nice handful of tiny teeth. I was ecstatic.

(Note for the fossil pros and beach inhabitants out there: feel free to laugh at my ignorance of what constitutes awesome shark teeth. But these were just about the coolest things I had ever found - at the time.)

Hold your applause - you aint seen nothing yet

Hold your applause - you ain't seen nothing yet

Tiger Sharks - grrrr...er...meow

Tiger Sharks - grrrr...er...meow

Thus was I hooked on shark teeth.

The next necessary stops in my tale are the mountains of West Virginia and hills of Pennsylvania.

Some of you know that I will recently begin a new job at Carnegie Mellon University. As such, we have driven there twice recently. I am utterly awed by the massive amount of roadcuts through the mountains of the two states, all of which reveal millions upon millions of years of Earth's natural history in it's geological strata. I felt the fossil-hunting bug really kick up several notches while driving through those strata.

Thus, in anticipation of my move, I began hunting online for potential fossil sites in Pennsylvania. In this endeavor I discovered The Fossil Forum. Through this forum, I discovered not only a huge community of avid fossil hunters, experts, and enthusiasts, but also that North Carolina has some of the most amazing shark tooth sites in the country.

"Self," says I, "it's bad enough that you've been here so long without discovering North Carolina's fossil sites - but now you are leaving? I forbid you (myself) from leaving until you have visited these sites. Got it?"

It was decided - the July fourth weekend was my only free one from now until the move, thus I would make it a fossil-hunting weekend. I would spend Friday in Aurora, NC and Saturday at Green's Mill Run, a creek in Greenville, NC.

As fate would have it (though we will soon see that the result would have been the same with any weekend, fate or no) a dude by the name of MikeDOTB (Michael Taggert) on the Fossil Forum, was also making the exact same trip this weekend. We decided to meet at the shark-digging piles at the Aurora Fossil Museum on Friday (Note to parents in NC - TAKE YOUR KIDS HERE! Free digging teeth by the thousands to their little hearts' content). Mike said he would be there by 7AM and I would try to get there by 9AM (it's a 3.5 hour drive for me).

NOTE: See Mike's Trip Report here - he has some amazing shark teeth!

I was too excited. I couldn't sleep at all the night before. So I slid out of bed and out the door at 3AM arriving at the piles in Aurora by 6:30AM. (The piles are Pungo River Formation sediment - age ~18-22 million years -  donated by the nearby PCS phosphate mine).

It was just me. Not a soul in sight anywhere. Alone - in a beautiful dawn with giant piles of Miocene sediment to sift through at my leisure.

I saw my first tooth within about ten seconds of glancing at the piles. My collection grew fast and linearly from that point onward. Before too very long, a nice man showed up to sift as well. It turned out that he was a Fossil Forum member too (runner50) - a Kansas Science teacher on a trip around the country to spread his recently deceased wife's ashes at their favorite locations (including St. Claire, Pennsylvania which has some amazing fern fossils, which he showed me). Many of the ancient teeth he was collecting were for his students/class. Despite the sadness of his tale, it was incredibly heartening to meet such a man teaching in Kansas, a place we all probably know needs good science teachers!

In the wild

In "the wild"

Mike showed up later than he had planned, but as soon as he got there we hit another nearby pile, meeting a guy named Brian in the process. We chatted for quite a few hours as the three of us sifted for teeth in a couple different locations. Brian, another Fossil Forum member, gave me a dolphin vertebra among other things.

Dolphin Vertebra - Thanks Brian!!

Dolphin Vertebra - Thanks Brian!!

Fossil enthusiasts are awesome people, based on the few I've met!

Mike, Brian, and Me - sifting the piles in Aurora, NC

Mike, Brian, and Me - sifting the piles in Aurora, NC

Mike, showing how its done with his giant 1/2 mesh screen

Mike, showing how it's done with his giant 1/2'' mesh screen

The piles

The piles

I almost look like a real paleontologist. Or not...

I almost look like a real paleontologist. Or not...

