Blood Colors

First of all, we want to wish all of our readers a Happy (and safe) Halloween! Now, onto the science of blood.

Some of the most iconic monsters of all time seem obsessed with blood. Of course, vampires are the most famous among mythical creatures, but sharks can smell blood in the water from miles away, and vultures and ravens are attracted to the smell of blood and decaying flesh on land. All animals, with the exception of some very simple invertebrate animals like jellyfish, coral, and flatworms, have blood. An average human will have between 1 and 1.5 gallons of blood in their body at any time, and blood accounts for roughly 7% of the person's weight. It's an essential, valuable thing.

In general, human blood is made up of four major parts: white blood cells, plasma, platelets, and red blood cells. White blood cells, or leukocytes (luke-o-cites), are part of your body's immune system, and they are responsible for responding to microscopic threats that your body faces from bacteria, parasites, and infections. Platelets, or thrombocytes, are the small cells that stick together to form scabs and stop vessels from bleeding. They are the reason why all your blood doesn't spill out when you get a cut! Plasma is the colorless liquid that the other components are suspended in, and is mostly made of water.

Red blood cells, photographed with a scanning electron
microscope. Photo by the Wellcome Trust/Marc Turner.

Red blood cells are also called erythrocytes (air-ith-throw-cites), and they give blood its red color. Their job is to carry oxygen to every cell in your body. The cells then use the oxygen to create food and energy. The red blood cells also take waste away from the cells. As the red blood cells pass through organs like the liver and the kidneys, the waste is filtered out and eventually expelled from the body. Red blood cells are born in a person's bone marrow, and every cell will live roughly 120 days (about 4 months). Once they die, the spleen filters them out. The spleen also removes any red blood cells that are misshapen or damaged.

Of course, the color most associated with blood is red (I mean, it's right there in the name of the cells!). But blood actually comes in a rainbow of different colors, and it all has to do with the types of chemicals that it contains. Most vertebrates (animals with backbones) have red blood because our red blood cells contain hemoglobin, an iron-based protein. Each hemoglobin protein is made up of individual hemes, which bind iron particles. The iron particles in turn bind oxygen, which is then carried to the rest of the body. A deficiency in iron is called anemia, and is actually a fairly common deficiency in America. Since a low iron level makes it harder for blood to carry oxygen to cells, a person with anemia may become tired and short of breath more easily than someone with higher iron levels.

The different colors of blood. Image by Compound Chem.

Red blood is just one color though. Animals like horseshoe crabs have blue blood because instead of hemoglobin, they carry a protein called hemocyanin. This protein contains copper in place of iron, but it functions in much the same way. When hemocyanin-rich blood is carrying no oxygen, it is actually colorless! These animals have evolved a different type of blood circulation system that doesn't require as high of an efficiency rate, so copper sufficed.

Green blood is also seen in nature, but almost exclusively in worms and leeches. The protein that makes blood green is called chlorocruorin. Chlorocruorin also contains iron in its center, but one branch of the protein is replaced with a different chemical structure, which alters the entire protein. There is one lizard, aptly called the green-blooded skink, whose blood is indeed green. This lizard actually has true hemoglobin in its blood, but when its cells die, its body cannot break the protein down as far as our bodies can. The result is that the lizard's blood has a higher concentration of a by-product called biliverdin, which gives the lizard's blood a green color.

The green-blooded skink. Photo by Christopher Austin,
Louisiana State University Museum of Natural Science

One last shade of blood is bright violet-pink, which is the rarest color of all, occurring only in some species of marine worms. This blood's color is from a protein called hemerythrin, which is made of individual chemical units which all contain iron. This protein can only carry about 25% of the oxygen that hemoglobin could carry, unfortunately for the worms!

As much as modern science has learned about blood over centuries of study, the one thing no one can yet do is manufacture blood. Since blood is such a vital resource, and because it cannot be created, the only source of blood for people is other people. This is why blood drives are so necessary for people suffering from diseases or recovering from major accidents. If you are able and willing, please try to donate blood soon. Perhaps you can even make a joke about how the blood drive workers just wanted to suck out your blood!

