Breaking The Symmetrical Mold: Can Animals Without Bilateral Symmetry Be Viable?

[This is part of a series of posts about animals. To find other posts in this series, see here.]

When designing your build in Outside, there are some pretty important choices you have to make that often don’t get nearly as much focus as they probably should. One big choice that most game guides tend not to talk about much is the choice of whether to spec into symmetry, and if so, what kind. This is something that I think deserves more attention, because it’s a decision that has huge implications as to what kinds of strategies and investments will work with your character. By far the most common choice is to spec into [Bilateral Symmetry], but there are a number of other interesting options worth exploring.

Before discussing the alternatives to bilateral symmetry, it’s probably worth talking a bit about what bilateral symmetry is and why it’s so popular in the first place. Bilateral symmetry means that the body of an animal is divided into a left half and right half, each of which is a mirror-image of the other. The main advantage of this is that it allows for maximal manoeuvrability. The physics engine of Outside is designed so that in order to change direction quickly in water, a build has to be able to push against the water, exercising a force in the opposite direction of the one they want to move towards. More specifically, this force has to be sufficient to overcome the resistance of the air or water. There are four variables that influence the magnitude of this resistance on a build: the density of water, the area of the portion of the body oriented in the direction of motion, the speed at which the build moves, and the drag coefficient, the last of which is based on the build’s shape. Having only one plane of symmetry means that bilaterally symmetrical builds can change their effective area and shape in such a way as to minimise the drag force they have to overcome, making it much easier for them to change direction quickly. On land, water resistance is replaced by gravity as the main force players have to overcome, and bilateral symmetry is even more essential as it’s necessary to balance the weights on each side of the body. Basically, bilateral symmetry is a prerequisite to any kind of mobility-based build, which is the biggest reason why about 99% of animal players spec into it. However, that still leaves about 1% of players who don’t care for the added complexity that fast movement adds, and stick with slow-moving, non-bilaterally symmetrical builds. It’s time now to take a look at what kind of strategies they use instead.

ALTERNATIVES TO BILATERAL SYMMETRY

• RADIAL SYMMETRY

If you’re fine with not being able to move quickly, there are three main alternatives to bilateral symmetry that you can choose from. The most popular alternative to bilateral symmetry is [Radial Symmetry]. To unlock radial symmetry, you have to pick a central axis for your build, and then create a pattern which repeats around the axis such that you can cut your build through the centre to divide it into several identical pieces. The number of pattern repetitions varies depending on the build, but is usually between four and eight. This is generally the best of the three options, because it does a lot to mitigate the main drawback of avoiding bilateral symmetry. The repeating patterns of a radially symmetrical animal’s body mean that it has an equal number of sensory organs pointed in all directions, so radially symmetrical animals never need to turn around in order to find food or watch for threats. This is a vital advantage for builds that can only move extremely slowly, if at all.

Radially symmetric builds: Cnidarians

The poster child for radially symmetrical build design in Outside is the cnidarian faction. This is one of the oldest animal factions in the game, having first appeared in the Ediacaran expansion, around 580 million years ago. Today, the cnidarian faction contains over 9000 builds, including some of the most iconic and ubiquitous builds of the ocean meta, like jellyfish, coral, and sea anemones. What accounts for their enduring success?

Like all non-bilaterally symmetrical builds, cnidarian players have to deal with the challenge of finding food and avoiding predators in a meta where almost everything else is faster than they are. Cnidarians solve this problem with their signature ability, [Cnidocyte]. The cnidocyte is a special cell containing a large, fluid-secreting organelle called a cnidocyst. Cnidocysts are divided into two kinds depending on their function: there are spirocysts, which secrete small sticky hairs to entangle prey, and nematocysts, which are filled with venom. In order to coordinate the cnidocytes’ firing, cnidarians have chemical sensors to detect living organisms, as well as organelles called cilia on their stingers that respond to touch. When the chemical sensors detect chemicals associated with life, the cnidarian gets ready; if the cilia feel a touch just after this, then the cnidocyte fires and injects its venom. Each cnidocyte can only fire once, and it takes them about two days to regenerate all the lost cnidocytes after a sting, so it’s important that they have two different signalling systems working in conjunction to ensure they only sting at just the right times.

