Rodrigo B. Salvador¹, Rafael M. Rosa², Fernanda S. Silva³ & Daniel C. Cavallari²
¹ Museum of New Zealand Te Papa Tongarewa, Wellington, New Zealand. Email: salvador.rodrigo.b (at) gmail (dot) com
² Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Ribeirão Preto, SP, Brazil. Emails: rafaelmassonrosa (at) usp (dot) br; dccavallari (at) gmail (dot) com
³ Museu de Zoologia da Universidade de São Paulo, São Paulo, SP, Brazil. Email: fernanda06 (at) usp (dot) br
ARK: Survival Evolved is a survival game, as one could expect by its title. It was developed by Studio Wildcard, in collaboration with three other studios, and was launched in its finished form in August 2017. Back then, the game was available on Xbox One, PlayStation 4, and the usual computer operating systems. ARK was later released for Android, iOS, and the Nintendo Switch.
The game was received by lukewarm reviews at best: its Metascore is 70 for PCs, and 69 for both PlayStation 4 and XboxOne (Metacritic, 2020). However, through the course of three years and four expansions, the game managed to secure a loyal set of fans and achieve a state of “sustainable revenue” (Batchelor, 2019). As of June 2020, the game had a total of 35 million installs, of which half is estimated to come from mobile platforms (Desatoff, 2020).
ARK can be played from both first- and third-person perspectives, where the players explore an open-world environment. The game is action-oriented, with plenty of harvesting and crafting activities. The players’ goal is to survive and prosper in the game world, called ‘Ark’, while facing natural hazards and dangerous animals, the most dangerous of which are likely the other players. Most creatures found in the game were based on real animals, typically extinct ones, like non-avian dinosaurs (Fig. 1). As biologists, we are, of course, not interested in those mainstream gargantuan beasts. Rather, we are drawn to another giant of more modest proportions: the giant snail.
ARK’S GIANT SNAILS
Let us start by taking a look at ARK’s giant snail, called ‘Achatina’. In fact, the “species” received a mock Latin scientific name in the game: Achatina limusegnis. Typically, a scientific name is accompanied by the name of the scientist(s) who first described it, like in Corvus corax Linnaeus, 1758, the common raven, who received its scientific name from Carl Linnaeus in 1758. ARK doesn’t pay homage to former scientists and omits the name of the person who described Achatina limusegnis.
Helena Walker, a character in ARK who’s supposedly an Australian biologist, left some notes on Ark’s various creatures. Helena’s dossier about Achatina can be seen in Figure 2.
Now let’s break that down. First: “very slow, very non-threatening land mollusk” sounds about right, although if Helena was indeed Australian as suggested she would have spelled it ‘mollusc’ (the ‘k’ is an American idiosyncrasy, but we prefer it that way). If it is attacked, it retracts into its shell, an obvious and typical behavior of snails.
Second: “meat and chitin”. Indeed, several real-world cultures have land snails in their cuisine. But chitin? Well, it’s possible, but not easy. Snails do have some chitin in their shell, but that’s quite a small amount, especially when compared to arthropods, whose exoskeleton is largely made of the thing. The primary component of snail shells is calcium carbonate (CaCO3). Even so, chitin can be extracted from it with some effort and the right equipment and chemicals (Adeosun et al., 2017; Oyekunle & Omoleye, 2019). Researchers have even extracted chitin from real-world Achatina (Gbenebor et al., 2017). Wait a second. Real-world Achatina? Don’t worry, we’ll get to that later on.
Next, there’s the whole “Achatina does not defecate normally” thing. ARK has a weird fixation with who defecates what and we’ll just skip this bit. Snails do poop normally, though. Anyway, Helena says that Achatina “secretes a thick, sticky substance” that dries quickly. That is, of course, slime or mucus. All land snails and slugs produce mucus for locomotion: they actually “glide” on top of it (Fig. 3). The mucus is a mix of chemical substances and can also serve as a defense against predators, microorganisms, and even as a shield against desiccation when the snail is aestivating (Barker, 2001; Cilia & Fratini, 2018).