Before the day was up I had amassed a huge pile of little shark teeth, though no lunkers had given themselves up. I had already watched in envy as Mike pulled several beautiful teeth from the piles. However, I wasn't really jealous, as I was too excited from the insane numbers of teeth I  was finding with my smaller 1/4" mesh screen. After about 13 hours straight (no lunch break or anything), darkness began to loom. So Mike decided to collapse the pile we had been digging into. Wet internal sediment began falling and we both began picking through it as more fell. In about a third of a second a shiny glint caught my eye in the muddy dirt. I snapped at it like a greedy hungry chicken.

It was a big Extinct Giant Mako (Isurus hastalis)!

Extinct Giant Mako make-o me happy

Extinct Giant Mako make-o me happy

Also, it had a small bit of feeding damage at the very tip (which makes it only cooler to me). Now go back and compare that to my first teeth from Topsail...

Without further ado, I give you the rest of my collection from Friday, filled with makos, tigers, sand tigers, snaggletooths, cow sharks, and even one small  nearly complete tooth and some pieces of megatoothed sharks (C. megalodon and/or chubitensis).

Note: I have zero tooth ID skills, so forgive any errors. There are almost certainly teeth "out of place"! I arranged these pretty quickly.

(Click for larger)

The Catch

The Multi-Million Year Old Catch

Arent they pretty?

Aren't they pretty?

A few of these were given to me by Mike - I don't remember which ones. Thanks Mike! He also gave me the coolest thing I now own...keep reading.

Tigers and Snaggletooths

Snaggletooths and Tigers

Sand Tigers et al

Sand Tigers et al

Megalodon/Chubiitensis?

Megalodon/Chubitensis?

Makos, Giant megalodon chunck, and others...

Makos, giant megalodon chunk, and others...

Lemon sharks and others?

Requiems, Coppers, Hammerheads? No idea...

Broken cow sharks

Broken cow sharks

Ray dental plates (for grinding munchies)

Ray dental plates (for grinding munchies)

The little guys (Mike estimated ~1200 total teeth)

The little guys (Mike estimated ~1200 total teeth)

Did you know a single shark can go through 30,000 teeth in a lifetime?

Did you know a single shark can go through 30,000 teeth in a lifetime?

And of course, I found some other cool stuff as well...

Shark Vertebrae

Shark Vertebrae

How cool is that?

How cool is that?

Coral

Coral

Love the detail in these things!

Love the detail in these things!

So I had a great haul - and searing back and arms as payment to Mother Nature for her bounty. But back pain or no, we had another whole day to go.

Mike and I high-tailed it to Greenville and crashed at the Motel 6, after spending at least an hour rinsing and gawking at our fossils. Mike gave me most of his teeth, except for the near perfect ones he deemed fitting for his collection. What an awesome dude!

Then again, this is a guy who has 30,000 teeth! Also, he seemed to know every single shark species, their scientific names, whom is thought to have begat whom evolutionarily, and he could instantly tell the ID of each tooth. Oh yeah, and remember how I said "Fate" had led me to want this trip at the exact same time that Mike announced that he was planning a trip? Yeah, well, he has gone on this trip almost every weekend since January.

Yeah - he's an enthusiast alright... Thanks Mike - you rock!

We awoke the next morning and headed for the dirty, trash-filled, broken glass-laden creek running near East Carolina University campus known as "Green's Mill Run." This place is famous for yielding big megalodons and great whites (and ancient soft drink bottles and bongs). The creek cuts through layers from the cretaceous to the pliocene, so things found in it can range from about 2.5 to 145 million years old!

The story was much the same at "GMR". I found quite a few great teeth (though I didn't feel as inclined to pick up every tiny tooth after the previous day), including another awesome Mako.

This was while I was still clean...

This was while I was still clean...

Mike found an AMAZING great white, and lot's of other great teeth - many of which he gave to me.

Mikes Great Whites - beautiful

Mike's Great Whites

I sat and watched an awesome freshwater eel hunting minnows in one beautifully sunny pool - a first for me. We didn't have freshwater eels in NW Arkansas (that I'm aware of).

Mike found and gave me what I easily consider the coolest fossil I now own (he already has several): the fossilized inner ear bone of a whale. What kind? not a clue.

Whales inner earbone

Whale's inner earbone

We visited one particular spot in the creek that cuts through this crazy shell layer filled with huge scallops and various mollusks.

