Attending a Dissection

Whenever I think I know a lot about a subject, something happens that makes me realize how little I actually know. I had a moment like last Tuesday when I went to the American Museum of Natural History to watch William Mauck III, the ornithology-laboratory supervisor at AMNH, dissect, clean and stuff a raven before it entered the collections at the museum. Mauck normally would prepare the bird alone in the lab, but this week he did the work in front of one of AMNH’s afterschool classes and a few guests like myself.

Raven pre-dissection. Photo credit: Sandra Lewocki

Anatomy is one of my favorite subjects, and I know a little about birds, so I expected what I would see during the dissection to be familiar. Mauck skinned the raven and showed us the bird’s now skinless abdomen, and I saw what I expected - large pectoral muscles and some fat stored in the clavicular region. After we all got a good look, Mauck proceeded to cut open the abdomen to get tissue samples and see what the stomach contents were.

First cuts into the raven. Photo credit: Sandra Lewocki

As he sliced open the body, all of us were shocked by what we found.

Raven being skinned. Photo credit: Sandra Lewocki

Six eggs were inside our raven! The eggs were in varying stages of development. The most developed egg had a thin shell around it while the other five did not. Since the bird had been in the freezer for so long, the eggs were hard and we got to see them clearly, which is rare. Even Mauck, who prepares birds all the time, was surprised. He said that normally you don’t see many eggs, and if you do, they tend to pop into a gooey mess right away.

The most developed egg and its shell. Photo credit: Sandra Lewocki

I knew birds laid eggs, of course, but I never thought about how that happened. Mauck explained to us that bird genitalia is completely different than that of mammals. Both male and female birds of most species reproduce, urinate, defecate, and, if female, lay eggs through the same opening called the cloaca.

During mating season, the cloaca swells, and male birds temporarily store sperm in their cloaca. While bird courtship is notoriously long and involved, actual intercourse is short, taking about a minute. During mating, the male bird balances on top of the female, who moves her tail out of the way, allowing the male to briefly touch his sperm-saturated cloaca to hers, just long enough for sperm transfer. (Aquatic bird anatomy and intercourse is slightly different.) The sperm enter the female’s sperm-storage tubules and will then fertilize eggs as ovulation occurs. Birds may mate several times during the season to increase chance of fertilization as only1-2% of sperm that enter the female’s cloaca make it to the sperm-storage tubules.

The raven and its eggs. Photo credit: Sandra Lewocki

Female birds only have one ovary and oviduct, usually the left one, with the exception of raptors which have two. No one knows why they have only one, but it means most birds can only lay one egg per day. Once the females have sperm to fertilize their eggs, eggs develop in an assembly line. First the newly-fertilized egg is released from a follicle of the ovary to the oviduct. In the oviduct, layers of yolk are formed to provide food for the young embryo. Then the egg goes to the isthmus where the shell membranes are formed. Once that’s done, the egg moves to the uterus where the hard calcified shell is made. Colors or patterns are also added in the uterus. Finally the egg travels out the cloaca and is laid.

Egg development in the body is extremely fast, taking about 24 hours per egg. Most of the embryotic development happens outside the mother’s body, after the egg is laid. Laying eggs rather than carrying their young inside the mother’s body works well for birds since it keeps the mother from becoming too weighed down to fly.

Diagram by blog author

The raven we dissected in the AMNH classroom had one large egg with a thin shell and several eggs in earlier stages of development without shells. The raven died at a bird rehab facility near Berkeley, California of a broken wing before it could lay the eggs. The bird’s life ended, but the dissection doesn’t mark the end of the story or the end of our study - the skin and tissue samples will be kept at AMNH for researchers to learn from, both now and in the future.

Book Review: Six Easy Pieces

Author's own image.

As much as I enjoy science I’ll admit when I first started trying to decipher my physics textbook I was pretty discouraged. Instead of finding myself intrigued by how physics explains the world around us, I was confused by complicated formulas, or caught up in the busy-work of adding vector quantities.

Why should I care about physics anyway? I wanted to understand the point of these formulas, but my textbook didn’t help me. I put it aside for a while and picked up a smaller book, Six Easy Pieces by Richard P. Feynman. When I started reading the first chapter, I was relived. There wasn’t any jargon or complex equations, just the central ideas of physics explained in a way that I could understand. Even though the title of Feynman’s book is Six Easy Pieces, it wasn’t easy in a dumbed down sort of way. This book made me think, or maybe I should say it allowed me to think, since the way Feynman explained physics gave me the information I needed to begin to understand how the laws of physics influence our world.