Helena also informs the reader of the in-game use of Achatina’s secretions as crafting material (‘Organic Polymer’ and ‘Achatina Paste’, a substitute to ‘Cementing Paste’). Unfortunately, real-world snail mucus cannot be used that way yet, although researchers are trying to get there (Cho et al., 2019). In any event, snail mucus also has other applications. Due to its antimicrobial components, it can be used for cosmetics and skin-care, as well as to treat skin lesions and burns, (Brieva et al., 2008; Tsoutsos et al., 2008). It is even being considered a substitute for surgical glue (Li et al., 2017).
Chitin (and its derivative chitosan) also has several applications in the industry: food, pharmaceuticals, cosmetics, agriculture, textiles, and paper (Hamed et al., 2016). Researchers are also looking at the possibility of using it as a biodegradable substitute for plastic (Fernandez & Ingber, 2014) and also as building material for an eventual colony on Mars (Shiwei et al., 2020).
In ARK, Achatina can be domesticated so the players can “farm” the resources it produces. However, they are not breedable in the game, which is weird given their real-world counterpart (see below). ARK’s Achatina can also be a pet and, more importantly, can wear hats!
THE REAL ACHATINA
As mentioned above, Ark’s giant snails have the “scientific name” Achatina limusegnis. As such, it is not a huge leap to conclude that they were based in the real-world Achatina.
Achatina is a genus of pulmonate snails. This means that these snails breathe through a lung, instead of the usual gills found in most other molluscs. Lungs have evolved more than once among gastropods, usually in terrestrial taxa, rendering the traditional “pulmonate” classification obsolete (albeit sometimes useful) in current taxonomy. However, most lung-bearing snails, including Achatina and other iconic species such as the garden snail, are indeed related and gathered in a large group called Stylommatophora.
The Stylommatophora are the most diverse group of land snails, with a whopping 20,000 species total worldwide (Rosenberg, 2014). A distinguishing feature of stylommatophoran snails is having their eyes located on the tip of stalks, in contrast to the position near the base of the tentacles seen on most other gastropods. The eyestalks are also known as ommatophores and are responsible for giving the Stylommatophora their name.
Achatina and its closest relatives are grouped in the family Achatinidae (Fig. 4). This is a very diverse family, including around 1,000 species of many shapes and sizes (MolluscaBase, 2020). The Achatinidae range from the tiny awl snails, some of which are just a few millimeters long, to the gargantuan Achatina snails themselves, which include the largest of all land snails with shells growing over 20 cm in length.
There are approximately 40 species of Achatina, all of which are native to sub-Saharan Africa (Bequaert, 1950; MolluscaBase, 2020). However, some species, such as the infamous Achatina fulica (Bodwich, 1822), are highly invasive and are now found in tropical and subtropical areas worldwide. Achatina fulica (Figs. 4E, 5) is known by the common name ‘giant African land snail’; however, this species is so widespread and well-known that most people are equally comfortable with the scientific name.
Most of the diet of A. fulica is composed of vegetable matter of all kinds, including decaying vegetation, fruits, and leaves. In urban areas, it has been observed to eat even paper and cardboard! These snails can also eat meat, often sourced from animal carcasses (including other snails). In more than one instance, A. fulica has been reported to attack and consume living leatherleaf slugs (family Veronicellidae), which means they can hunt for meat as well (Meyer et al., 2008).
The invasive nature of A. fulica (and, to a lesser extent, other Achatina snails) is largely a result of human introductions. This species is native to East Africa and has been introduced to all other continents (except for Antarctica) both intentionally, as a food item or a novelty pet, and accidentally, as the snails can attach themselves to vehicles and survive long travels (CABI, 2020). The results are often disastrous to local ecosystems and crops, as A. fulica is capable of consuming hundreds of species of plants. Curiously, grasses, such as sugarcane and maize, suffer little damage from A. fulica (Raut & Barker, 2002; CABI, 2020). In addition to this, A. fulica adapts quite well to new environments and breeds intensely: a single individual usually lays 100 to 200 eggs at a time, but there are reports of a batch of circa 1,000 eggs (Mead, 1961; Pawson & Chase, 1984). The combination of these characteristics and the ensuing environmental damage led the IUCN to classify Achatina fulica as one of the world’s top 100 invasive alien species (ISSG, 2003; CABI, 2020).