Sea Scallop (as opposed to land scallop)

Fossil Sea Scallop (as opposed to land scallop)

Some sort of big bivalve - and WHOLE!

Some sort of big bivalve - whole and heavy!

By 6PM my back and arms would not let me sift a single more shovel load. Thus we called it a day.

Here's the total haul from Saturday:

The GMR Catch

The GMR Catch

What would have been HUGE megalodons, a very nice Mako, and a root-less great white

What would have been HUGE megalodons, a very nice Mako, and a rootless great white

The Makos and the White

The Makos and the White

The other shark teeth

The other shark teeth

Another cool fossil that exists by the millions in GMR is the belemnite. Belemnites were cephalopods related to modern cuttlefish. Only one part of it's body is normally fossilized: a calcite rod in it's body that assists in maintaining proper buoyancy. These things are just cool looking - orange and long and pointy, with a translucent character in the water.

Fossilized Belemnite guards (or rostrum)

Fossilized Belemnite guards (or rostrum)

And finally, the creek has quite a lot of pieces of whalebone:

Fossilized whale bone

Fossilized whale bone (and a cretaceous oyster - according to Mike)

All in all, this was by far the coolest natural history excursion I've been on (or perhaps second best behind a trip to Big Bend where I found an ammonite 4 feet in diameter - I left it there).  If you read this far - I hope you enjoyed my tale. If you didn't...well... you can't see this anyway.

The total weekend haul!

The total weekend haul!

Cat included for scale :)

Cat included for scale :)

Next up: fossil hunting in Pennsylvania in the next month or two! When exactly or where I don't know. But it will be fun!

18Apr/09Off

Nature Walk #4.1 – Arthropods

Spring is Here!

Days like these remind me what I love so much about the South...warm Springs exploding with life.

This edition of my series of Nature Walks is a big one. I took all of the following images over the past few days - some on my lunch break, some at the NIEHS campus, some at home, and some simply next to the road on my daily commute. So perhaps "Nature Walk" is a misnomer for this edition, but it suffices. Even while staring at the lake through my windows at work I am walking nature in my mind (unless I'm sectioning brains).

I've broken this post up into four parts due to the large number of images:

The images are highly compressed for bandwidth's sake, but you can click on the images for larger versions (and a few are much deserving of an extra click).

As always feel free to give me any species identifications where I have failed to do so or done so incorrectly.

Arthropods

The first thing I'd like to note is that if you haven't visited Bugguide.net before, you should check it out.  It is an utterly indispensable online reference for everything arthropod. I almost never fail to identify insects using it (and it has quite a few experts and educated amateur entomologists always willing to help in identification).

My wife walked into the house white-faced a couple of days ago. She had gone into my shed for a tool.  This is what she saw:

Dolomedes tenebrosus spider

Dolomedes tenebrosus spider

Dolomedes tenebrosus spider

"Go ahead - touch me - I dare you"

Dolomedes tenebrosus spider

Dolomedes tenebrosus spider

It's a Dolomedes tenebrosus spider. She's a lovely beast. She keeps my shed relatively bug-free.

I saw this next spider at the pond back behind my property today. It's a Six-Spotted Fishing Spider (Dolomedes triton). Interestingly, I learned that it is of the same genus as the monster above, though they are massively different in size, color, habit, and habitat. They both belong to the family of Fishing Spiders (though the first one does not live on water).

Dolomedes triton spider

Dolomedes triton spider

Dolomedes triton spider

Dolomedes triton spider

While turning over some leaves, I found this brilliantly colored orb-weaver, (I believe it's a Marbled Orbweaver (Araneus marmoreus)).

Marbled Orbweaver (Araneus marmoreus)

Marbled Orbweaver (Araneus marmoreus)

At lunch I struggled to capture an image of this stunning beauty of a Coleopteran. It would sit still as I focused, then dart about a foot forward in a blink - I would move, refocus - rinse and repeat... It's a Six-Spotted Tiger Beetle (Cicindela sexguttata). What luck! Two different species with "Six-spotted" in the common name (the beetle and the spider above).

