Tuesday 8 June 2021

D&D Monsters: Carrion Crawlers and Purple Worms

The majority of giant invertebrate monsters in the early editions of D&D are, at least in general terms, arthropods - the group of jointed-limbed creatures with chitinous exoskeletons to which insects, spiders, and crabs belong, among others. Exceptions include giant octopuses and giant squid, which are at least partially based on real animals, a few aberrations that are difficult to ally with anything real, and, somewhere in between, the purple worm. As originally drawn, the carrion crawler also qualifies, although this changes in later editions.

The worm-like body plan is a common one among real-world invertebrates, being found in a wide range of creatures that aren't all that closely related. But, on the whole, they aren't very fearsome, and the different types don't have the recognisability factor that spiders, scorpions, praying mantises, or whatever, might have. Even in D&D, the primary threat from the purple worm comes from the fact that it's just really big. The carrion crawler is a different matter, but, then it is rather less wormlike. Both creatures have 'Ronseal' style names, although, at least to my mind, 'carrion crawler' is, like 'mind flayer', one of the more evocative ones.


1E

The original carrion crawler is said to resemble a cross between a cephalopod and a cutworm (a kind of caterpillar), but the picture makes it clear that these are vague analogies, used for lack of anything better rather than an accurate description of what the thing is. The body has ten segments, covered with a leathery green hide, rather than a chitinous exoskeleton. Each segment bears a pair of unjointed, tentacle-like legs, confirming that it's not an arthropod - they're said to end in claws, but in fact, seem to have a pair of blunt toe-like lobes. Each segment also has a pair of red or yellow projections from the upper surface, which might be intended to resemble the hair clusters seen on some caterpillars (although not cutworms); their function is unclear and they disappear in later editions.

The head only resembles a cephalopod insofar as it has eight tentacles arranged around the mouth, similar to the arrangement of a squid - although that, of course, has ten tentacles, not eight. But, unlike that of a real cephalopod, the head is armoured and has compound eyes.
 
The purple worm, of course, has a much simpler body form. It is a long segmented worm, perhaps somewhat like an earthworm, but with a scorpion-like sting on the tail, a wide circular maw lined with teeth, and a pair of compound eyes. The text says that it is comparatively short, being only about five or six times as long as its body width, but the picture shows something much more slender, and probably about twice the stated length, at around 100 feet (30 metres).

Both creatures are unintelligent, getting the same 'zero' rating that most giant invertebrates do. The carrion crawler is, however, social in the sense that groups of them are often seen together, perhaps clustering around the same food source.

2E

Carrion crawlers are less inclined to live in groups in 2E, although it's not unknown, and when they do, they are generally aggressive towards one another. Allegedly, young carrion crawlers are a 'favourite' food for the larger adults. True, some real-world creatures do turn cannibalistic from time to time, but eating each other as a favourite food does seem rather maladaptive...

The creature shown in the illustration does, unlike the 1E version, appear to be an arthropod. This is because it has twelve pairs of jointed insectile limbs, albeit with a long gap between the anterior and posterior sets that serves no obvious purpose. The body is also much more caterpillar-like than before, with visible spiracles on some of the segments. It looks to have a pair of arthropod-like palps below the tentacles on the mouth, and it has switched from green to pale yellowish-tan.

The purple worm has subtler segmentation than before, with only the spiracles down the side of the body giving a clear hint as to the internal structure. The eyes are smaller, and the teeth larger and projecting forward. The described size and dimensions seem to fit rather better with the picture this time, too.

3E

The creature shown in the carrion crawler picture is completely different from that in the earlier editions. It's back to being green again, and the text says it's segmented, but there's little sign of that externally (as is true of some real-world animals). The limbs are simple parapodia-like structures, each ending in a single sharp claw; the one in the picture has thirteen pairs, but these may increase in number as it ages. Perhaps more significantly, the tentacles now all arise from the lower jaw, instead of surrounding the mouth, there are a pair of large grasping mandibles (they can't be useful for chewing, since they wouldn't meet in the middle, but holding a food item would work), and the eyes are on stalks, and no longer compound.

In accordance with all this, the carrion crawler is here described as an 'aberration', a term used for particularly alien creatures. Its intelligence has improved, albeit only to about the level of most reptiles and fish, rather than mammals, and it has a much thicker hide than it used to.

The purple worm has changed, too. It now has a keeled body with thick lateral ridges, and the segments are covered in heavy armour plates, rather than leathery hide. The mouth is more complex than before, with horizontally opening jaws and mandible-like flaps on either side that seem somewhat unnecessary given its style of feeding. It no longer has eyes and, like the carrion crawler is both slightly more intelligent, and considerably better protected by its armour, than in earlier editions. (It also has about three times as many hit points, but this is due to changes in the system, not to its inherent nature).

5E

The carrion crawler switches back to the colour of 2E here - perhaps there are multiple species. It has a fat body with indistinct segmentation. The hide is closer in thickness to the earlier editions, although there is no extra armour on the head. Each segment has a pair of limbs, without the mid-body gap; the limbs are jointed in arthropod fashion, but end in simple spikes and are vestigial in comparison to those of most adult arthropods - although, apart from being far more numerous, somewhat similar to those of caterpillars. 

The head retains the grasping mandibles of 3E, but adds a double row of teeth inside the mouth, a pair of insectile antennae and large eyes on the side of the head that don't seem to be compound. As in 3E, but not the earlier editions, it attacks by flailing its tentacles at a single target, rather than being able to strike with each one separately, which seemed a tad extreme. It's no longer an aberration, and now merely a 'normal' monstrosity.