Sources:
http://science.sciencemag.org/content/192/4237/335
https://www.compoundchem.com/2014/10/28/coloursofblood/
http://scienceline.ucsb.edu/getkey.php?key=2419
http://idahoptv.org/sciencetrek/topics/blood/facts.cfm
http://www.chp.edu/our-services/transplant/liver/education/organs/spleen-information

Fear of the Dark

Imagine a scary setting. Whatever kind of environment would make the hair on the back of your neck stand up straight and give you the feeling that someone–or something–is watching you, imagine it. I'll make a bet that the majority of these scenes are set sometime during the night. And why not? To some extent, everyone has a fear of the dark. Nyctophobia, or a deep and severe fear of the dark, is one of the more common phobias in humans. Where does this fear come from?

There is a lot of evidence to suggest that a fear of the dark is deeply rooted in our evolutionary history. 4.5 million years ago, the early ancestors of Homo sapiens were not the masters of the planet like the species is today. Instead, animals like Australopithecus afarensis were prey for bigger, stronger, faster animals. One advantage our ancestors had were that they were social animals, relying on each other to watch out for danger. This was an effective strategy, but only during the day. At night, their vision failed them. That meant they were vulnerable to attack. Truly, it was never a fear of the darkness itself, but the dangers the darkness concealed that fueled fear. The advent of anthropogenic fire certainly helped protect and defend us, but only if one stayed close to the flames. Eventually hominids started to build shelters, which added another layer of protection from both the elements and the predators.

The Tsavo Lions exhibit at the Field Museum in Chicago, IL
Photo credit: Jeffrey Jung

Even today, in areas where lions and humans live near each other, the risk of of a human being attacked by a lion is roughly 60% higher after 6 pm, according to a study published in 2011. This is partially due to the fact that lions generally hunt at night; the reasons for this are a combination of lower temperatures and an inherent advantage that predators have over their prey. One of the most vicious and notorious lion attacks were those committed by the Tsavo Lions, who preyed on the workers of the Kenya-Uganda Railway in 1898. These two lions were bold and their attack style was unprecedented: they would come into camp at night and drag workers from inside their tents. Any attempts to stop the lions from entering the camp with fire or fencing were thwarted by the lions. Workers left the construction site in large numbers and all progress on the railroad halted until British Lt. Col. John Henry Patterson hunted and killed both of the lions in December 1898.

The movie poster for the 1996 film about the
Tsavo Lion attacks in Tsavo, Kenya.

After their deaths, the legend of the Tsavo Man-Eaters grew. Patterson took their skins and made them into floor rugs, as was the style of the time. In 1924, the rugs were sold to the Field Museum of National History in Chicago, IL for a sum of $5000 (about $73,400 in today's money). The skins were in poor condition from a quarter century of being walked on, but now the skins and the skulls of the lions are on display in the lower level of the Field Museum. Isotopic analysis of the keratin in the bones and hair suggest that one lion ate the equivalent of 10.5 humans, and the other ate the equivalent of 24.2 humans. From Patterson's personal journals, the Tsavo lions killed between 28 and 31 people. The discrepancy in the numbers may reflect people the animals are known to have killed, but not necessarily eaten. The story of the Tsavo Lions continues today in modern entertainment, and appears in video games, movies, and books. My favorite is The Ghost and the Darkness, a 1996 movie starring Val Kilmer as Patterson.

What makes lions so adept at hunting at night? One of the many tools available to lions is their night vision. Cats need just 1/6th of the light humans need to see, giving them a significant advantage in low-light environments. Their eyes are also better at focusing that light more effectively than ours are. The curved cornea and large lens allow the cat eyes to take in all available light, and they also have a higher number of rods that are sensitive to dim light in their eyes than humans do. Cats also have a special layer in their eyes that hominids lack, called the tapetum, which directs light to sensory cells that bathes the retina in 50% more of the available light than the cells would receive otherwise. While a cat cannot see in fine detail or in as many colors as we can see, their eyes are designed to hunt, particularly at night. It's no wonder that cats are likely apex predators in their habitats, considering this and all their other tools!