Spotted Tiger Beetle (Cicindela sexguttata)

Spotted Tiger Beetle (Cicindela sexguttata)

Spotted Tiger Beetle (Cicindela sexguttata)

Spotted Tiger Beetle (Cicindela sexguttata)

Of course, the Azaleas are in full bloom at the homestead, and are of course covered in bees, flies, and butterflies.

Here's a Eastern Tiger Swallowtail (Papilio glaucus).

Eastern Tiger Swallowtail (Papilio glaucus)

Eastern Tiger Swallowtail (Papilio glaucus)

Next is the Eastern Carpenter Bee (Xylocopa virginica). I know they are carpenter bees because they drill into my wood-paneled house. This is followed by hungry red-bellied woodpeckers drilling into said wood to retrieve the hymenopteran snacks.  This is followed by me patching and repainting the woodpeckers' hack job. It's a semi-circle of life.

(Note: If you haven't seen it, you must check out my story from earlier today: The Carpenter Bee and Her Mate: A Heartwarming (and Dissapointing) Tale of Rescue.

Eastern Carpenter Bee (Xylocopa virginica)

Eastern Carpenter Bee (Xylocopa virginica)

A bee (Anthophila (Apoidea) - Bees) of unknown identity (I couldn't even peg it to a family - help please? It was about half the size of the carpenter bees.

Unknown Bee

Unknown Bee

And some Ants (Formicidae) on a flower. I didn't even realize they were there until I checked out the image on my computer.  It was a tiny flower.

Unknown Ants

Unknown Ants

Finally, I found a nice specimen of what I believe is a Carolina Mantis (Stagmomantis carolina) ootheca (egg case).

Carolina Mantis (Stagmomantis carolina)

Carolina Mantis (Stagmomantis carolina)

Carolina Mantis (Stagmomantis carolina)

Carolina Mantis (Stagmomantis carolina)

See the rest of this Nature Walk:


12Apr/09Off

Waking the Baby Mammoth – a Tale of Science Bringing the Past to Life

Waking the Baby Mammoth

Waking the Baby Mammoth (Yuri to the far right)

"Only a handful have ever been found before. But none like her. Her name is Lyuba. A 1-month-old baby mammoth, she walked the tundra about 40,000 years ago and then died mysteriously. Discovered by a reindeer herder, she miraculously re-appeared on a riverbank in northwestern Siberia in 2007. She is the most perfectly preserved woolly mammoth ever discovered. And she has mesmerized the scientific world with her arrival - creating headlines across the globe. Everyone wants to know... how did she die? What can she tell us about life during the ice age and the Earth's changing climate? Will scientists be able to extract her DNA, and what secrets will it uncover?" - NGC

Waking the Baby Mammoth, a new program by the National Geographic Channel premiering Sunday, April 26th at 9PM, tells the tale of a single accidental discovery of a frozen baby mammoth in the Siberian tundra and how this discovery has enriched our understanding of these extinct magnificent beasts. (My quick review: 5 stars. watch it! it's beautiful and fascinating.)

However, this is not a standard paleontological nature show about mammoths in general or what life was like during the Pleistocene. Nor is this program purely about the science behind this bountiful discovery, though the arduous nature and reality of the scientific process is certainly one of the show's stars. In fact, one of the most fascinating aspects of this program is its focus on the one man and his strange culture (from an American perspective) that led to the discovery of one of the most important findings in mammoth biology. Waking the Baby Mammoth is as much an education on the hardy nature, harsh lifestyle, and animist beliefs of the reindeer herding Nemets nomads of Siberia as it is a show about the mammoth.

Without spilling too many details, the show begins with the incredibly fortuitous discovery of Lyuba, a 40,000 year old mammoth calf, by the nomadic Yuri Khudi (and his sons), a man whose animism dictates that disturbing the remains of the dead will lead to a curse. Too often with such paleontological findings as this, the preserved creature would be dug up and put on the market, leading to irreversible decomposition and the loss of a treasure trove of valuable information. However, Yuri had enough understanding and foresight to contact authorities in Russia, which began the intensive examination and retrieval of Lyuba (including a short drama during which Lyuba disappeared due to thievery). It is implied though not fully explained that Yuri had some inkling of what he had found - in fact he believed that the corpse had been put in his path for a reason, though he dared not disturb it himself.

