Dr. Tracy Farone
The Hexagon, Under the Microscope
Dr. Tracy Farone
Each Fall for about 10 years now, I have had the joy of teaching a course called “Histology.” Histology is the study of cells, often with the aid of a variety of microscopes. It is not a sexy course title, but the course content is relaxed and involves looking at a lot of colorful pictures. My students spend hours peering through the lens of a microscope trying to visually decipher the blobs before them. By the end of the course, after enough staring, most students achieve the skill of identifying “the blobs” as some specific cell or tissue. Since the late 16th century, the study of histology has given humans the opportunity to give things a “closer look,” and the technology is ever increasing our ability to “see” beyond the cellular level.
Histological identification certainly has many practical applications in biology, health care, disease diagnosis and in beekeeping. Closely examining our honey bees’ body cells has led to the understanding of their functional anatomy, physiology, pathological tendencies and disease diagnosis. What I find incredibly fascinating is the link between the shape of our honey bees’ comb cells and what is also found microscopically in many of our body’s tissues. The hexagon. (See Photo 1)
I am sure you have read articles about this shape, which is so often associated with the beautiful honey comb pattern of our bees, and how hexagons are the most effective and efficient geometric shape. These six sided polygons can tessellate any plane to completely fill the area with no gaps. From art to architecture, in snowflakes, soap bubbles and soccer balls, natural design or man-made, hexagons are everywhere, appreciated as a symbol of strength, stability and security. But have you heard about the hexagon from a histologist’s perspective? Well, allow me to give you a different take. Here is today’s lesson:
Common types of microscopes and honey bee applications
1.Dissection scopes: Dissection scopes are commonly used to view smaller, 3-D things (like bees) with up to a 100x magnification. These scopes are helpful in studying plant and insect morphology, and for taking “zoomed-in” photographs. (See Photo 2)
2.Optical light microscopes: These scopes are probably what you imagine when you hear the word “microscope.” Using visible light and a series of lenses, these scopes typically can magnify objects up to 2000x. Examined specimens are typically prepared onto slides for viewing. These microscopes are invaluable in diagnosing a variety of abnormal cellular formations and infections in man or bee, including parasitic, bacterial and fungal diseases.
3.Electron microscopes (EM): Electron microscopes actually use a beam of electrons (not light) to create images magnified millions of times. They are typically found in research labs and universities. There are two major types:
a.Scanning Electron Microscope or SEM: Scanning electron microscopes create a sharp almost 3-D like image of the surface of a specimen. Magnification ability of a SEM can reach one-half a million times. We have a SEM in our lab that my students use to capture cool images of honey bees and their parasites. (See Photo 3)
b.Transmission Electron Microscope or TEM: Transmission electron scopes capture a flattened slice of tissue magnified up to fifty million times. TEMs can be useful in diagnosing and studying pathogens.
4.Fluorescent microscopes, FS: Fluorescent scopes utilize fluorescent dyes added to a specimen to tag certain tissue components or pathogens. When exposed to UV light, these fluorescent dyes absorb lower wavelengths of light and then emit a higher wavelength or seem to “glow.” If the examined sample glows appropriately, we know that we have found what we are looking for… amazingly, there are now small, portable FS that work with a smart phone to detect Nosema in honey bee samples in the field. Yep, there’s an app for that!
Histological Hexagon Examples
Many of our body’s cells are designed in a hexagonal mosaic. Chemists could even argue that at a molecular level, all carbon-based life forms contain a base of hexagonal carbon rings, but I am not a chemist, so let us just look at what we can see (through a microscope).
The urinary bladder, for example, has a unique and specialized ability to expand and contract over short periods of time. This can come in handy when you have had that extra cup of coffee! This peculiar capability also comes with a unique design. As with most things in nature, form and function are always complimentary. The bladder has a specialized type of tissue that lines its interior called transitional epithelium. It is called transitional because these cells of the bladder are shapeshifters. They range from almost flat to taking on the appearance of an overstuffed marshmallow. When the bladder is full, the cells spread out and take on the shape of, you guessed it, the hexagon (See Photo 4). Even a vessel that is given the lowly task of holding urine, has a beautiful design from the inside out.
The liver is the second largest organ in most mammals and performs thousands of functions necessary for the preservation of the body. (Even honey bees have an organ that mimics the important work of the liver, in their fat bodies). The liver is arranged in rows of cells, stacked in columns forming a sieve in which blood can slowly flow through the organ, so that each drop can be processed by the liver cells, or hepatocytes. What shape to best accomplish such a feat? Yep, again – the hexagon. Each hepatocyte itself is a hexagon, which then combines in groups to form larger units called lobules, also hexagonal, collectively, in shape. Again, the hexagon is the best way to get the most things done in the best use of space. (See Photo 5)
Other six sided cell examples in histology include the inside surface in much of the small intestine, which takes on the appearance of hexagons with a fuzzy border of projectiles, called microvilli. These shaggy microvilli help to increase surface area to facilitate the absorption of our latest meal (See Photo 6). Another example are insects’ eyes, including our honey bees’ eyes. These compound eyes are made of thousands of individual eyes arranged in a hexagonal mosaic pattern (See Photo 7). Even the very fibers of our own eyes’ lenses are composed of long layers of hexagonal cells. (See Photo 8). Hmmm, ironically, I suppose we are looking at hexagons through a bunch of hexagons.
Well, that is enough for today, class. If you look around, you may be able to find a dissection or optical scope on the cheap to play around with and get a closer look at your bees. Since I have become a beekeeper, I am yet to find a subject that does not somehow relate back to bees or the study of them.
References:
FS in Nosema detection: https://pubmed.ncbi.nlm.nih.gov/30719512/ accessed March 28th, 2022.