Eye structure and function in cats by K. N. Gelatt,
seen in Merck Veterinary Manual.

The night is not just a place where scary things hide; it can hold discovery as well. It is needed to study distant stars and to see the Milky Way from Earth's surface. It is also associated with rest, sleep, and safety, a time when families gather in their homes and prepare for the next day. With all the artificial light available to humans now, true darkness can be hard to find, at least in the United States. Light pollution is a problem that affects migrating animals and can affect a human's ability to sleep soundly. Minimizing the disruption to our bodies' rhythms is why companies like Apple have "night modes" for their technological products. I myself have a rule that I am not allowed to look at my phone or computer screens after 9:30 pm, or else I sleep poorly and can hardly think the next day.

Perhaps the lesson here is that everything, even light, has a dark side. That nervousness I feel walking alone at night is just a normal evolutionary response that served my ancestors well, but it never stopped me from Trick-or-Treating after sunset when I was younger. There are still dangers in the dark, of course, but at least they are (probably) not lions anymore!

Sources:
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0022285
https://www.sciencedirect.com/science/article/pii/S0149763410001399 
Kerbis Peterhans, J. C. & Gnoske, T. P. (2001). "The science of 'man-eating' among lions Panthera leo with a reconstruction of the natural history of the 'man-eaters of Tsavo'". Journal of East African Natural History. 90 (1): 1–40.
http://www.pnas.org/content/106/45/19040
The Man-Eaters of Tsavo and other East African Adventures by Lieut.-Col. J. H. Patterson

Cryptozoology

Now that it is most definitely October, we thought it'd be fun to talk about the science behind some of the classic horror stories associated with Halloween, and about some animals that are generally associated with the spooky, occult, or unknown. Until Halloween, we'll be focusing on these topics to help get everyone into the spirit! Our first topic is the study of hidden monsters: cryptozoology.

Cryptozoology is the name for the field that focuses on finding cryptids, or animals that, so far, only exist in folklore and oral traditions. Some examples of these unknown animals are Bigfoot (or Yeti in the Himalayas); Nessie, the Loch Ness Monster in Scotland; and the chupacabra of Mexico and the southwestern U.S. states, but it turns out there are hundreds of creatures that fit into the cryptid category. Because it does not follow the scientific method, a process where hypotheses are proposed, evidence is collected and analyzed, and conclusions are drawn that either reject or support the hypotheses, cryptozoology is considered a pseudoscience, halfway between zoology and the branch of cultural anthropology that focuses on folklore and legend.

A map showing some of the cryptids of American folklore and oral tradition.
From: https://www.hogislandpress.com/product/monster-map

I first heard of some of the animals in the graphic above from a television show that aired on Animal Planet. I used to wake up very early before school started, which meant my options for TV shows were limited. Animal Planet always had something on though, and for a while one of the shows I watched was Lost Tapes. Every episode focused on a different cryptid's story, going through the original folklore in between flashbacks from "lost tapes" that show a victim's interaction with one of the fearsome, mysterious animals. Every story was fictional, but some were done so well and were so unnerving that I think about them to this day.

The show only lasted for 34 episodes, unfortunately, and exposed its audience to monsters such as the Thunderbird, Wendigo, Hellhound, and the Jersey Devil. The descriptions of these animals and the legends behind them can be skin-crawling, and I think the show did an excellent job of presenting the monsters in a way consistent with the right levels of reverence and fear. I personally enjoyed learning about the history of the legends more so than seeing the flashback parts of the episodes, but sometimes they'd also share information about recent possible sightings of the animals. It always made me want to go out and try to find something on my own.