The program subsequently follows a very well-done modern scientific storyline, detailing the scientific process and hurdles in understanding from whence Lyuba came, how she died, and what she can tell us about her Pleistocene life. That being said, apart from specific experiments involving high tech C-T scans, internal tissue extraction via some remarkable endoscopy, and dental examinations, the program does not delve overly deep into the intricate data. It's impossible to watch the work on Lyuba without feeling the anxiety the researchers must have felt in getting everything done right the first time on so precious a specimen.

From my own scientist perspective, I think the program goes as deep as it needed to portray the scientific importance of Lyuba's discovery. More importantly, the show succeeded best at precisely what it is intended to do: to bring drama and a deep emotional human connection to a quite amazing story. Throughout the program, we are presented with many truly stunning 3D animations of Lyuba and her mother. In cinematic form fitting with the story's message, Lyuba has been brought to life as an active furry baby mammoth tromping along next to researchers as they contemplate the frozen carcass' secrets. The visuals are beautiful, as the light shines off the baby's fur at just the right angles and her shadows dance in just the right way to really make her come alive - like a corporeal ghost watching her own ancient body bring her back to life in our own minds. Some of the more touching scenes involve Yuri himself near the end.  A full year after his initial discovery, he was finally given the chance to suit up in aseptic surgical gear and join the researchers in the lab to witness first hand what his discovery meant to the rest of the world so foreign to him. It's hard to imagine what must have been going through this relatively "simple" man's mind, but his own expressions make it clear that he had come to understand the importance of his discovery and its impact as a blessing - not a curse - on our understanding of life's history. In his final farewell we see him and the animated Lyuba together in a quite touching cinematic juxtaposition of this nomadic reindeer herder and his now eternal connection to baby Lyuba.

Waking the Baby Mammoth is a tale that depicts the contrasting of cultures, worldviews, and personal beliefs of humanity amidst the backdrop of a seminal scientific discovery. Where this program succeeds remarkably well is in making the viewer understand the integral importance of these disparate cultures and the fortuitous convergence of good fortunes that allowed Lyuba to give us a new view of a lifeform long lost to us.

It is in this sense that NatGeo has truly woken the baby mammoth and placed her firmly within our modern human minds and hearts.

Be sure to check it out on the National Geographic Channel on Sunday, April 26th at 9PM. Lyuba will also grace the cover of the May edition of National Geographic Magazine on newstands April 28th.

Christie over at Observations of a Nerd also has a glowing review up now.

Once again I'd like to thank Minjae Ormes (Digital PR Consultant for NatGeo) for 1) the opportunity to review the NGC programs and 2) for being so cool in our communications.

If your interested, also check out my recent review of NatGeo's Kingdom of the Blue Whale.

The National Geographic Press Release

A MAMMOTH SURPRISE.

NATIONAL GEOGRAPHIC CHANNEL'S WAKING THE BABY MAMMOTH FOLLOWS A GLOBAL FORENSIC INVESTIGATION INTO THE LIFE AND DEATH OF THE BEST-PRESERVED BABY MAMMOTH EVER DISCOVERED

Scientists Embark on a Paleo-Detective Expedition to Reveal the Secrets of this 40,000-Year-Old Phenomenon, as Centuries-Old Indigenous Culture Meets Modern-Day Science

"This baby looks like you could snap your fingers and she would wake up and walk."

Narrated by Award-Winning Actor Victor Garber,
Waking the Baby Mammoth
Premieres Sunday, April 26, 2009 at 9 p.m. ET/PT

(WASHINGTON, D.C. - APRIL 1, 2009) Only a handful have ever been found before.  But none like her.  Her name is Lyuba.  A 1-month-old baby mammoth, she walked the tundra about 40,000 years ago and then died mysteriously.  Discovered by a reindeer herder, she miraculously re-appeared on a riverbank in northwestern Siberia in 2007.  She is the most perfectly preserved woolly mammoth ever discovered.  And she has mesmerized the scientific world with her arrival - creating headlines across the globe.  Everyone wants to know ... how did she die?  What can she tell us about life during the ice age and the Earth's changing climate?  Will scientists be able to extract her DNA, and what secrets will it uncover?