Beyond the environmental impacts, A. fulica is known to carry several parasites. One of them is the nematode Angiostrongylus cantonensis (Chen, 1935), which can infect humans and cause severe cases of meningitis. The parasite is usually transmitted by eating the snail, but simply touching it can be enough. Since A. fulica is commonly found in urban areas, its invasions prompt a serious public health concern.
Achatina fulica thus seems to be a poor choice for a pet, but some people like to keep them, arguing they can be quite expressive and fun to interact with. They can live for five to seven years and can grow quite large in captivity: their shells can reach around 20 cm. Given the damage, they can cause to the environment, in many countries it is illegal to keep them as pets. Usual pets (cats and dogs), however, are extremely bad for the environment and are directly responsible for the extinction of dozens of species and still threaten hundreds of others (Medina et al., 2011; Gomper, 2013; Doherty et al., 2016, 2017).
COMPARING THE SNAILS
Clearly, ARK’s Achatina was based on Achatina fulica. Besides its name, the Wikipedia page of A. fulica is the very first result when you google “giant snail”. ARK’s Achatina is large for a snail, though, about the size of a reasonable dog, which is most unfortunately not feasible for real land snails. But other than that, how well does the virtual Achatina compare to its real-world counterpart?
Let’s start by taking a look at its external morphology. The shell of A. fulica is conical and rather elongated (Fig. 5). While the shell of ARK’s snail might look superficially similar, it is not so. It shows a flaw that is a typical mistake of artists when drawing snails: the shell is not spiral (see also Salvador & Cavallari, 2019). Snail shells grow in a spiral manner, with each successive new whorl growing on top of the previous one. While it might be difficult to visualize this just by looking at the photograph of a shell, you can easily see it if you have a shell on hand or by looking at an X-ray image (Fig. 6). ARK’s shell (Fig. 2) is like a hollow hood that just sits atop the snail’s soft parts like a hat.
The soft parts of ARK’s snail (except the colors, see below) are spot on (Fig. 2) and were likely drawn based on an actual photograph of Achatina (Fig. 4E). It has a pair of eye-bearing stalks (the ommatophores) and a pair of tactile and chemically sensitive tentacles. The skin on the dorsal surface of the snail (on its back, so to speak) is very rugose. But the sole of the snail’s foot also seems to be rugose (Fig. 2), which is mistaken. The “sole” of a snail’s foot is smooth, which is necessary for adhesion while crawling, especially on vertical surfaces or while hanging upside down.
The internal anatomy of ARK’s Achatina (Fig. 7) is also spot on, showing all the organs in the right places. But that is expected, given it was copied from schematics available on Wikimedia Commons (Fig. 7).
BIODIVERSITY ON THE ARK
One interesting aspect of ARK’s Achatina is that it has five different colors depending on the region of the game (Fig. 8). We shall call these ‘color morphs’, to use a more biological term.
Typically, when we see two similar snails with different colors they belong to two different species (Fig. 9). However, in ARK, all the different color morphs belong to a single species, Achatina limusegnis. But is it possible for a single species to have individuals with such varying colors? It turns out it is.
Take the grove snail Cepaea nemoralis (Linnaeus, 1758) from western and central Europe, for instance. It has a wide variety of color morphs: from whitish to yellow, orange, red, and brown, being either of a single color or presenting one or more dark stripes on the shell (Fig. 10). All these morphs belong to a single, though highly variable, species. Why there are so many different morphs has been hotly debated by scientists since at least the 1950s. Present hypotheses include (1) lighter colors being related to environments with higher temperatures, and (2) the presence of stripes being related to visual protection against predatory birds (Silvertown et al., 2011; Surmacki et al., 2013). Other famous examples of color morphs in land snails include the Cuban painted snail Polymita picta (Born, 1778) and the living jewel snail Liguus fasciatus (O.F. Müller, 1774) from Florida and Cuba.