Players used to maining complex bilaterian builds are often shocked when they try out cnidarians for the first time by how comparatively simple the designs and gameplay are. Cnidarians don’t have nearly as many organs as bilateral builds do, probably because their inability to perform rapid movements means that they don’t need as many body parts to coordinate their gameplay effectively. While they do have a very simple digestive system, cnidarians don’t have respiratory systems; oxygen just gets absorbed directly into their cells with no need of any special organs to facilitate breathing. Cnidarians also don’t have hearts or any kind of blood. They do have a small stomach where food gets coated with digestive enzymes, but once it’s digested, the nutrients just diffuse from the cavity into the rest of the body. Due to their simple anatomies, cnidarians don’t need a muscular pump to power this diffusion process the way most animals do.

There’s one other major thing missing from the cnidarian anatomy compared to bilaterians, which constitutes probably the biggest disadvantage of the build aside from their low mobility: cnidarians don’t have brains. They have a few sensory neurons, which are enough to control a few simple reflex actions, but they’re mostly disconnected from each other; there’s no central organ coordinating their responses. This is actually a weakness that’s common to all non-bilaterally symmetrical builds; you have to unlock bilateral symmetry before you can start speccing into a brain, and hence into any intelligence beyond basic reflexes. This is probably because bilaterally symmetrical animals have an identifiable front end, which tends to be the part that goes first whenever they move. This makes it a natural place to put all the major sensory organs, so that the build can collect as much information as possible about the things it’s moving towards. Once you’ve formed a head with all your sensory organs, it then becomes a natural decision to place an organ inside which can gather all of the sensory information, interpret it, and send response signals to the rest of the body. Radially symmetrical animals, on the other hand, have sensory organs evenly spread out all over their bodies, so there’s not really any efficient way to connect all of them to a single, central coordinating organ.

While cnidarians may be lacking in mobility and intelligence, one area where they excel is in HP regeneration. Cnidarians can regenerate from just about any injury – a hydra polyp only needs a few days to regenerate into a full, healthy animal after being separated into its component cells. At least some cnidarians take advantage of their radial symmetry to accomplish this: jellyfish, for instance, can rearrange their own body parts following an injury in order to regain a symmetrical form, allowing them to heal from injuries without needing to take the time to grow new body parts.

Radially symmetric builds: echinoderms

While cnidarians unlocked radial symmetry long before anyone had figured out how to make bilateral symmetry work, there’s another faction in the game that started off as a bilaterally symmetrical group until the players quickly decided they’d rather try to copy the cnidarians. This group is called the echinoderms.

Echinoderms are interesting because in addition to the guild overall having shifted from bilateral to radial symmetry over the course of evolution, each individual player goes through the same transformation over the course of their playthrough. All echinoderms start off as bilaterally symmetrical, free-swimming larvae. As they get older, their left side starts growing larger than their right side, and eventually absorbs it completely, turning them into a five-part, radially symmetrical form.

Echinoderms first appeared in the Cambrian, around the same time as most of the other major factions. Today, they’re one of the most popular factions for deep-sea players, and have over 7000 builds to choose from, of which the best-known are the starfish, sea urchins, sand dollars and sea cucumbers. While their lack of brains and lack of strong mobility still make their gameplay simpler than most bilaterally symmetrical animals, their build designs are a bit more intricate than those of cnidarians, as their unusual evolutionary process has left them with a number of unique adaptations. First of all, echinoderms have a skeleton-like structure underneath their skin, which is composed not of bone, but rather of calcite-based plates called ossicles. These plates are porous and spongy, so that they don’t weigh the animal down too much. Their purpose is to help echinoderms remain upright by providing structural rigidity, and also to deter predators by being very hard to digest. Another unique adaptation of echinoderms is the trait [Catch Connective Tissue]. Almost all animals have some form of connective tissue in-between their other tissues, but this connective tissue generally has a fairly constant stiffness which only changes as a result of ageing. Catch connective tissue, on the other hand, can rapidly alternate between rigidity and flexibility in response to the stimulation of nerves. This is why starfish seem soft and flexible when they’re crawling on the seafloor, but become rock-solid when you try to pull them out of a crevice.

Like cnidarians, echinoderms have no brains or hearts, but unlike cnidarians, they still have circulatory systems. More specifically, they have a unique type of circulatory system called the [Water Vascular System], which consists of a network of fluid-filled canals with small projections called tube feet on the ends. In order to move, echinoderms alternately contract muscles that force water into the tube feet, causing them to extend and push against the ground, then relax them to allow the feet to retract. These contractions can’t generate fast movements, but they can still produce a stunning amount of power, as you can observe when a starfish latches onto a mussel’s shell and pries it open. The flow of water through these canals also plays a role in a number of other bodily functions, including respiration, digestion and sensory reception.