Now, from behind the headlines, National Geographic Channel's (NGC) Waking the Baby Mammoth sets out around the world on a cutting-edge forensic investigation into Lyuba's life and death, 10,000 years after most populations of her species became extinct.  Narrated by award-winning actor Victor Garber, the two-hour special premiering Sunday, April 26, 2009 at 9 p.m. ET/PT tells Lyuba's incredible story with insight from her indigenous Siberian rescuers and the scientific community so captivated by her, as a centuries-old nomadic tribe meets modern-day science in this fascinating cultural exchange.  The discovery of this baby mammoth gives researchers their best chance yet to build a genetic map of a species that vanished at the end of the last ice age.  Through her DNA, Lyuba could finally explain why the prehistoric giants were driven to extinction, share clues about their migrations, and perhaps shed light on climate change.  Could she even some day help to resurrect mammoths?  With research funded in part by the National Geographic Society, Lyuba's journey will also be the May cover story of National Geographic magazine.

Filmed on three continents, Waking the Baby Mammoth presents a 21st century paleo-detective expedition that takes viewers from the tundra of remote Siberia to cities in Japan, Europe and North America as we join a nomad and leading scientists to "awaken" this startlingly lifelike baby.  We travel back to the ice age with Lyuba via CGI animation and then fast-forward to the present to reveal the latest innovations in woolly mammoth research, including advanced computed tomography (CT) scanning and DNA analysis, searching for clues to her species' life, extinction and scientific future.

Waking the Baby Mammoth first follows paleontologist Dan Fisher and mammoth "hunter" Bernard Buigues back to the spot where Lyuba was discovered in May 2007.  She was found on a snowy riverbank by Yuri Khudi, a nomadic reindeer herder in Russia's remote arctic Yamal-Nenets region.  Named after Yuri's wife, Lyuba was turned over to the scientists at the Salekhard Museum in Siberia, which is where the next chapter in her journey began.

The film next accompanies Lyuba to Japan's Jikei University School of Medicine, where her body undergoes three-dimensional computer mapping that produces detailed images of her internal organs and structure, providing scientists with insight into the possible cause of her death.  With all but her tail and woolly coat of fur, the CT scans showed that the 200-pound baby was in excellent health when she died, with healthy fat tissue and no damage to her skeleton.  The scientists conclude that Lyuba met her end by drowning or falling into deep mud, as there are large amounts of sediment packed into her trunk, mouth and trachea.  They believe that her final muddy resting place became part of the region's permafrost, preventing decay and keeping her remarkably intact, down to her perfect trunk and largely unblemished skin.

Researchers have long debated whether woolly mammoths' extinction was due to climate change or overhunting by humans.  Now they hope to compare her DNA with that of other mammoths from the ice age to trace the migrations of mammoth populations over time and help solve the mystery of her species' disappearance.

Finally we travel with Lyuba to the Zoological Institute in Saint Petersburg, Russia, to follow the scientists as they conduct an autopsy and analyze her tissue, bone and teeth to reveal insight into the structure of mammoth organs and muscles.  Their study is able to confirm Lyuba's age, her diet, the season of her death and environmental conditions for her mammoth herd in Siberia during her short life.  In fact, they are even able to extract pollen that remained in her lungs, which can be used to reconstruct prehistoric plants that grew on the site where Lyuba died.  The bone and tissue samples that are collected will also be used for future DNA analysis and shared among mammoth research teams worldwide, so experts across the globe can learn from her.

For mammoth scientists, discoveries like this truly come once in a lifetime.  As Alexei Tikhonov of the Russian Academy of Science says, "Lyuba is a creature straight out of a fairy tale.  When you look at her, it's hard to understand how she could have stayed in such good condition for 40,000 years ... This is the most amazing discovery since we've been studying mammoths."

For more information on the best-preserved baby mammoth ever discovered, visit natgeotv.com/mammoth beginning in early April 2009.

