Bubbles!

This week in lab, my class was supposed to play with bubbles. At first, I really had no idea how bubbles applied to developmental biology, but I later realized that it is all about balance of internal and external pressure. Bubbles of similar size will arrange themselves in certain patterns just as cells in an early embryo will. I suppose I had always thought of embryos as being very organized in this sense, but now it seems that this arrangement is determined by geometry of shapes. Each cell (bubble) adheres to the others and distributes its pressure equally to all surfaces. The following are my results:

The patterns I was attempting to make.

Pattern 1: Two Bubbles

Pattern 2: Three Bubbles

Pattern 3: Four Bubbles

Pattern 4: Five Bubbles

Pattern 5: Seven Bubbles (To Me: The Berry Berry Kix)

Pattern 6: Five Bubbles Total. Small on Top with Tiny to One Side

Pattern 7: A Bubble Progression (To Me: The Bubble Caterpillar)

Glaucus atlanticus

http://www.roboastra.com/hastslugs6/images/hpop19561.jpg

I've been hearing some recent buzz on the internet about the sea slug that looks like either a Pokemon or something out of a science fiction movie. Its name is Glaucus atlanticus, more commonly called such harmless names as the blue sea slug. Its lifestyle consists of floating about, belly-up, on the surface of the water, where it will find its formidable prey, the Portuguese Man-O-War.

I wish I could make up something this cool.

Although the Portuguese Man-O-War is famous for its painful sting, Glaucus atlanticus is not only immune to this sting, but it actually stores the poison from its prey's nematocysts (the cells that sting) and utilizes them for its own use. The poison is stored in the tips of its noodle-like extensions.

Glaucus atlanticus will use the poison to deter predators, but it also uses coloration to avoid being eaten. Like many surface-dwellers, the blue sea slug has a coloration called "countershading," meaning it is one color on one side of its body and another color on another side. We see this same technique used in dolphins, sharks, and rays. Whereas most of these creatures are darker on top and lighter on bottom, Glaucus atlanticus is darker on its belly, which is at the surface of the water. Remember that it swims upside-down at the surface. [It sounds like this is generally accepted as camouflage, but I am still uncertain. It seems to me that, when viewed from the bottom, even animals with white undersides show up dark against the water's surface. It makes me wonder if dark coloration on top is the real important factor, perhaps for both protection against the sun as well as avoiding predation from above.]

http://0.tqn.com/d/saltaquarium/1/0/O/3/
keokimanowarslug.JPG

How does one eat a Portuguese Man-O-War? According to sources that I have come across, the gut of Glaucus atlanticus may have a protective surface as well as secrete mucus which protects it from the sting. Work by Greenwood (2009) suggests that the mucus may be specific for protection against nematocysts of prey and not of non-prey species. The gut also has a chitinous tissue that the stinging nematocysts cannot break through. The chitin is present in small clumps called spindles that occupy the cells on the gut's surface. This means that Glaucus atlanticus does not actually have a layer of chitin but that the chitin is housed within the cells themselves. It's like internal armor. The nematocysts can still damage this protective layer, which may wear away, but the underlying tissues remain unharmed, and spindle-containing layer heals rapidly in preparation for the next meal.

Ehlers-Danlos Syndrome

In my previous blog posts, I have focused on varieties of animals--probably because I have always been fascinated by animals. There are also so many different animals that there is always something new to explore about them. However, considering that I plan to go to medical smedical relevance. This post will be about people.

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chool, I feel like my blog as been at a lack of, well,

When I moved to college, I met a couple friends who said they had a condition called "Ehlers-Danlos syndrome." I had no idea what that was (or how to properly spell it), but the condition left them with some interesting features. Both of them were incredibly flexible, being able to contort their fingers and shoulders in ways I would never be capable of. Even though super flexibility may sound pretty cool, it comes with its downfalls. On multiple occasions, one of my friends has twisted her knee the wrong way simply while walking down the sidewalk. I suppose it's like a snake's movable jaw; with increased flexibility comes a sacrifice to overall strength.

My friends also showed me that EDS resulted in increased skin sensitivity. One finds shaving her legs to be torturous, and the other has been known to cut himself on the most innocent of objects (from leaves flying by in a gust of wind to the hardened frosting on a cupcake). They may be more sensitive to temperature and pressure on their skin as well.