Despite their low XP value and indigestible ossicles, echinoderms are frequent targets for predators because their low mobility makes them easy to attack. Their defences against this vary depending on the build, with spines and toxins being the most popular choices. While not quite to the extent of cnidarians, echinoderms still have pretty impressive HP regeneration, and some of them take advantage of this to distract predators via autotomy. I don’t have space to go into all the different varieties of echinoderm and their strategies here, though, so I’ll probably have to expand on this more in a later post.

Radially symmetric builds: overall evaluation

While I would generally recommend players stick to bilateral symmetry, I’d say that radial symmetry is a pretty clear second-best option. Having no brain and not being able to move quickly are definite disadvantages, but if you spec them right, radially symmetrical builds can still be pretty impactful in the meta. Coral, jellyfish, and starfish are some of the best examples of highly successful radially symmetrical builds. Of the two major radially symmetrical factions, I’d say echinoderms rank slightly higher, since they at least have some ability to move under their own power. It’s hard to tier entire major factions containing thousands of varied builds, but if I had to, I’d probably say cnidarians place around low B tier on average, with echinoderms averaging around high B tier.

• BIRADIAL SYMMETRY

Biradially symmetric builds: ctenophores

Due to their abysmal mobility and intelligence, radially symmetrical builds tend to go with fairly simple designs and game plans compared to bilaterally symmetrical builds. But that doesn’t mean cnidarians and echinoderms are the simplest builds out there. If both bilateral and radial symmetry are too mainstream for your tastes, you can join the ctenophore faction, which takes an in-between approach called [Biradial Symmetry]. Just like radially symmetrical builds, biradially symmetrical builds have a central axis around which their body extends in a symmetrical pattern. However, while radially symmetrical builds have patterns that can be divided in a number of ways and still produce two identical halves, biradially symmetrical builds can only be divided in two such ways. In the case of the ctenophores, you can divide them into two mirroring halves either by splitting them through the middle of the pharynx or through the middle of the tentacles.

Ctenophores’  bodies consist of a mass of jelly, with a jelly layer two cells thick on the outside, and another jelly layer on the internal cavity, hence their alternate name, comb jellies. Although jelly doesn’t show up well in fossils, there actually are intact game logs showing ctenophore activity as far back as the Early Cambrian, around 520 million years ago. Interestingly, Cambrian comb jellies were actually a lot more complex and varied than modern forms, but they’ve undergone a gradual simplification over the course of their evolution.

Comb jellies are pretty similar to actual jellyfish in both appearance and gameplay, but they have a few key distinguishing traits. The first is their method of movement. Comb jellies swim using little organelles called cilia. The outer surface of a ctenophore is coated with eight rows of cilia, called swimming plates, which run from near the mouth to the opposite end, and are spread out roughly evenly around the body. Across each row are plates called “combs”, which each have thousands of very long cilia, and the cilia beat rhythmically so as to propel the comb jelly’s body away from the mouth. While most eukaryotic organisms have cilia on their cells, comb jellies are the largest organisms that use their cilia to move around – larger animals generally use them only for sensory reception.

Like actual jellyfish, and most other cnidarians, comb jellies are almost all predators. However, instead of the cnidocytes of true jellyfish, the tentacles of a ctenophore are filled with unique structures called colloblasts. Colloblasts behave very similarly to cnidocytes, but instead of being filled with venom, they’re filled with adhesives that cause prey animals to become stuck to the ctenophore’s tentacles. Ctenophores typically hunt by hanging motionless and near-transparent in the water, using their tentacles as stationary traps, making them a little bit like the marine equivalent of spiders. Once they’ve got an animal stuck to their tentacles, they bring it to their mouths and swallow it. Once swallowed, it gets liquefied by the secretion of enzymes in the pharynx and by pharyngeal contractions, and the resulting slurry gets drifted through a system of internal canals to nutritive cells, which digest it. Ctenophores most commonly prey on zooplankton, and are one of the main predators of planktonic crustaceans.

As with the radially symmetrical animals, ctenophores don’t have brains or central nervous systems. Instead, they have a cobweb-like ring of nerves extending outwards around the mouth. Their nervous systems are even simpler than those of true jellyfish, as they lack the capacity to produce many neurotransmitters found in the nervous systems of all other animals, including serotonin, dopamine, and noradrenaline. In fact, it’s been speculated that the ctenophores have the exact minimum requirements for an animal to have a functioning nervous system at all.