Waking the Baby Mammoth is produced by Woollyworks, Inc.  Producer is Adrienne Ciuffo and director is Pierre Stine. Special thanks to The International Mammoth Committee.  For National Geographic Channel, executive producer is Chris Valentini; senior vice president of special programming is Michael Cascio and executive vice president of content is Steve Burns.

National Geographic Channel

Based at the National Geographic Society headquarters in Washington, D.C., the National Geographic Channel (NGC) is a joint venture between National Geographic Ventures (NGV) and Fox Cable Networks (FCN).  Since launching in January 2001, NGC initially earned some of the fastest distribution growth in the history of cable and more recently the fastest ratings growth in television.  The network celebrated its fifth anniversary January 2006 with the launch of NGC HD which provides the spectacular imagery that National Geographic is known for in stunning high-definition.  NGC has carriage with all of the nation's major cable and satellite television providers, making it currently available to nearly 70 million homes.  For more information, please visit www.natgeotv.com.

MEDIA CONTACTS:

Russell Howard, National Geographic Channel, 202-912-6652, RHoward@natgeochannel.com

Chris Albert, National Geographic Channel, 202-912-6526, CAlbert@natgeochannel.com

National Broadcast: Dara Klatt, 202-912-6720, Dara.Klatt@natgeochannel.com

National & Local Radio: Johanna Ramos Boyer, 703-646-5137, Johanna@jrbcomm.com

National Print: Christie Parell, The Fratelli Group, 202-822-9491, CParell@fratelli.com

Local Print: Licet Ariza, The Fratelli Group, 202-496-2126, LAriza@fratelli.com

Digital: Minjae Ormes, Independent Digital Consultant, 917-539-7646, Minjae.ormes@gmail.com

Photos: Christine Elasigue, National Geographic Channel, 202-912-6708, celasigu@ngs.org

25Mar/09Off

Adaptation of the Week – Channichthyidae Icefish Blood and Antifreeze

I owe the following example of evolutionary adaptation to the always amazing evolutionary and developmental biologist Dr. Sean B. Carroll, from his lecture "Making of the Fittest" for the Darwin College - Darwin Lecture Series, available at iTunes U (I highly recommend everyone give it a listen).

The Red Blood Cell-less Icefish © Dr Julian Gutt and Alfred Wegener Institute

The Red Blood Cell-less Icefish © Dr Julian Gutt and Alfred Wegener Institute

Imagine that you are a fish - exothermic and thus unable to regulate your own body temperature - and the contingent foibles of natural history have all conspired to leave you and your kind in the frigid oceans of the Antarctic just as they are beginning to reach the freezing point (10-14 million years ago).

You like the cold and are well adapted for it, but these temperatures are beginning to give even you - a master of the cold - the icthy chills.

Now imagine that the hands of mother nature have given you the tools to change your own genetic code, and thus your nature, allowing you to make yourself even more suited for waters that are 2 degrees celsius below the freezing point of pure water.

What would you do? Would you inject your DNA with a molecular antifreeze? That seems like a reasonable addition - one we will get to momentarily.

But if you were a genius of bioengineering would you reach out a molecular scalpel and hack away the genes that allow the production of red blood cells, hemoglobin, and myoglobin, leaving only molecular fossils behind?

Icefish Larva

Icefish Larva © Uwe Kils

It doesn't seem like a particularly well thought out plan. But then again, neither you, the fish, nor mother nature are genius bioengineers. Fortunately for life, the forces of evolution still manage to get the job done, however sloppy the end results (yes, technically the job is never done - forgive my metaphor wearing thin).

In fact, natural selection performed just such a feat somewhere around 8.5 million years ago in the ancestors of a flock of related species in the Antarctic: the Channichthyidae icefishes (also known as crocodile icefishes or white-blooded fishes).

As we all know, liquids tend to become more viscous in the cold. Just compare maple syrup before and after refrigeration. Blood viscosity would have no doubt been an issue in the ancient ice fish ancestors, or at least one that could be improved upon. Normal vertebrate blood is filled with big, round, and red blood cells coursing through the blood vessels. Now imagine lowering the temperature of the blood below the normal freezing point of water - that's bound to create some significant resistance.