Although these are common symptoms of Ehlers-Danlos Syndrome, not all people with EDS experience the same effects, and EDS has many different types. I did some research to find out what causes this condition and why it has so many manifestations. It seems that EDS is caused by a defect in the body's collagen proteins and proteins that aid in the construction of collagen. Collagen plays a strong role in connective tissues all over the body, meaning that EDS can lead to weakened joints, difficulty in wound healing, and even weakening of the bicuspid valve in the heart. The collagen protein defects characteristic to EDS have genetic causes, and so the condition may be passed from parents to children or may even be due to spontaneous mutation. Although EDS cannot be "cured," damage to the body may be prevented. For my friends, that may simply mean avoiding a strong high-five and not rough-housing with friends.

http://upload.wikimedia.org/wikipedia/
commons/6/64/Ehlers-Danlos_Syndrome_1.jpg

Because there are many types of EDS, EDS can result from mutations in a variety of genes. I will not explore all of those here, but if you are interested in learning more about EDS, I encourage you to do a quick search on the internet. There is a lot of information out there about this intriguing condition!

Also, just to throw in a bit about animals, Ehlers-Danlos syndrome is not limited to humans. Other animals including dogs and cattle may get EDS too!

Fly Hatching

This time, I'm not going to explore some strange animal; instead, I want to share my experiences in the developmental lab. My class has been assigned to take time-lapse photographs of various developmental stages of the fruit fly Drosophila. What seemed like a simple task turned out to be a struggle that was drawn out for three weeks. Nevertheless, I finally got my data with the help of a few accidents and improvisation, but I suppose that is how all labs go.

From http://media.npr.org/assets/img/2012/12/13/istock-00000663
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I was intent on getting footage of a newly adult fly as it emerged from its pupa. The walls of the community fly jar were coated with pupae, so I figured I would have no problem. However, gently extracting the pupae from the walls--inevitably letting adult flies escape in the process--proved to be a task all of its own. I finally retrieved several pupae and arranged them neatly beneath the microscope to take a closer look. I figured it was best to have a lot of them to increase the chances that at least one would hatch in the time that I was filming. To my surprise, most of the cocoon-like structures were empty; they had already hatched!

Trying to ignore the loose flies buzzing all about the lab, I carefully gathered more pupae. I found that the darker ones were the most developed, their red eyes showing clearly through the wall of their casing. I gathered them together and set the camera, . . . only to return hours later with no results.

Between the pupae drying out and the camera not working, I found myself two weeks into my assignment and with nothing to show for it.

I tried something different. Perhaps I could catch footage of male and female flies mating. My professor told me to separate males and females for a couple days. When I reunite a male and a female, they may be so lonely that they will get straight to business. It sounded easy, so I collected some adults in a bottle, anesthetized them, and separated them out into tiny dishes--one for males, one for females. They were placed in an incubator with food and moisture. However, within a couple of hours, I found all the females on their backs with their legs wiggling in the air. After a couple days, all of my adults were dead. One dish was molding. So much for that idea.

From http://jenny.tfrec.wsu.edu/
opm/opmimages/SWDf44.jpg

I decided to try once more for the pupal hatch. This time, I reached success due to a fortunate accident: As I was arranging my unhatched pupa (this time in a dish so they could not dry out), I went to move one into just the right spot to fit into the image. My tweezers were a bit clumsy, and I wound up ripping off the front of the pupa where the fly will emerge--a part I refer to as the "hood." It came off quickly and in one piece. Shoot! I thought. That guy will certainly dry out. But, as I arranged the other pupae, I noticed that the small fly inside began to poke out of the pupa. He arched his head upward, slowly emerging. I struggled to get the camera ready, but before I knew it, the little guy was out and crawling about.

