Tag Archives: asexual reproduction

Azurill – The Hermaphrodite Pokémon

At first glance, Azurill may seem like another forgettable baby Pokémon. This poor water mouse is easily overshadowed by its evolved forms – Marill for igniting the myth that became Pikablu, and Azumarill for its use in competitive play. Indeed, the only memorable characteristic about this Pokémon is its frowning sprite, probably begging to be put out of its misery for being relegated to Gen II dex filler. However, do not let that incredibly heart-wrenching face fool you, because Azuril does have one thing that sets it apart from the other 721 Pokémon currently in existence. Azurill, upon evolution, can change its gender. Azurill is a hermaphrodite.

Until Generation VI when this was fixed, Azurill had a gender ratio of 75% female and 25% male, while both Marill and Azumarill had an even 50:50 split between male and male. Thus, upon evolution into Marill, female Azurills actually had a one in three chance of swapping gender and evolving into a male Marill. Imagine the surprise of the unsuspecting player to find out the female Azurill they had raised and probably given a gender-appropriate name was now a male.

In biology, this phenomenon is referred to as hermaphroditism, and an organism that has both the reproductive organs of both the male and female sexes is a hermaphrodite. This trait is most common in invertebrates such as gastropods, earthworms, and jellyfish, as well as flowering plants.

Hermaphrodites fall into two categories – simultaneous and sequential. Simultaneous hermaphrodites continuously bear male and female reproductive organs throughout their lives. Garden snails are a well-known example of simultaneous hermaphroditism. The snails still mate and produce offspring that are genetically unique, however self-fertilization is not uncommon for simultaneous hermaphrodites, as plants often self-fertilize in the absence of pollinators. Some organisms such as earthworms have defenses in place to prevent self-pollination.

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Snails exchanging sexual material. The longer you stare at it the less disturbing it becomes.

 

The world of simultaneous hermaphroditism is a fascinating if not strange place, as evident by the unsettling number of photos of invertebrates in various stages of copulation I’ve been forced to shuffle through in order to write this blog post. But personally, I find the sequential hermaphrodites more interesting, in that they are born as one sex but later switch later in life.

A creature such as Azurill, would be classified as a protogynous hermaphrodite, an organism that was born female but changes to a male. Protogyny is common among fish, some of the few vertebrates that exhibit hermaphroditism. Female wrasses, for example, may change into males upon a shortage of the opposite sex, developing testes in place of ovaries. However, this change is irreversible, and only females can make the change, although, under laboratory conditions, males have been known to also swap genders.

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Wrasses often organize into “harems” in which mating typically takes place.

 

Azuril appears to fall into the same boat of the wrasse, with females being the only ones able to change gender, as well as it being an irreversible process. While the in-game cause of this phenomenon may lie in perhaps an oversight on the game designer’s part, from a pure evolutionary viewpoint, Azuril’s hermaphroditism could provide a similar benefit as the wrasse, balancing out the gender ratios when they fall out of whack. But that’s just me applying real world logic to a videogame, again.

Exeggutor: A True Freak of Nature

The Pokémon World and our own world are similar in that the natural processes that govern life produce some strange creatures. Perhaps one of the most odd (and unsettling) is Exeggutor, the dual Grass Psychic-type that wanders around with its three grinning coconut heads resembling some unholy hybrid between a palm tree and several stoners. Yet our anthropomorphic palm tree friend is quite the interesting specimen when put under the lens of real-world biology.

 

A Free-Thinker of Many Heads

The most obvious abnormality of Exeggutor at first glance are its three heads, each with their own distinct and unsettling facial expression. According to the PokéDex entry in Pokémon Gold Version, “Its three heads think independently. However, they are friendly and never appear to squabble.”

This leads to quite the impressive nervous system, especially for a plant. But quips about plants not having any neurons aside, it is not unfounded in nature for animals to have multiple “brains” per say. For instance, octopi have nine brains, the main brain being located in its head with eight auxiliary brains in each of its eight tentacles. When an octopus desires to operate one of its arms, the main brain sends a single message to the nerves located in its arms, and then the arm “brain” proceeds to carry out the order all on its own. Even when severed, an octopus arm will still respond and react to stimuli the same way it would if it were attached to the complete organism and main brain1.

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Due to the complexity of their nervous systems, many people have a moral objection to the consumption of cephalopods.

 

However, unlike Exeggutor, the auxiliary brains of an octopus do not have their own consciousness. A severed octopi arm does not a new octopus make.

A particularly fascinating condition is that of polycephaly. A polycephalic organism is born with two or more heads, either as a supernumerary body part or as completely separate beings sharing a body, as the case is with Exeggutor. Usually the result of faulty twinning, polycephaly never results in more than three heads (tricephalic), with two being the norm (dicephalic). Unfortunately, in both humans and animals, dicephalic organisms rarely survive, as the two heads will often fight with each other for control over the body, often becoming disoriented, which makes for difficulty in fleeing predators. Polycephalic snakes have been known to even attack and consume their other head. Thankfully, Exeggutor appears to be a peaceful organism and its heads are very cooperative, as “they never appear to squabble”.

