The “Science” of Silence: How Crobat wings work

Back in generation 1, when we were young and excitable, we began our journey with enthusiasm. What Pokemon would we catch? Where are the Pokemon hiding? It didn’t matter who showed up in the grass, we loved them all! That is, until we took the fateful step into Mount Moon. Inundated by Zubat after Zubat, many of us learned to hate this bat that continuously confused us. But generation 2 was a kinder generation, and somewhat redeemed Zubat upon the introduction of its fully evolved form, Crobat.

Crobat is, obviously, based on a bat. However, it has four wings instead of two. According to the Pokedex “As a result of its pursuit of faster, yet more silent flight, a new set of wings grew on its hind legs” (C). This fast and silent flight is one of the major traits of Crobat, as it is mentioned in many of its Pokedex entries. Bat wings are really just modified hands. If you look at a bat wing stretched out, you can see the long bones that resemble finger bones. The skin over these bones is leathery and so thin it is translucent in the right light. The substantial width of these wings allows the bat to propel itself from the ground (or branch or cave) by pushing air downwards, generating enough force to push itself up. Once in the air, the useful shape and lightness of the wings also allows the bat to glide through the air. The speed we can attribute to its extra pair of long wings, but how does it fly so silently?

Crobat

One of the most notable animals with silent flight is the barn owl. Unlike most birds, you can rarely hear the swish of air that results from a barn owls wings. This is because the fine, primary feathers on the barn owls wings are separated to have a serrated edge, like a comb. This cuts the turbulence caused by their wings” into smaller units, which produce less sound. This is extremely useful to the barn owl, as it is able to sneak up on prey. It is easy to replicate this effect in real life. Wave a hand held paper fan up and down and listen to the noise. Then, slice the fan into segments and separate them slightly, like fingers, and wave it again. The sound caused by the fan will decrease as less turbulence is produced.

Barn owl in flight

However, Crobat doesn’t have feathers, and so must rely on a different mechanism. Insects with wings can only control the joints at the end of their wings, so all they can really do is flap. Birds have more joins, and can therefore use the finger like bones in their wings to increase their manoeuvrability. However, the finger bones in bat wings are far more advanced, and a bat therefore has a huge amount of control over the shape and movement of its wings. Not only do they wave their wings up and down, but they can also subtly change the shape of their wings during flight.

Furthermore, the skin on the wing of a bat is stretchy and can balloon slightly when it pushes down. This allows more air to be utilised under the bat’s wings so it does not have to flap as much as a bird or an insect, even if it isn’t gliding. This makes the bat an incredibly efficient flyer.

Bat wing anatomy

Crobat may utilize this technique also. It possible that it can fly silently through a combination of needing to flap less and opting to glide, and also by subtly changing wing shape to catch up drafts noiselessly because its wing bones are far more advanced than an ordinary bat. It also has four separate wings that can be used individually to catch different areas of wind, in order to glide silently for long periods of time. Furthermore, the four wings may help to break the turbulence into smaller units, in a similar manner to the comb shape of the barn owl.

Obviously, the silent flight of Crobat is likely to be an incredibly complex system, but this may provide a very simple basis.

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The “Science” of the birds and the Combees Part 2: All my sons

In the previous part of this series, we saw that it is pretty easy for a queen bee to decide whether to have male or female offspring. Vespiquen are definitely all female, but Combee has a strange skew in the likelihood of being a male or female. In fact, any Combee egg has an 87.5% chance of being a male. This is particularly strange, because bees have significantly more females in their colonies than males. What’s going on with all these male Combee?

combee

In the bee colony, some seriously strange things go on. Female worker bees grow stingers due to their lifestyle and chromosome number. The bee stinger is really a modified ovipositor, which is the organ responsible for laying eggs. Worker bees don’t bother laying eggs, so their stinger grows sharp and barbed. The Queen has a smoother stinger, and the males have no stinger at all, thanks to not having an ovipositor.

Main organs of a worker bee.
The male Drone, female Worker and Queen. The queen and worker bees both have stingers, but the worker does not have a functioning ovipositor

With Combee, they don’t really need to worry about having stingers or not because they can use moves that animals can’t, such as bug bite and bug buzz, to protect themselves and their colony. Also, male Combee can collect honey and contribute to the running of the hive, which real drones don’t do. Their ability to work is not at all inhibited by their chromosome count.

 

Something still doesn’t add up. When we want a baby Combee, we can put Vespiquen and a male pokemon into the daycare, and we will get a bunch of eggs. However, I don’t think they are actually breeding in the same way as other Pokemon breed. Every so often we will get a female Combee, because the Vespiquen bred with a partner, but most of the time the Vespiquen doesn’t breed, it just produces a haploid egg by itself, which hatches into a male. She may just be in a safe and happy environment when she is in the daycare and so she breeds happily, even though it is just by herself.

 

Is there even a reason she would want to have more males than females in her colony? As we know, the male Combee can actively contribute to the running of the hive. That means they actually have an important role and aren’t limited like Drones. However, because they are haploid and got all their genetic material from their mother, they have 100% of the same DNA as the mother and are very, very loyal to her. Due to a thing called Kin Selection, animals that have really high relatedness to each other are more likely to work together, so these males will work together very happily in order to protect their mother. However, a female Combee is only 50% related to her mother and (because of some crazy genetics) 75% related her sisters, and will therefore be more loyal to her sisters than her mother. Now, females require mating, are less related and loyal to their mother, can only forage and defend as well as a male, and there is always the possibility that they may one day try to usurp their mother or leave the colony if they evolve into a Vespiquen. So from this point of view it is much better for a mother Vespiquen to produce male offspring.