Luckily Animal Planet has another show about hunting a cryptid that I can watch instead of camping all over the country (even though I'll probably do that on my own anyway). This show is, of course, Finding Bigfoot. On the show a small team of Bigfoot enthusiasts go to towns where Bigfoot sightings have occurred and then attempt to have their own encounters. This team takes their work seriously, even though there is no concrete physical evidence of any kind of large ape living undetected in the continental U.S. and Canada. The team meet with local people who have stories to share, and then the team goes out into the area where the sightings occurred to recreate the encounter. They do this to figure out what kind of animal could fit the description the witness gives. A majority of the time, the team actually rules out Bigfoot as the culprit for an unusual sound at night or a quick glimpse in the woods, and instead attributes the encounter to a bear, elk, or deer.

The team also spend time walking around the woods at night, making Bigfoot calls and knocking on sticks as Bigfoot is thought to do. They use thermal imaging and night vision goggles to heighten their sense of sight and maximize any chance of seeing a Bigfoot. Their ultimate goal is to find definitive proof that Bigfoot exists, and the show exists to document their adventures. The probability that a large, bipedal primate (aka Bigfoot) has consistently escaped any kind of detection by modern humans is very small, but non-zero. This uncertainty fuels their curiosity and drives them to keep looking.

Model of Latimeria chalumnae in the Oxford Univ. Museum of Natural History.
Photo by: Ballista at the English Language Wikipedia

While it is unlikely that anyone will ever find hard evidence of Bigfoot's existence, it is important to acknowledge that there are still many things that science cannot answer. Wildlife biologists discover new species every year, and while the vast majority are new insects, invertebrates, and amphibians, sometimes a new mammalian or even primate species is found. Sometimes animals thought to be extinct reappear in the modern day; for decades, paleontologists thought the ceolacanth fish extinct since the Cretaceous, until one was caught off the east coast of South Africa on December 23, 1938. It was Marjorie Courtenay-Latimer, curator at the East London Museum, who recognized the unusual fish in the catch of a local fishing captain, and brought it to the world's attention. Today, there are coelacanths in museums around the world.

Any scientist needs to walk a razor's edge between keeping an open mind to all possibilities while carefully and critically examine all the evidence in front of them to find the best answer. Often this means that there are far more likely explanations for something than "Bigfoot did it," hence why the existence of these animals isn't in any way guaranteed. What is fascinating to me is seeing all the ways that humans have explained nature around them and passed stories down through the centuries, and how they have spread across cultures. It also reminds me that there is much left in our world to discover and investigate, some of it fairly nearby! I'd love to get a story about the Mogollon Monster this weekend when I go hiking. I guess you'll have to wait for next week's blog article to find out what happens!

Sources:
https://en.wikipedia.org/wiki/Lost_Tapes
http://aplostapes.wikia.com/wiki/Lost_Tapes_Wiki
https://www.animalplanet.com/tv-shows/finding-bigfoot/
http://www.dinofish.com/discoa.htm

The Nautilus Mission

The bottom of the ocean is one of the most unknown places on Earth. Deep canyons and high seamounts dominate the landscape. There are black smokers, small vents in Earth's crust, spewing hot water and toxic chemicals into the water. There is no plant life; sunlight cannot penetrate water that deep. The animals that live down there come in odd, pliable shapes, and some use their own bioluminescence to lure prey in. Even though it is on the same planet, the deep ocean is not of this world.

The Papahānaumokuākea Marine National Monument.
From: https://www.papahanaumokuakea.gov/

It is because it is so unknown that marine scientists are so eager to explore it, and one current mission is doing just that. The Nautilus Expedition is a massive effort to characterize and study the geology, biology, and archaeology of a few key areas of the Pacific Ocean between Hawaii, California, and Alaska. Currently, the ship is west of Hawaii, in the Papahānaumokuākea Marine National Monument (MNM), the largest marine conservation area in the world. The mission is operated by the Ocean Exploration Trust, a non-profit organization founded in 2008 to engage in pure ocean exploration. Its founder, Dr. Robert Ballard, is the man is credited with discovering the remains of the ill-fated Titanic, and is current a National Geographic Explorer in Residence. If something is going to be discovered, this is the team to do it.