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Those that handler polycephalic organisms often report having to place a barrier between heads in order to prevent one from eating the other during a feeding.

As deleterious as this condition may be in our world, the trait seems to be of advantage in the Pokémon World. In the Crystal Version PokéDex, “Living in a good environment makes it grow lots of heads.” Apparently the selection pressures of the Exeggutor’s ecosystem make it so that having multiple heads is an advantage, running completely counter to our world which usually follows a general rule of the more appendages an organism has to manage the more energy required to maintain them all. In the game of evolution it’s all about the costs and rewards, having an extra head or two is just too taxing and hardly reaps any benefits.

While selection of polycephalic individuals may seem paradoxical at first, there is good reason for the Coconut Pokémon to expend energy growing its extra heads, and the answer lies with the endgame of survival, arguably the purpose of life – reproduction.

 

Dropping Heads: Clonal Fragmentation

Counter to what is portrayed in the videogames, Exeggutor does not need another Exeggutor (or any Pokémon of its egg group) to reproduce. In its natural environment, when not forcibly bred by overanxious trainers eager to create an IV master race, Exeggutor can reproduce asexually simply by parting with one of its heads.

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“If a head grows too big, it falls off and becomes an Exeggcute.” – Diamond/Pearl/Platinum PokeDex

More specifically, Exeggutor appears to reproduce through clonal fragmentation, a form of asexual reproduction most common in flatworms, sponges, annelids, sea stars, as well as mold, lichens, types of cyanobacteria, and many plants.

The process of fragmentation involves a piece of the organism splitting off to regenerate into a complete organism that is also able to reproduce. For example, tapeworms live in the digestive tracks of mammals, usually dogs and sometimes humans (either intentionally or, depending on the type of person, on purpose). As you can imagine finding a mate in the middle of a dog’s small intestine can prove troublesome, but all a tapeworm has to do is release an end segment of its own body down the track, and with some time Rover will have an infestation of new tapeworms, grown from the end bits of the original pioneer that first ventured into his bowels.

D. caninum ex dog.  Given by Peter Schantz

If you find one of these segments in your pet’s feces (or your own), seek medical attention.

As is common in binary fission, this often results in the regenerated fragment being genetically identical to that parent, making all Exeggutors clones of each other, the regenerated offspring of past Exeggutors whose heads grew too large to support. However, this process, as is the case with most forms of asexual reproduction, does have one major drawback, in that since all organisms are effectively clones of each other, there is no variation, and as any good biologist (or PokéBiologist) knows, genetic variation is the driving force of natural selection and therefore evolution. But this shouldn’t be a problem for Exeggutor, they seem to be plentiful enough, and pending an Exeggutor superbug, they will continue to endure for many generations to come.

Of course, there is the unique caveat that with Exeggutor, a single fallen head does not a new Exeggutor make, rather the individual Exeggcute have to swarm together, usually in groups of six in order to eventually “evolve” into an Exeggcute. Communicating telepathically, these eggs seem to form somewhat of a superorganism…but that is a topic for another day.

 

Cited Sources

http://news.nationalgeographic.com/news/2001/09/0907_octoarm.html

Kangaskhan – Parental Bond and Parthenogenesis

Ever since its introduction in the Second Generation, the concept of Pokémon breeding, while greatly appreciated, has spawned a plethora of questions, including, but by no means limited to – how can completely different species successfully copulate? How can they produce fertile offspring that are functional and not riddled with genetic malfunctions? Why is a tiny little cat able to have sex with literally the largest Pokémon known to us thus far? Perhaps one of the largest contributors to this pool of questions is Kangaskhan, a species that is 100% female and is born already equipped with a baby in pouch.

There is much to be said about the Parental Pokémon, aptly named since it literally enters the world a mother. It comes as no surprise that its design is inspired by the kangaroo, yet there is so much more to learn from her. Indeed, Kangaskhan is more than a magical marsupial, she is a shining example of the remarkable process that we in our world know as parthenogenesis.

 

A World Without Men

Time to have a talk. The Talk to be precise.

Excuse me if my heteronormative bias shows here but typically speaking, a man will encounter a woman and either through coercion or brute force insert his penis into her vagina and deposit his half of the reproductive materials via ejaculation. His materials, commonly known as sperm, enter the vagina, with a few lucky individuals making it past the cervix to – if this woman he has taken is ovulating – join with a nice plump egg waiting to be fertilized. The first sperm to penetrate its outer membrane wins the prize of fusing with the ovum to form a zygote and nine months later a baby is born.

We call this process sexual reproduction and it requires the existence of two sexes at minimum (though there can be more in some cases) since its main selling point is the promotion of diversity. Like a college admissions department, diversity is the name of the game when it comes to genes. More variation means more unique individuals with traits that may or may not prove advantageous in life. However, sexual reproduction is not the only way to make a baby.