Bee relatedness

The Pokemon world doesn’t always match up with our world, but using the principles of science we can still look at it and come to conclusions about how it all works together. So next time you think a Pokemon is strange, investigate the reasons it might be that way, because you may come to an interesting conclusion.

 

More stuff to read

Gempe, T. & Beye, M. (2009) Sex determination in honeybees. Nature Education 2(2):1

Foster, K. R., et al. (2006). Kin selection is the key to altruism. Trends in Ecology & Evolution 21(2): 57-60.

The ‘Science’ of the birds and the Combees Part 1: Are you a boy or a girl?

combee
Vespiquen and Combee

Every so often in the Pokemon world, we come across a Pokemon that has a special evolution based on the biological sex of the animal. Some examples of this are Gallade, Salazzle and Vespiquen. The latter example, Vespiquen, will only evolve from a Combee if it is female. Vespiquen, unsurprisingly, is based on the queen bee of a bee hive and is said to look after all the Combee in her colony. The bottom of her body looks like the hexagonal walls of wax that hold eggs and larvae and she also secretes pheromones to control the larvae she raises.

Vespiquen.
Vespiquen

Obviously, Vespiquen are all female because they are based on the female queen bee, but the thing that makes this Pokemon really interesting is how the thing it is based on, female bees, came to be female. It is all based on chromosomes.

In humans, sex determination is due to a certain combination of chromosomes, which group together in pairs. Chromosomes are structures that hold highly compact DNA and genes. Different genes are on each chromosome, so the specific chromosomes can determine various features. Human sex chromosomes we have two variations; the X chromosome and the smaller Y chromosome. The egg produced by females in the ovary only has an unpaired chromosome and it is always an X. When that egg meets a sperm, the other sex chromosome pairs with the X in the egg. The sperm can either carry an X or a Y.  An XX combination will lead to a female, and an XY will lead to a male. We get one chromosome from each of our parents and that determines our biological sex. Having a pair of chromosomes like this is called diploidy (di refers to two, and ploid refers to chromosomes)

human chromosomes
Sex determination in humans is caused by combinations of X and/or Y chromosomes

That is all straight forward in humans and most animals, but bees like to buck the system. First of all, not all Bees are diploid; Some are haploid and only contain a set of single chromosomes, instead of a pair. What really makes this interesting is that it is not the type of chromosome that determines sex but whether the offspring are haploid or diploid, which all depends on the queen.

The bee colony is made up of the mother queen, the female workers, and a few male drones. The queen bee in a colony is responsible for giving birth and will have given birth to most of the colony. In humans, a baby can only be made with both a mother and a father, and queen bee will also produce eggs that have been fertilised by a male, and result in a diploid larva. The queen only needs to mate once, with 10 or so males, and she stores up the sperm from that event so she can use it for her entire life (1-5 years). She gets to decide which eggs get fertilised and when. These diploid larvae will ALWAYS be female.

But this is where it gets weird. The queen doesn’t actually need another male bee to reproduce. If she wants, she can lay a viable egg all by herself. Of course, like the example in humans above, this egg will only have “half” a chromosome pair and will therefore only have a single chromosome. In humans that would be unviable, but in bees, this will lead to a male.

Bee chromosomes
When a queen breeds with a drone, a female is born. When a queen lays an egg by herself, a male is born

So all that weirdness culminates in this; Female bees are produced from fertilised eggs and male bees are produced through unfertilised eggs. Females are diploid, and males are haploid. It is determined by the amount of chromosomes, not the type.

But bee breeding doesn’t stop there. Why, exactly, is it evolutionarily beneficial for a male bee to be haploid? When a male bee breeds with a queen he contributes 100% of his DNA to the offspring and the queen contributes 50% of her DNA. Sisters from this union will therefore share 50% maternal DNA and 100% paternal DNA between them, and leads to a very strange occurrence when all of the females produced from that breeding pair are 75% related, instead of 50% related like offspring from two diploid parents. This method of breeding is a way of keeping the bees genetically related and loyal to each other, as well as attempting to preserve good genes (of course, some are only half sisters with different fathers, but the principle above is sufficient that it doesn’t matter). Having only the single chromosomes prevents males from growing stingers, and they make awful workers, so they don’t bother with that. They are built for breeding, and that is about it.

Bee relatedness.png
Bee relatedness is denoted by a blue arrow. The queen is 100% related to her sons, the daughter is 100% related to her father, 50% to her mother and 75% related to her sister. Female Combee have a red triangle on the bottom head

It is quite possible that female Combee are the only Combee that can evolve because they have a whole lot more chromosomes. The male Combee are just held back by have a set of single chromosomes instead of a pair. In real bees, haploidy prevents stinger growth and workability, but in Combee, it prevents evolution. This method of sex determination may or may not also apply to Beedrill, but Metapod isn’t inhibited from evolving into a Beedrill due to its chromosome count, but it seems like Vespiquen is all about the chromosomes!

First image was made by Haychel and is found at https://haychel.deviantart.com/art/Vespiquen-Speedpaint-397814977

More stuff to read

Gempe, T. & Beye, M. (2009) Sex determination in honeybees. Nature Education 2(2):1

Foster, K. R., et al. (2006). Kin selection is the key to altruism. Trends in Ecology & Evolution 21(2): 57-60.

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