Feynman wrote about physics like they were the most fascinating thing in the world. I caught some of his enthusiasm myself. Now that I understand why the formulas I struggled with are useful, I’m ready to go back to them. Learning anything is much easier if it’s intriguing and understandable.

Here are a few things I learned from Six Easy Pieces that made me think.

• All other scientific disciplines can fundamentally be explained by physics.
•  We don’t really know what energy is, even though we defined multiple types of energy and came up with properties of energy
•  Gravity doesn’t really pull objects downward, it just pulls them away from the straight path they would travel on if unimpeded.
• Particles on a small scale (like electrons and protons) move in strange ways that are hard to make sense of since we’re so used to “normal” large-scale motion. However, familiar large-scale motion only acts the way it does thanks to the unfamiliar motion of small-scale particles.
• Quantum mechanics (a division of physics devoted to studying the motion of atomic and sub-atomic particles) only makes sense if uncertainty is involved. What we don’t know is what makes quantum mechanics make sense.
•  Particles and waves on a large scale move in obviously different ways. But, on a small scale what we thought were particles (like electrons) end up to work like waves and what we thought we waves (like light) end up to work like particles. Everything in the subatomic world becomes a sort of mixture of particle-like and wave-like qualities.

If you are interested in physics, but don’t want with jargon and equations, Six Easy Pieces is a great book to read.

I’m always on the lookout for science books that are interesting to read. If you have any recommendations please let me know!

We Need Bacteria

Food allergies are on the rise. If we can eradicate smallpox, why are people becoming fatally ill when exposed to food that’s supposed to be good for them? Are we forgetting about some vital aspect of human health?

I learned from Dr. Jack Gilbert at the American Museum of Natural History’s Teen SciCafe, that yes we are neglecting an important aspect of human health.

Well, it’s not exactly human health that we’re forgetting about but the health of the millions of microbes that cover our skin and inhabit every organ of our bodies except the brain. Yes, bacteria are everywhere, and yes they are good for us.

Peanut butter toast and milk, standard snack or a potential hazard?

In our society we are taught that bacteria are bad and we must kill them with soap. While this is true about some bacteria, there are many other microbes that we need to survive.

 Dr. Jack Gilbert and his colleagues have studied differences in sterile mice (mice never exposed to any bacteria) and normal mice (teeming with bacteria). They found sterile mice’s organs wouldn’t develop properly, they had no fight or flight response to stressful situations, and these mice had severe food allergies. When these sterile mice were treated with good bacteria, they regained their fight or flight response and became tolerant of foods that once poisoned them.

Bacteria are amazing, they’ve been on earth for 3.8 billion years, far longer than we have. We evolved to live with and depend on bacteria. Each of us have our own unique microbe colony which influences many bodily functions from weight gain, to food tolerance, to mental health.

Okay, now we know there’s a link between bacteria and health, now what do we do?

Can we use our knowledge to help decrease risk of food allergies? According to Dr. Gilbert the answer is yes, but we might have to change the way the medical field functions. The nature of our modern, western, medical field is one-size-fits-all. We want easy treatments that work the same way on everyone. But, everyone has a unique microbe colony. Treatments that work for me based off my microbe colony might not work for you. Now that we can figure out people’s microbiomes and understand what they mean, it might be time to go back to personalized medicine.

Dr. Gilbert and his colleagues have worked with more personalized microbe therapy for children with food allergies by introducing butyrate-producing bacteria to their intestines. The bacteria helped the children to handle trigger foods better and reduced the severity of the children’s reactions, or even ended the reactions all together.

Bacteria aren’t the cure-all but it’s about time they get attention. At the Teen SciCafe hosted by American Museum of Natural History, microbes were put in the spotlight thanks to Dr. Gilbert’s lecture. We also got to try out a new student designed card game called Gutsy all about microbes in the gut. The card game was the perfect way to set the mood for microbe talk. Now I’m very excited about bacteria! Improving microbial health can have big impacts, such as reducing risk of food allergies, but doesn’t have to be complicated, just spending more time outdoors and eating food rich in good bacteria can improve your microbiome. (Sauerkraut anyone?)