One day you’re walking along a beach and you stumble across a docile Slowpoke fishing with its tail, a common method of hunting as it allows slowpoke to sit around lazily will its food comes to it. The sweet juices found in its tail is a tasty treat to other Pokémon (as well as humans according to the events of Generation II). Suddenly the Slowpoke flinches, you watch as it hauls its tail to find not a fish but a bivalve locked into its flesh – a Shellder. The Slowpoke gives you a blank look of surprise before its body disappears in a glow and before your eyes it evolves into Slowbro, who now stands upright and appears more aware than before. The Shellder too has also undergone physiological transformation, its color has changed to a dull grey and its shell resembles that of a mollusk more than a bivalve, outfitted with spikes for added protection.
You, the astute Pokébiologist, recall that many Pokémon group together in order to evolve – Magnemite form groups of three in order to become a Magneton, two Beldum fuse together to form a Metang, and two Metang combine to form a Metagross. But those instances only involved Pokémon of the same species, here we have one Pokémon interacting with a completely different Pokémon to trigger a dramatic transformation for both creatures. Moreover, each Pokémon retains its own consciousness as far as you can tell, they remain separate entities that are merely working in unison. The geneticist side of you suspects the work of epigenetics (see Eevee Epigenetics), but you are an ecologist at heart and recognize immediately the symbiotic relationship between the two organisms.
In nature, organisms will often interact with each other, as it is difficult to avoid contact with other living things even if you tried. Something as seemingly innocuous as stepping on a blade of grass is a interacting with another organism. We often classify these various interactions by how the organisms involved are affected. Predation, for example, involves the consumption of one organism by another organism, providing nourishment to one while ending the life of the other. However, not all interactions are as grim. In some circumstances, organisms will interact to the benefit of one or more parties, usually. This close and long-term relationship between two organisms is referred to as symbiosis, and can come in three forms, in which the organisms in questions either work harmoniously together (mutualism), harmlessly mooch off the other (commensalism), or completely exploit one to its detriment (parasitism).
In regards to Slowbro and Shellder, defining their relationship is a matter of determining which parties benefit, and which are harmed. This may seem a simple task but when dealing with the world of Pokémon things can become complicated quickly. In our own world, nature has a bad habit of not falling into the cookie-cutter labels we create in order to organize its chaos, and that is perhaps even more true for the Pokémon World.
An Honorable Mention: Amensalism
Amensalistic relationships are present throughout the natural world, and it is perhaps because of its prevalence that it is often left out of most textbook discussions on symbiosis. Amensalism can be defined as a relationship in which one party is unaffected while the other is harmed and somethings straight up obliterated. In truth, its classification is merely a technicality of the relatively broad definition used for symbiosis, which at one point was strictly limited to mutualistic relationships. Essentially, every organism is involved in an amensalistic relationship, and thereby kind of negates any purpose in highlighting it as its own relationship. Refer back to my previous example of you stepping on a blade of grass. That is an amensalistic relationship, the grass you crush is greatly inhibited, perhaps even killed, while you continue unaffected and unaware of the interaction you’ve just had. Obviously, Slowpoke and Shellder are both greatly affected, which immediately rules out amensalism, but I thought it warranted mentioning.
Commensalism: The Boring One
Commensalistic relationships are basically a step up from amensalism, one party benefits while the other remains relatively unaffected, neither helped nor harmed. These relationships are rather uneventful (hence the title), and are usually limited to interactions where one organism use another for transportation or housing. For example, mites will often occupy different organisms such as flies for transport, never feeding off of them or causing bodily harm. Some organisms will even use the body of another postmortem for housing, such as when hermits use the shells of deceased gastropods for homes.
Returning back to the Slowbro-Shellder Interaction, it’s fairly clear that Slowbro is indeed being harmed by Shellder biting down and remaining attached to its tail. Although, one could argue that Slowbro isn’t being harmed since, according to the Pokémon Silver Version PokéDex, “Naturally dull to begin with, it lost its ability to feel pain due to Shellder’s seeping poison.” However, just because an organism cannot feel the harm being inflicted upon it, does not mean it is not being harmed. Leeches release an anesthetic when they feed, allowing them to feed unnoticed by the host for hours until full. If I were to inject my sleeping roommate with an anesthetic, then stab him repeatedly in the gut as I tried to remove his kidney to sell on the black market, you would say I was harming even if he didn’t feel a thing. Not that I would ever do such a thing…
So case closed then. Slowpoke is very clearly being harmed. Shellder is a parasite. So we can completely rule out mutualism as well, right? Well, things are more complicated than that.
Parasitism: Violent Exploitation in the Natural World
Contrary to popular belief, parasites do not kill their host, or at least they do not intend to kill their host. You see, the parasites are locked in a special kind of symbiotic relationship, in which they derive sustenance from their host and thus will do everything in their power to keep them alive. If the host dies, the parasite will die most likely unless they can find a new body to mooch off of. That’s not to say that parasites won’t give the host a rough time, often the presence of a parasite can be debilitating to the host, perhaps killing them slowly rather than right then and there. This can be done through a number of methods – depriving the host of nutriments to feed itself, releasing waste products that can have deleterious effects to the host’s body, physically burrowing into and altering the structure of organs and tissues. In short, the fitness (survivability) of the host is sacrificed in order to advance the fitness of the parasite. The host could be on the brink of death but as long as the parasite can continue to survive, the relationship will continue.