If diversity is not really your interest and you’re just looking to pass on your legacy without the energy and drama that comes with sex, asexual reproduction may just be what you’re looking for.

In asexual reproduction, no new genetic material is added. The next generation is genetically identical to that before it with no variations other than the random mutations that still occur during DNA replication. Naturally, this leads to severe lack of diversity with very few, if any, differences between individuals, but has the benefit of not needing to expend energy in courtship and actual mating. Additionally, asexual reproduction only requires one sex.

There are many forms of asexual reproduction – budding, binary fission, clonal fragmentation. But perhaps the most interesting form is parthenogenesis, essentially virgin birth. Offspring of parthenogenic organism develop from unfertilized eggs. Most organism that use parthenogenesis do have two sexes, as well as the ability to reproduce sexually, and often fall back to it when conditions become adverse and the diversity is needed1. However, there are some species, such as Kangaskhan, that have abandoned the entire male line in favor of an all-female feminist utopia.

Take for example Aspidoscelis uniparens, the whiptail lizard, a species that contains no genetic males and reproduces completely through parthenogenesis. Oddly enough however, the females of this species do engage in mating rituals similar to that if they were reproducing sexually which enhances ovulation. Furthermore, despite being asexual, whiptails have managed to find a way to preserve some degree of genetic diversity through combining sister chromosomes instead of homologous chromosomes2.

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A conservative’s worst nightmare — a society of promiscuous female lesbians with no male supervision.

 

It appears that Kangaskhan has taken a similar evolutionary path to the whiptail lizard. Being a male-free species can have its benefits especially for a creature as devoted to its young as Kangaskhan. The PokéDex entry in Emerald appropriately states, “If you come across a young Kangaskhan playing by itself, never try to catch it. The baby’s parent is sure to be in the area, and it will become violently enraged.” With sexual reproduction comes competition between not only the sexes but between competing males, each vying for a womb to continue his genetic legacy, and children are often the first casualties in this war, as it is not rare for a male to kill the offspring of another male so to ensure his are the only ones that end up surviving. With Kangaskhan’s identity wrapped up in protecting its baby, a sexual society would prove troublesome, male Kangaskhan mutilating babies while forcing fertile females into copulation. A better situation could be created without the presence of males, one in which the young are protected and mothers rested easily without the threat of a male high on testosterone killing her child.

 

Parental Bond: More than an Ability

Perhaps more than any other class of animals, mammals have mastered the art of motherhood. Few other organisms take on the burden of reproduction to the extent that mammals do. From the moment of conception, the mammalian mother is dealt with the burden of having to carry and support what essentially boils down to a temporary parasite that drains off its energy over whatever period of gestation it takes. Then after the offspring has been born they are still tasked with the job of providing additional nourishment through a unique little gland named mammary (yes, that’s where mammal comes from), in doing so providing them with invaluable proteins, antibodies, and other goodies that’ll help them later in life.

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In humans, oxytocin is released in females during breastfeeding, further forging the bond between mother and child.

But for marsupials in particular, motherhood comes with some additional stakes. A joey (baby kangaroo) is born early in its development, with a gestation of only 30-36 days. The pink gooey bundle of joy resembles its distant cousin the gummy bear more than a kangaroo at this stage in its life, being no larger than a lima bean. Being basically a living fetus, the joey is especially vulnerable in these first months. However, it quickly climbs to the pouch with its barely formed forelimbs and latches on to its mother’s teat where it will reside for the next nine months, feeding on its mother’s milk from the safety of the pouch.

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You will never eat a gummy bear ever again.

 

 

One can imagine that it can get crowded quickly in a pouch. Thankfully, kangaroos have evolved a unique adaptation called diapause, in which a mother essentially freezes the development of an embryo while her pouch is occupied. Once the joey is old enough to leave the pouch for good, the embryo is allowed to continue its growth, thus allowing the kangaroo mother to allot all of her attention to the primary offspring on hand.

This being considered, I find it interesting that in Kangaskhan’s Mega Evolution, the vigilant mother finally lets her current joey from the safety of her pouch to fight side by side with her, herself unchanged by the actual Mega Evolution but her young larger and more plated, starting to resemble its adult form. Perhaps this particular event is more than just temporary battle effect, but the release of Kangaskhan’s current joey and the unpausing of diapause, in which the joey that resides in her pouch post-Mega Evolution is not the same joey that was in battle but the newly developed embryo grown into a joey after months of diapause.

 

 

Cited Sources

COLIN BLAKEMORE and SHELIA JENNETT. “parthenogenesis.The Oxford Companion to the Body. 2001. Encyclopedia.com. 15 Mar. 2016 <http://www.encyclopedia.com>

Lutes, A. A., Neaves, W.B., Baumann, D. P., Wiegraebe, W., Baumann, P. (2010). Sister chromosome pairing maintains heteroozygosity in parthenogenetic lizards. nature.com.