The soft parts of the snails can also vary a bit in coloration, which is due to different amounts of pigments on the skin, just like in our species. There are even completely white snails like the ones in ARK (Fig. 8), which can be a natural coloration for some species or be “albino” individuals in some cases, like in A. fulica.
Now the red color seen in one variety of Achatina in ARK (Fig. 8A) is very unusual among land snails. The most famous example is the Malaysian fire snail Platymma tweediei Tomlin, 1938 (Fig. 11), which is a species with very restricted geographic distribution and highly endangered due to deforestation and other human activities. Its heavy metal looks in particular have made it a target for the pet trade, putting the species in even more danger (Foon, 2014).
ARK’s giant snail has a good bit of reality and a healthy dose of fiction. That is fine, as video games need to have some artistic liberties and not be too strongly anchored in reality. We cannot forgive the wrongly-designed shell, though, because that would be a simple matter to solve and would greatly improve verisimilitude. In any event, it is always good to see underrepresented animal groups in games, as they can help to raise awareness about their real counterparts among players and maybe – just maybe – help create a more environmentally-friendly mindset (Salvador, 2017).
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Many thanks to Junn Kitt Foon for procuring the photos of Platymma tweediei for us.
The images used herein to illustrate the game and its contents comes from ARK: Survival Evolved or from websites about it. Studio Wildcard holds the copyright to ARK: Survival Evolved.
About the authors
Dr. Rodrigo B. Salvador is a biologist specializing in the study of land snails, who – as some would argue – spends way too much time playing video games. He hates survival games but somehow always ends up playing them for a bit. Would that just be an exercise to confirm the hypothesis that he hates the genre?
Rafael M. Rosa is a biology undergraduate student interested in zoology, with a particular emphasis on animal evolution and systematics. He also likes video games and has been playing them for many years now, although most of his time is spent on grand strategy games nowadays.
Fernanda S. Silva, MSc., is a biologist specializing in land and freshwater snails, interested in scientific dissemination, and an admirer of games but unfortunately without much practice in them.
Daniel C. Cavallari, MSc., is a biologist and taxonomist specializing in land and marine snails. He is also a passionate shell collector and gamer who loves survival games (especially horror). ARK isn’t really a horror game, but he wonders if watching everyone defecate everywhere could be classified as horror.
 The game’s name is actually stylized as ΛRK. That’s a formatting nightmare, though, so we’ll stick to regular letters here.
 The Nintendo Switch version has a dismal metascore of 29.
 All the in-game information presented here was gathered from the Official ARK: Survival Evolved Wiki.
 In Latin, the word ‘limus’ means ‘slime’ and ‘segnis’ means ‘slow’.
 Another “famous” snail in fiction whose mucus is valuable is the flail snail, from the tabletop RPG Dungeons & Dragons. According to Volo’s Guide to Monsters (Wizards of the Coast, 2016: p. 144), a flail snails “leaves behind a shimmering trail that quickly solidifies into a thin layer of a nearly transparent substance [that] can be harvested and cut to form window panes of varying clearness. It can also be heated and spun into glass objects of other sorts. Some humanoids make a living from trailing flail snails to collect this glass.”
 There is a genus closely related to Achatina that’s called Archachatina. That would be a 20% cooler name for a species from ARK. If only the game designers had delved a bit more in Wikipedia… Anyway, the prefix ‘arch-’ means ‘chief’ or ‘principal’, like in the words archbishop, archangel, archfiend, etc.
 Despite that, some freshwater snails have also evolved lungs, providing a way to obtain oxygen even when they live in low-oxygen waters. An example of this are the apple snails (family Ampullariidae), which are popular aquarium pets.
 Sometimes classified as Lissachatina fulica, depending on whether Lissachatina is considered a subgenus of Achatina or a full-blown genus in itself.
 International Union for Conservation of Nature.
 Excluding the Aberrant and Eerie variants.