Often when a parasite does kill its host it is either to fulfill a reproductive need, such as the lancet liver fluke which infects ants and compels them to hang to the ends of grass to be eaten by rabbits so to continue their life cycle, or it has accidently infected the wrong organism, one that has not evolved the immune defenses to keep it alive and functioning, as is the case with most fatal diseases that make the jump from animals to humans.
As we determined earlier, Slowbro is indeed harmed by the presence of Shellder, and Shellder does increase its fitness significantly attaching itself to Slowpoke, not only giving it free transportation, but also free food from feeding off of Slowbro’s scrapes, as well as the juices that run from its tail. Even the Bulbapedia page that I’ve pulled the PokéDex entries from states in the origins that “Its parasitic relationship to Slowpoke may be inspired by leeches.” So there you have it, confirmation from the top source of Pokémon information.
However, I have come to a different conclusion.
We must recognize that nature will not always fit so easily into the boxes we’ve constructed for it. Scientist often find trouble correctly labeling symbiotic relationships, perhaps at first seeing one as purely commensalistic only to later find that the other organism is being helped in some way. This gets even messier when trying to apply real-world logic to a videogame, a videogame that isn’t even consistent with its own rules and logic, as despite its various PokéDex entries, Slowpoke’s in-game evolution into Slowbro is completely independent of any interaction with Shellder.
Yes, Slowbro is harmed by Shellder, but I would argue that it is also helped, that Slowbro’s fitness increases when “infected” by Shellder.
If Ticks Gave Us Superpowers: Mutualism
The faint glimmer of hope that the natural world isn’t all doom and gloom is mutualistic symbiosis, an interaction between two organisms in which both parties benefit from the relationship. This reciprocal altruism often increases the overall fitness of both individuals, a great example can be found with the mutualistic relationship of sea anemones and hermit crabs – which are also an inspiration for Slowbro’s design. In the wild, certain species of hermit crabs attach sea anemones to their shells. In this relationship, hermit crab’s fitness increases by having an additional defense against predators – an array of stinging tentacles protruding from its back. Likewise, the sea anemone’s fitness also increases, as it is not only mobile (a great advantage for a normally sedentary species), but can also feed off the scraps if the hermit crab’s food (much like a certain grey-shelled Pokémon we know).
In the previous section we have already accepted that Shellder is harming Slowbro, that part is indisputable. But I would argue that Slowbro is helped more than it is harmed in its relationship with Shellder.
Firstly, Slowbro’s stats improve significantly upon evolution via Shellder, even more so when Mega-Evolved. Now, one could chalk thus up to simple game mechanics and claim that this increase in stats is not unique to Slowbro, and they would be right. However, Slowbro does undergo additional changes in its physiology and behavior. As Slowpoke, it walked on all fours, but now with Shellder attached it can stand upright. Additionally, it receive additional powers from Shellder’s attachment, as the Black and White PokéDex states, “Though usually dim witted, it seems to become inspired if the Shellder on its tail bites down.”
Lastly, I point to my final piece of evidence – Slowking. This often forgotten secondary evolution of this docile Pokémon also falls victim to Shellder’s parasitism. However, Slowpoke only evolves into Slowking when Shellder bites down on its head, giving the once seemingly senile Pokémon an ability few Pokémon outside of legendries have – speech. In fact, Slowking gains full human-levels of intelligence by simply donning a Shellder cap.
Slowking undertakes research every day in an effort to solve the mysteries of the world. However, this Pokémon apparently forgets everything it has learned if the Shellder on its head comes off.
Classified as the Royal Pokémon, Slowking also stands upright, and has intelligence comparable to award-winning scientist, even conducting scientific research. Think about it, a Pokémon is doing scientific research and publishing papers. A small reminder that moments ago this same Pokémon was sitting by a body of water, too lazy to hunt for prey and merely fishing with its tail hoping that it something will bite.
The secret seems to lie within Shellder’s venom, whose effects increase the mental abilities of Slowpoke, producing a moderately more adept yet still docile organism in Slowbro when just attached to the tail, and an intelligent being when latched directly above the brain as is the case with Slowking. Either way, the overall fitness of Slowpoke is increased significantly, ranging from just being able to obtain food more easily to literally becoming self-aware.
Thus, while Shellder may harm Slowbro initially, the perhaps unintentional effects of its venom on its host indeed brings a plethora of benefits to Slowbro and Slowking. It is neither strictly a mutualistic nor parasitic relationship, but an odd hybrid of the two. In our world, it would be like if ticks gave us superpowers when they feed on you, instead of Lyme disease.
The Slowpoke line is a fascinating line to study, and provides great insight on the various interactions between Pokémon species that the games don’t often shed much light into. But with a little over analysis and speculation, we can make some sense of this, at times often, senseless world.