If somebody asked you to draw a spider, how well would you do? I guess you would do the legs right, maybe even get the body parts in place – chest and head together as one blob, fat abdomen as another. But unless you’re a specialist, you won’t get the mouth right. Don’t worry though, by no means are you alone here. If there is one thing movie and game creators get consistently wrong about spiders and insects, it is how their mouths work. If nature was the way most people imagine it, it would be possible to French kiss a tarantula. Assuming you’re of the same size. And assuming it is consensual – which might be problematic, since courting is a tricky business in spiders.
Our view of nature is very mammal-centric. We judge the entire animal kingdom from the tiny county of cute furriness that wears a common face with one pair of eyes, soft nose and a mouth full of pointy white teeth. That mouth is surrounded by fleshy pouty lips and inside that mouth there is a wet soft tongue. If a creature doesn’t wear that face and boasts multiple eyes and some chitinous machinery instead of lips, it is a freak. Plain and simple. However, if we suspend our judgement and give our arachnophobia a good kick it deserves, we will discover the twisted road that led us to have a mouth we like, and the plethora of other designs a mouth can have.
Let’s start with us. How did we and our mammal kin happen to have all that white and pointy cuteness we show each other so often? While we’re not the only animals to have teeth, mammals have designed the hell out of them and made it their shtick. Other vertebrates, like reptiles, have rootless teeth that are usually the same no matter where in the mouth they happen to pop. On the other hand, ours have strong roots and serve different functions: molars crush, canines rip and incisors, well… incise. Some mammals lack one or several of these types, for instance horses don’t need to rip meat and therefore don’t have canines. These types aren’t interchangeable and have a fixed position in a jaw of a mammal, and of the three groups, molars are the most important one.
You see, a usual tooth of a vertebrate animal not only lacks roots, but also any kind of architecture and is essentially pyramid-shaped. Our grooved molars are the result of millions of years of evolution, with our ancestors in the Cretaceous and Jurassic periods trying out every possible shape from three-pronged ones to something that looks like an exploded pinecone. When the dust settled, we got our efficient groovy molars. The same way it took several centuries of gothic script for humans to finally settle on Times New Roman.
With the exception of teeth, our amphibian and reptile cousins share the basic elements of mouth design with us. It is pretty safe to conclude that you can definitely French kiss any reptile, conditions allowing. Maybe their lips aren’t that pouty, maybe their tongue is sometimes forked and sometimes is capable of reaching out and grasping a fly from air, but heh, giraffes have prehensile tongues too and can pick their noses with them (you should check the photos).
Things start looking weird though when we get to fish. Not only do some fish have teeth all over them (and I do mean all over them – we’ll get to it in a second), but they can even have multiple jaws – like moray eels, which use one jaw to grab the prey and another to move it further into their throat. What the hell is happening there? To get an answer to this question, we should rather ask “Why are we, mammals and reptiles, so disgustingly single jawed?”.
Our bony jaws have evolved from gill arches – the things that support gills in fish. That is because their initial function wasn’t that of food processing, but merely to force more air through. We don’t have gills, we use sophisticated machinery to pump air into our lungs, and so we’re basically left with what’s most efficient. Times New Roman of jaws. Our gill arches became our throat and – randomly – inner ear. In contrast, fish still have a full collection of them and aren’t afraid to modify some into an additional bear trap.
Keeping that in mind, how many tongues do you think a typical fish has? Can you French kiss a salmon? As it turns out, not exactly, since they don’t have tongues at all. Tongues evolved from the muscles that fish use to move their gills, and though fish might have found a use for a tongue, they don’t have muscles to spare to turn into it. Besides, when you’re in water, ingesting food is much easier – everything you eat is basically some kind of soup. Fish do, however, have a small fold at the floor of their mouth, but the only function of it that I am aware of is that it gets eaten by a crustacean parasite, that then itself acts like a tongue. You can definitely kiss that.
So basically the “true” tongue appears when our adventurous frog-like ancestors climbed out of the water. The “true” jaws precede them by a bunch, and appear once fish evolved enough gill arches to spare. So what did those pre-jaw guys look like? And – most importantly – did they have teeth? The short answer – more than you do. For originally teeth weren’t used for food processing. They weren’t even in the mouth. They were a type of scales, a plate armour.
Long before a trout invented its rainbow coating, a coat of teeth was the top of the pops. In fact, it is so good that some creatures have it still – you call them sharks. Shark scales are basically teeth; they are made of the same material called “dentin” and have pulp with blood vessels in the middle and a strong enamel coating on the outside, which makes them the perfect armour. It is exactly that ability to withstand harsh conditions that allowed teeth to find their way into our mouths – quite literally so. For millions of years they slowly migrated further and further inside the mouth, until they found their place on the gill arches, where they stuck ever since.
So… is that it? Does it mean, that any non-vertebrate animal doesn’t share anything common in terms of their mouth structure with us? Only a muscular hole at the top of their body and the fact that they put food into it? Well… How to put it… Not even that. Most animals have their mouth where we have our anus. Exactly. While you are bringing your gill arch from the floor, let me tell you this really quick: an animal is basically a piece of gut with some add-ons to make it happy.
The gut is the first thing an embryo develops. First it forms a closed gut inside itself, then it opens up to form a mouth. And in a lot of cases it stops there – quite a few animals poop from their mouth (and you thought that the image of French kissing a tarantula would be the most appalling part of this post, heh!). Most animals however go further and form a second opening on the other end and make in anus. Simple.
But we don’t like to be simple. We like to have tongues and complicated molars and other stuff. And we (animals with a spinal chord) basically perform a little developmental switcheroo on mouth and anus. It is slightly more complicated than that, but you got the idea. Only one group of animals does the same weird trick – Echinodermata, the group with starfish and sea urchins, and those guys are really weird. I mean like three nervous systems weird.
So, does it mean that you can’t French kiss a tarantula, cause not only does it not have tongue or lips, but you would be kissing what amounts to our anus, right? Well… ish. The issue is, whether you can call the structure that looks and acts as a tongue a tongue, or whether you call a tongue only that which evolved from the same tissue. If the former, then quite a few organisms would have tongues and teeth. Slugs even combine the two, and use tooth-riddled tongues to scrape food from stones, while guys like bobbit worms have huge teeth, so strong they can drag whole fish into their underground burrows.
And all of that explodes in terms of forms and flavours when it comes to arthropods and especially insects. Those guys have so many mouthparts we don’t have words for them and instead call them by number, like maxillipeds-1, maxillipeds-2 and so on. Most of those are actually legs that deformed and mutated through aeons of evolution to the point where whole conferences debate how exactly insect mouthparts evolved. In terms of mouth structures, no other group of animals can rival them. A telescopic grappler with teeth on it? They have it. A syringe? Check. A sucking pump? Check. A hose? Check. To illustrate the point, a honeybee’s mouth consists of: labrum, epipharynx, mandibles, maxillae (with maxillary palps, basically a sort of antennas) labium (with labial palps) and ligula which is – for all purposes – a tongue.
At the same time, unlike those of insects or crabs, the mouth of a spider is reasonably simple. It is a muscular hole with a single pairs of reduced maxillae, guarded by a pair of claw-like “chelicerae” and a couple of mini-legs, called “pedipalps“. They can be quite cute though (you should absolutely check out ogre-faced spiders).
So yes, in the end of this weird journey you can be reaffirmed in your opinion that under no conditions you would French kiss a tarantula. However, you can French kiss a honeybee. Only if it consents, obviously.