If I’m being honest, I don’t see much reason to play as a ctenophore in the current meta. In addition to the low mobility and intelligence common to all the builds on this list, ctenophores also suffer from an abysmal defence rating. Many ctenophore builds are so fragile that data-miners only know about them from photographs and writers’ notes, as they fall apart whenever someone tries to capture them for scientific study. This is more of a problem for open-ocean varieties, as coastal varieties need at least some resilience to withstand the tides, but I still don’t see much reason to play as them when spiders and true jellyfish use essentially the same strategies with far more success. It’s not really surprising to me that the ctenophores are one of the smallest major factions nowadays, with fewer than 200 remaining builds – less than 2% of what the cnidarians have. I’d probably rate the ctenophores around the lower end of D tier, and even that seems pretty generous.

• ASYMMETRY

Asymmetrical builds: sponges

If even biradially symmetrical builds are too complicated for you, it’s possible to go even simpler. If you want a build so simple that it will let you AFK your entire playthrough and still collect XP, look no further than the sponge.

Sponges are quite possibly the oldest animal faction still in the game. The earliest game logs showing sponge player activity go all the way back to the Ediacaran, over 550 million years ago, and their design remains one of the most primitive among animals. While the above-mentioned builds are all missing brains and hearts, sponges go even further by lacking organs and tissues altogether. All they have are bundles of cells, each of which is undifferentiated and can transform into any other. The insides of their bodies are filled with channels that water flows through, and their shapes are generally designed to allow this flow to be as efficient as possible. With a few exceptions, this generally doesn’t involve any kind of symmetry.

Sponges get food using a filter-feeding strategy, continually straining bacteria and other oceanic microorganisms out of the water. These microorganisms get captured by the sponge using pores called ostia. Microbes of about half a metre or smaller get trapped in the pores and are consumed by cells called pinacocytes and archaeocytes that extrude through the cell walls, while even smaller microbes pass straight through the pores to be consumed by cells called choanocytes. Archaeocytes package the food they capture in structures called vesicles and carry it through the body to feed cells that can’t digest food directly.

Being even more primitive than the radially and biradially symmetrical animals, sponges have no mobility at all, and lack any kind of nervous system, not just a brain. In order to survive under these conditions, they’ve needed strong passive defences to deal with predators. Most sponges have an internal skeleton composed of a gelatinous substance called mesohyl, and this is often stiffened by silica shards called spicules. These spicules are difficult to eat, and act as a deterrent to predators, similar to the echinoderm ossicles discussed earlier in this post. Some sponge builds shed spicules regularly to create dense carpets of sharp glass around them, preventing sea-floor-based predators from even going near them. There are also some sponge players that take a more conventional route to passive defence by just speccing into poison.

From a certain point of view, sponges are one of the most successful factions in the game’s history, having kept more or less the same strategy viable in ocean biomes for nearly as long as animals have existed. But in spite of their strong abilities, it’s difficult for me to see them as high-tier when they have so many obvious drawbacks, like having no mobility, no intelligence, and no attacks of any kind. I’d say that their tier rating is around a C at most.

Asymmetrical builds: Placozoans

Sponges are about as simple as it’s possible for an animal build to get while still being reasonably successful in the meta. But if, for some reason, you insist on going even simpler, you can try out a placozoan build. These are the simplest animal builds in the entire game. Like sponges, they have no tissues, no organs, and no symmetry; their entire bodies are just an outer layer of compactly packed cells with cilia for moving, with a loose sheet of star-shaped cells inside. They feed by engulfing small particles of organic detritus through the lower surface.

Placozoans are so primitive that they not only have no symmetry, but no definite shape at all – their outlines are in perpetual flux. If I’m being honest, I have no idea why anyone would want to play as a placozoan build. They basically seem like an attempt to make an animal without getting any of the benefits of being an animal, and I don’t know why you wouldn’t just play an amoeba or bacterium instead. The placozoans are pretty boring and frankly useless gimmick builds, and I rate them in F tier.

CONCLUSION

The above list covers all the alternatives to bilateral symmetry available to animals. Spherically and icosahedrally symmetrical builds are also available, but finding them requires you to look at non-animal factions, like plants and bacteria. I think it’s fair to conclude from this that the 99% of players who opt for bilateral symmetry are making the right choice – there isn’t a single non-bilaterally symmetrical build that I would consider to be top-tier. However, if you insist on taking a heterodox route, radial symmetry does have real potential, and both of the major radially symmetrical factions tend to do better-than-average in the ocean meta. Those really are your only viable options, though; the few builds that have neither bilateral nor radial symmetry are all in a pretty weak position in the meta. I hope this was helpful.