So what are they looking for? For one, they are now looking closely at the underwater geology around tectonic plate boundaries, and the western coast of North America is an excellent place to do it. Multiple tectonic boundaries, including the Cascandia fault line of the subducting Juan de Fuca plate, are responsible for creating the landscape of the west coast. The Nautilus is there to photograph and map areas of the seafloor that have been missed by previous studies, and to measure the chemicals in the ecosystem around it.

Dr. Marc Fries examines this fragment of fusion crust that
may have come from a meteorite that fell in March 2018.
Picture by Susan Poulton, Ocean Exploration Trust.

Its trek began in Southern California, where it studied the deposits of underwater landslides caused by movement along the San Andreas fault, and traveled up to the Cascadia Margin near Washington and Oregon. As it moved from Astoria, WA to Sydney, British Columbia (Canada), the Nautilus also looked for fragments of a meteorite that fell in March 2018. Preliminary findings indicate that they did indeed collect two small pieces of the fusion crust that forms on meteorites as they burn up in Earth's atmosphere, and it's all because of the Nautilus mission.

The Cascadia Margin is not just of geologic interest; the large volumes of methane gas and hydrate stored in the area makes it an interesting spot for studying the chemistry of the area as well. According to the Nautilus website, "establishing a baseline by documenting and characterizing these sites is timely because geological events, such as earthquakes or submarine landslides, could result in important environmental impacts due to sudden methane release." Over the past two years of research, the Nautilus team has discovered over 2700 bubble streams at 1000 distinct locations along the Cascadia Margin. Before this mission began, it was unclear exactly how much methane was near the Cascadia fault, and how (or even if) it was being released.

As impressive as the geology and chemistry are, perhaps the most awe-inspiring is the biology discovered. At almost every location, the Nautilus stayed for at least two weeks, taking pictures and streaming live video narrated by the crew and scientists on the expedition. One of the best parts of exploring is being surprised by what is found, and this video is an excellent example of this. Taken by the Nautilus crew on September 20, 2018, this video is rare footage of an animal called the pelican (gulper) eel in Papahānaumokuākea MNM. And this was only one of the animals observed!

As it traveled to Hawaii, the Nautilus also studied multiple geologic features called seamounts, which are undersea volcanoes that have not breached the ocean's surface yet. Before the Hawaiian islands were, well, islands, they began as seamounts. Over a long period of time, the underwater volcanic eruptions built up the seamounts until they became a large island. These eruptions still happen, but because of the "hot spot" volcanic activity near Hawaii, the volcano's position is not constant. A new seamount, and future Hawaiian island, is being formed right now off the southeast coast of the large island of Hawaii. Its name is Lō'ihi, and its exploration has the potential to tell us about the habitability of other places in our solar system. From the website:

"The expedition of Lō'ihi marks the beginning of the multi-year SUBSEA (Systematic Underwater Biogeochemical Science and Exploration Analog) Research Program, a partnership between NASA, NOAA, and various academic centers. Bringing together both ocean and space exploration teams aboard E/V Nautilus, SUBSEA blends ocean exploration with ocean worlds research to address knowledge gaps related to the habitability potential of other planets in our Solar System." 

A "gripper" used for collecting samples from seamounts. This novel
tool was developed by the Jet Propulsion Laboratory, and is mounted
on the ROV Hercules, one of the robots on the Nautilus expedition.

 While it was around Lō'ihi, it documented the biological communities that live around the seamounts it observed. Because Lō'ihi is an isolated seamount (one that is not near any tectonic plate boundary), it is considered a strong analog for any kind of venting system that might exist on an ocean world like Europa, an icy moon of Jupiter. By collecting samples from fluid venting locations, geologists and biologists will be able to study the interaction between a seamount and the life that survives there. How cool is it that studying the environment around seamounts in the Pacific can tell us about potential life on other planets? 

It is impossible to put the full scope and findings of the Nautilus mission into a simple blog post, but these are just a few of the highlights that happened in the past few months. If you'd like to read more or follow along with their live-streaming, the website is here: http://www.nautiluslive.org/

Happy exploring!