In an attempt to replicate the incident (and actually photograph it as I was supposed to), I tore the hoods off of a few more flies. Most flies must not have been ready (some still had remnants of their larval stage in back), but I did get two others to hatch on film. I have four links below. The first three are of a little fly as he struggles to hatch. He had a very difficult time emerging, and as you will see in the third video, I eventually gave him a little help. It was really interesting to see how he would shift his fluids from his abdomen so that his head would swell up and pulsate. The last video is of another fly that hatched so quickly that he was most of the way out when I began filming. All of these videos are sped up.

http://www.youtube.com/watch?v=5R3ZVzRIraw

http://www.youtube.com/watch?v=s52cHML-v9g

http://www.youtube.com/watch?v=65D9oUX0qy0

http://www.youtube.com/watch?v=8eWr898JVxs

Philtrum

Have you ever wondered about that odd groove on your upper lip? Just from a basic trivia question, I have always remembered that that groove was called the philtrum, a term that came in handy when I was taking my anatomy class. I remember learning that we had no idea what purpose it served, but a missing philtrum is a common facial feature in children suffering from fetal alcohol syndrome. You may also be familiar with cleft lip, the common developmental defect that results in a divided upper lip.

http://www.userinter.net/
wp-content/uploads/
2012/12/Medium-Lips.jpg

I am not here to specifically talk about cleft lips and fetal alcohol syndrome; I'm sure there is plenty of better reading on those topics than my blog will be. However, I came across an interesting read that may give insight as to why we have a philtrum. Even though it may not appear to have a purpose, the development of the philtrum may have been a developmental stepping stone that allows us to behave the way that we do as humans.

Let me start from the beginning. Many mammals have a groove that runs from their lip to their nose--just think of a lab rat, a dog, a cat, or a rabbit. Of course, this groove is very different from our philtrum. Their groove is more like a cut, and the two halves are not connected as our philtrum is. Hofer (1980) referred to the occurance of  such a lip as "schizocheilism," though he was specifically examining primates. It helps when I remember "schizo-" as being split or divided. The divided upper lip may give animals an edge when it comes to chemical detection, such as smelling, because the groove leaves the mouth and nose directly exposed to the environment. Although I have not found a primary source regarding this, I have also read that the groove serves as a moisture carrier, allowing capillary action to carry saliva from the mouth to wet the nose and allow for better smelling. Maybe that is why dogs have wet noses (or it could just be that they lick their noses often, and the groove may have little to do with it).

http://www.mzephotos.com/wallpapers/
mammals/rabbit-nose-1152x864.jpg

According to Hofer, the connected lip condition is called "syncheilism." This is like our philtrum; although a groove remains, the groove is connected. The outside of the groove is like the skin on our face, and the inside is just like our mouth. The mouth is not continuously exposed to the outside environment through the groove. To me, it would seem like the greater advantage lies in schizocheilism, but Hofer points out that a connected upper lip allows for greater articulation that is seen in feeling surfaces with the lips, grabbing with the lips, and articulating facial expressions. Of course, facial expressions are very central in our communication with others. Furthermore, we have all--as many primates do--felt a smooth surface with our lips because they are much more sensitive. However, I would like to note that some animals that grasp things with their lips (goats) do not have a connected upper lip. Other grazers, such as horses, have a connected upper lip. Is a connected upper lip, then, really such a big step in grasping objects?

On a different note, the philtrum is also apparently connected to Jewish lore. Although I usually prefer to quote only parts of what I read, I like this tale enough to post the whole thing. Fear not; it is short. The following is an excerpt from Gabriel's Palace: Jewish Mystical Tales by Howard Schwartz titled "The Angel of Conception":

Among the angels there is one who serves as the midwife of souls. This is Lailah, the angel of conception. When the time has come for conception Lailah seeks out a certain soul hidden in the Garden of Eden and commands it to enter the seed. The soul is always reluctant, for it still remembers the pain of being born, and it prefers to remain pure. But Lailah compels the soul to obey, and that is how new life comes into being.

While the infant grows in the womb, Lailah watches over it, reading the unborn child the history of its soul. All the while a light shines upon the head of the child, by which it sees from one end of the world to the other. And Lailah shows the child the rewards of the Garden of Eden, as well as the punishments of Gehenna. But when the time has come to be born, the angel extinguishes the light and brings fort the child into the world, and as it is brought forth, it cries. Then Lailah lightly strikes the newborn above the lip, causing it to forget all it has learned. And that is the origin of the mark, which everyone bears.

Indeed Lailah is a guardian angel who watches over us all of our days. And when the time has come to take leave of this world, it is Lailah who leads us to the World to Come.

Floppy Dog Ears

When it comes to genetics and artificial selection, domestic dog breeds are an exceptional example. We have dogs of many characteristics, which, for me, is a good thing; no dog can ever bore me with its appearance or personality because they are all so different.