But aren't erythrocytes critical for carrying oxygen? How could an organism just dispense with them completely? As many scientists know, one of the great things about really cold water is that it can be packed with oxygen. Such is the case with the waters of the Southern Ocean, which are saturated with oxygen.

Thus, it seems that at some point, the icefish ancestors developed mutations in the pathways that result in red blood cell production. Furthermore, the species eventually acquired a deletion in the key genes of red blood cells: the alpha and beta hemoglobin genes. No longer could this fish produce hemoglobin.

As is often the case with evolution through loss of gene function, the deletion wasn't perfect. Almost all vertebrates have both hemoglobin genes lying next to each other within the genome. In most Channichthyidae icefishes, the beta hemoglobin gene has been completely deleted, along with all but the truncated end of the alpha hemoglobin gene (interestingly, these fish have lost their myoglobin gene as well)1. To quote the original paper by Near et al.:

"Despite the costs associated with loss of hemoglobin and myoglobin in icefishes, the chronically cold and oxygen-saturated waters of the Southern Ocean provided an environment in which vertebrate species could flourish without oxygen-binding proteins."

The upshot of all this is that the icefish has completely clear blood lacking in any erythrocytes - and they are the only species of vertebrates to have such a trait.

Normal 2 globin genes vs. lost icefish globins - modified from Near et al 2006

Normal two hemoglobin genes vs. lost icefish hemoglobins - cropped figure from Near et al 2006

Of course, a few other supporting traits evolved as well. Their hearts are significantly larger than other fish hearts, and they pump 4 to 5 times larger volume of blood per stroke2. Their capillary beds have become much more dense as well to make sure all their tissues get adequate oxygenation. Of course, like amphibians that breathe through their skin, with the loss of red blood cells, those that were better able to absorb oxygen tended to outperform their cohorts. Thus they became scaleless as well.

As if these adaptive feats weren't cool enough (pun intended), the antarctic icefishes have evolved their own antifreeze as well3,4. What's amazing about this antifreeze (an Antifreeze Glycoprotein - or "AFGP") is that it represents one clear cut case in which a gene with a specific function has evolved into a separate gene used for a completely different function in a novel way. In the case of the icefish, the ancestral gene was a trypsinogen (a pancreatic digestive enzyme), which has been mutated and co-opted to be secreted and distributed throughout the body to act as an antifreeze. Specifically (for you biologists out there), the 5' secretory signal and 3' UTR sequences of trypsinogen were tacked onto an amplified nine nucleotide sequence from within the trypsinogen precursor to create the novel antifreeze peptide.

So here we have in the icefish's adaptation to the cold, at least one case of de novo creation of a novel gene with a new function from an old gene, as well as the loss of two other genes that have left genomic fossils behind to whither in the weathers of time.

It may not be the cleanest or best engineered solution to the problem of living in an Antarctic Hell (or perhaps Heaven from the perspective of the fish), but this messiness of evolution is precisely what makes it so incredibly beautiful.

References

  1. Near T.J., Parker S.K.,  Detrich H.W. A genomic fossil reveals key steps in hemoglobin loss by the Antarctic icefishes. Molecular Biology and Evolution, v.23, 2006, p. 2008 - 2016.
  2. William C. Aird. Endothelial biomedicine. Edition: illustrated. Published by Cambridge University Press, 2007
  3. Chen L., DeVries A.L., Cheng C-H. C. Evolution of antifreeze glycoprotein gene from a trypsinogen gene in Antarctic notothenioid?fish. PNAS, April 15, 1997 vol. 94 no. 8 3811-3816
  4. Chen L., DeVries A.L., Cheng C-H. C. Convergent evolution of antifreeze glycoproteins in Antarctic notothenioid fish and Arctic?cod. PNAS, April 15, 1997 vol. 94 no. 8 3817-3822
  5. Top image © Dr Julian Gutt and Alfred Wegener Institute
  6. Icefish larval image by Uwe Kils

Previous Adaptations of the Week:

  1. Timber Rattlesnake Camoflage
  2. The Aye-Aye’s Freaky Finger (I’ve Been Cursed by an Aye-Aye!)
  3. Flatfish Eyes & Recapitulation Theory
  4. Bird/Crocodile Symbiosis?
  5. Insect Dorsal Ocelli