A Bee-utiful Look Into Basic Bee Neuroanatomy

no one:

absolutely no one:                          

me: LeT's LeArN aBoUt bEe BrAiNs
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What up y'all, Ron here. I figured that I'll do something slightly different for this blog post and teach you guys a lil' something about bee neuroscience!



Because, well, why not? Besides, I figured that it would be interesting to look into (me being a neuro kid and all) so, hey, this could be a learning experience for all of us here!

The importance of antennae

Honey bee antennae are very sensitive organs that deal with a lot of information, including:
- olfaction (smell)
- somatosensation (touch)
- gustation (taste), and
- air motion (for flight speed)
Since these organs are very sensitive, bees have to frequently clean them using their front legs to keep them in tiptop shape (4).


Holy heck aren't they adoooooooooooooorable??

Olfaction

A bee's sense of smell is particularly important both on a colonial as well as on an individual level. As an example, bees release an odor called the "alarm pheromone" if they sense danger, letting other bees know of the danger and allowing them all to prepare accordingly. Bees can also use their sense of smell to locate sources of nectar and find their way back to their hives. In fact, if a bee shows up to the hive without having the correct odor, the guard bees at the front of the hive will even expel them! (4)


A bee preventing an invader from entering the hive (1967, colourized).

Somatosensation

Bees also have a well-developed sense of touch, extending from their antennae to all of the tiny tactile hairs throughout their body (3). Through their sense of touch, bees can gauge the physical dimensions of an object, such as a honeycomb (4). Bees can also use their sense of touch to communicate with other bees as is the case of their adorable waggle dancing, which is how bees share information about flower patches for potential nectar sources.

One of the first recordings of a bee communicating a nectar source to other bees (1564, colourized).

Vision

Bees have two kinds of eyes: their three small ocelli (singular ocellus) and their two big compound eyes. The ocelli are simple eyes with single lenses that help the bee navigate by judging light intensity, allowing them to stay properly oriented in flight (5, 6). Their compound eyes, meanwhile contain thousands of smaller eyes called ommatidia (singular ommatidium) that form thousands of images that are then integrated by their brain to form a cohesive picture of their surroundings (6). If you want to know more about bee vision specifically, this article goes into much greater detail.

The central nervous system of a honey bee

The central nervous system (CNS) of any organism is widely regarded as its most important organ system because it takes in information from the organism's environment and allows the organism to respond accordingly.

While the human CNS consists of the brain and the spinal cord, the CNS of a honey bee consists of the brain and various ganglia (singular ganglion; a cluster of neuronal cell bodies in the periphery) distributed throughout its body (2). The honey bee brain integrates the processing of its senses, whereas its ganglia mediate locomotion and other autonomic unconscious processes. As an example to see how these work together, a beheaded bee would be able to walk and move its legs around, but it would be unable to fly as it has no head to process balance and coordinate flight (2)!

The bee brain

Despite being no bigger than a sesame seed and only having about 1 million neurons (compared to the 100 billion neurons that we humans possess), the brain of a bee is highly structured and highly specialized. Sensory information from the antenna is received by the antennal lobe (AL) of the bee brain, while visual information is mediated by the medulla (ME), lobula (LO), and protocerebral lobes (PL), as shown below (7).

All of this sensory information is then sent to a highly dense and highly specialized pair of neuronal cell body clusters called the mushroom bodies (MB). The MBs act as an association area and take in various sensory information to interpret them for higher-order processing (1). In doing so, the MBs allow the honey bee to learn all about its environment, act upon the sensory stimuli immediately, and then use it for the future. In one study, bees have even been shown to remember a visual stimulus and see if it matches a new visual stimulus, indicating that bees have the capacity for visual memory and for more complex decision making (8).

A bee undergoing rigorous scientific experimentation (1945, colourized).

All in all, in case you haven't caught on yet, bees are rad as heCK. This blog post baaaaaaaaarely scratches the surface and I still have a lot to learn myself about bee anatomy (potential allusion to future posts by me, question mark?). If you need something else to satisfy your bee anatomy fix in the meantime, here's a rad video on how bees see the world around them! 

References

1. Barron AB, Gurney KN, Meah LFS, Vasilaki E, Marshall JAR. Decision-making and action selection in insects: inspiration from vertebrate-based theories. Frontiers in Behavioral Neuroscience 9, 2015.
2. Calvert C. Nervous system of honey bee [Online]. LinkedIn SlideShare: 2014.
3. Foden S. How Do Honey Bees Smell, Feel and Taste? [Online]. Animals: 2017.
4. Information Sheet 6 [Online]. Information Sheet 6, Honey Bee Senses. College of Agriculture and Life Sciences, University of Arizona.
5. Paulk AC, Dacks AM, Phillips-Portillo J, Fellous JM, Gronenburg W. Visual processing in the central bee brain. Journal of Neuroscience 29: 9987-9999, 2009.
6. Riddle S. How Bees See and Why It Matters [Online]. Bee Culture 2016.
7. Rybak J. The digital honey bee brain atlas. Honeybee Neurobiology and Behavior, 2011.
8. Zhang S, Bock F, Si A, Tautz J, Srinivasan MV. Visual working memory in decision-making by honey bees. Proceedings of the National Academy of Science 102: 5250-5255, 2005.

- Ron Miguel B.