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One quality that I am really curious about, though, is the flop of a dog's ears--not how ear flop may affect our ideas of a dog's "personality" but how, physiologically, some dogs' ears are floppier than others'. Most are probably familiar with the big, droopy ears of a Basset Hound while the ears of, say, a German Shepherd  generally stand erect. And then, there are dogs like my Jack Russell Terrier that have one ear erect and the other that flops midway. How can this be explained?

I dug into some research, and found conclusions that provide an answer but are not altogether satisfying. In an interesting article, Boyko et al. (2010) examined how single nucleotide changes can drastically alter a dog's phenotype. For instance, floppy ears can be seen in dogs with mutations in a small region on chromosome CFA10. Furthermore, species that are characteristically floppy-eared will tend to be homozygous for mutations in the region instead of heterozygous. However, we don't know if this is due to the selection for floppy ears or the selection of another trait that also may be affected by the same region on CFA10. CFA10 has also been associated with a dog's trainability, coat pattern, and size. I don't know exactly how these play a role in the grand scheme of the animal, but I have heard that coat color may be an indicator of potential health problems in dogs, such as a correlation between spots and impaired vision or hearing.

http://www.katherinefinkelstein.com/
files/homeimages/Dog-Ears.jpg

I am ultimately interested in finding the effects of mutations in the region of CFA10 on structure. Although I don't have the answers, my immediate thought was that, somehow, a structural protein in upright-eared dogs has been mutated in floppy-eared dogs. Thus, upright-eared dogs have ears that are more stiff. I also want to know why some dogs, such as mine, will have one floppy ear and one upright ear. How does this work? Could there be some correlation between which ear is floppy and the color pattern on that ear?

I think this is an interesting examination of cells of the same animal (therefore, having the same DNA) can have different physical appearances due to the way that the genes are expressed in the cell. Not only may ears vary from breed to breed but may also have differences within a breed and even within a single animal. Interesting stuff.

In any readers know more why dogs may have floppy ears, I would love to hear about it. The physiology underlying the genetics is something I would like to know.

The Upside of Tipsy

From http://jeb.biologists.org/
content/209/4/610/F1.large.jpg

In one of my labs a while back, we were examining metamorphosis. Of course, when I think of metamorphosis, I thought of butterflies and frogs, but one station that surprised me was the flounder. I usually don't think about fish that metamorphose, but apparently the young flounder must undergo metamorphosis to attain its sideways-looking adult form. The young flounder looks much like your average fish, with one eye on either side of the head. During metamorphosis, one eye slowly makes its way across the head to the other side of the body. As the fish changes, it slowly becomes tipped to one side until the fish is lying horizontally and the eyes are completely on one side of the head.

When I was in the lab, though, a flounder metamorphosis diagram explained that the eyes will migrate to the left side of the head. I was assuming this diagram described all flounders. However, a preserved flounder specimen was floating in a jar on the lab table, and clearly, its eyes were not on the left but the right side of its head. What, then, determines which side of the head makes the eye side of an adult flounder? Is it determined by species or does it vary with individual, much like left-handedness or right-handedness?

Apparently, the eye-side is determined by species. Some flounder, such as the summer flounder, have eyes on the left side of their head. Others, such as the winter flounder, have eyes on the right side. Although the names summer and winter make it sound like side preference may be a seasonal thing, the summer and winter flounder are two separate species.

From http://media.web.britannica.com/
eb-media/63/62563-004-98677738.jpg

Some scientist have examined the physiology of eye migration, and many different factors are proposed. Some have suggested that the retrorbital vesicles, located behind the eyes, may develop asymmetrically and push one eye to the other side. Others suggest that the development of bone on the side that will become the underside may contribute to one eye moving to the opposite side. Much like in amphibian metamorphosis, flounder metamorphosis has also been linked to thyroid hormones.

I always assumed that flounders were flat in order to be camouflaged to the ocean bottom and avoid predators. It would just seem natural, then, that one eye should not be digging in the dirt. But, as I learned while scouring the internet, having both eyes on one side of the head has other advantages. If you are familiar with visual perception, you may know that having two eyes allows us some system of depth perception. By having eyes joined on one side of the head, an adult flounder has better depth perception than other (normal-looking) fish and becomes a formidable predator.