The purple worm is somewhere between the 3E and 1E versions in its appearance. The segments are still covered with the very thick hide of 3E, and it is similarly eyeless, but the body is more circular in cross-section, with each segment having three spikes projecting from it, presumably to aid in traction as it burrows. The jaw does open horizontally, as in 3E, but the structure is simpler, without the side-flaps.

The carrion crawler varies in appearance more than most other "standard" creatures in the course of the game's various editions. But we can still make some suppositions about it.

The 1E version cannot be an arthropod, since it lacks the jointed limbs that are characteristic of the group. The closest analogy might be a velvet worm - a sort of soft-bodied vaguely centipede-like animal that has some features in common with arthropods anatomically but is clearly distinct. But, in any event, ignoring whatever the heck the 3E/4E version is, the ones shown in 2E and 5E do seem to be arthropods, and we can generalise to their anatomy in the same way that we can for ankhegs and the like.

If this is the case, it might be neotenic, retaining what should be a larval form into adulthood, so that it looks more like a caterpillar or maggot than like, say, an insect. Obviously, that's hard to say, in the absence of any identifiable creature, larval, or otherwise, that it specifically looks like. But the internal structure of caterpillars and the like is not that different from adult insects, so it makes little difference either way. Most of the general arthropod features will likely be present: a nerve cord running down the centre of the animal's underside, a tubular heart running down the back, excretory organs that open directly into the bowel, thus avoiding the need for a separate opening, etc. 

Like other giant arthropods, it also requires lungs, probably with openings on the sides of the body, rather than the head. Being land-dwelling, it probably lays eggs, although it's worth noting that velvet worms give birth to live young, just to be different.

The purple worm, however, is a different matter. Although the worm body form is a common one, the purple worm is segmented, and this implies that it is a form of giant annelid - the group to which the true 'segmented worms', including earthworms, ragworms, and leeches (among others) belong.

One of the distinctive features of an annelid's internal anatomy is that it's repeated along every segment. Thus, each segment has the same set of nerves and ganglia, the same arrangement of blood vessels, a single pair of excretory organs, and so on. The main nerve cord, like that in arthropods, runs along the underside, wrapping around the throat at the front end to form something that's as close to a brain as such an animal gets. There are two main blood vessels, one running down the back, and the other close to the nerve cord. The hearts, if there are any (and a big animal would need some) are up at the front, often as a set of four or five pairs of repeated organs connecting the main blood vessels.

The gut is basically just a long tube, with the anus being, unsurprisingly, on the final segment. In the purple worm, this segment must also include the poison glands, since it carries the stinger. There is no liver, with its function being taken up by tissue around the outside of the gut, and not much in the way of other organs, apart from the gonads. Some annelids do have eyes, and even compound ones, as shown in 1E, but the eyeless pattern of 3E onwards is more typical of the burrowing, air-breathing sort of annelid, rather than the ones that swim freely in the water.

While aquatic annelids often have external gills, the terrestrial ones simply breathe through their skin. This is possible because the skin is soft and moist, and the animal's body is extremely narrow, so it doesn't take much to oxygenate the blood. Neither of these are true of purple worms, which therefore, as with giant insects, require some sort of lungs. Most likely, there's a pair in every segment, with spiracles down the side of the body - something visible in 2E.

Internally, each of the segments of an annelid is separated from those on either side by a membrane, dividing the body up on the inside as well as visibly on the outside. Through the use of muscular contractions, this enables the animal to move by peristalsis - a sort of hydraulic system. That only works if the outside of the body is flexible, which it clearly isn't in the more armoured versions of the purple worm. A snake-like crawling motion is therefore more plausible, and, indeed, is found in some real-world annelids.

The body wall of an annelid is made of collagen, rather than the chitin of insects and lobsters, which fits with the impression of it being like really tough leather given in at least some editions.

A notable difference between purple worms and real-world annelids, however, is the head. In real annelids, the mouth is in the second segment, with the one in front of it being a blunt structure called the prostomium that contains a limited number of organs. (Indeed, it is often argued that it isn't really a 'segment' at all, even if it looks like one from the outside). Purple worms clearly lack a prostomium, with the mouth occupying pretty much the whole of the first segment, perhaps with a minimal brain wrapped around the throat just behind it. It's a plausible enough arrangement, just not one we really see on Earth.

All land-dwelling annelids lay eggs so it seems likely that purple worms do too. The exact mechanism must be different, however, because the structure that makes the cocoon within which the eggs are laid (the bulge-like thing partway down the body of an earthworm, but also found in, say, leeches) clearly isn't there. Most land-dwelling annelids are also hermaphroditic, but, given all their other differences, this doesn't necessarily apply to purple worms. 

But there's no reason why it shouldn't, either.

The signature attack of a purple worm is basically the fact that it's large enough to swallow humans whole... which doesn't require much explanation. The carrion crawler, however, has paralysing venom coating its tentacles.

Quite what the point of this, from the perspective of the carrion crawler, is debatable. It's perfectly happy to eat dead food - that's where it gets its name from, after all - so you'd think that just killing victims would be far more effective than simply paralysing them. But there we are.

In the real world, there are a small number of toxins that will paralyse someone through skin contact alone, although the vast majority require some sort of injection. However, none of them work anything like as quickly as the sort we see in D&D. 

Furthermore, in order to work as stated, the dose would have to be very carefully controlled. This is because real-world paralysing venoms and poisons (such as curare) run a high risk of being lethal. Simply put, if you're going to paralyse the muscles of the body, you're going to tend to stop the muscles that work the lungs from doing their job... and that's assuming you don't just stop the heart. At least with tetrapods, such as humans, a poison that completely paralyses is pretty much the same thing as a poison that kills.

Which is to say, you may well survive and recover, depending on the dose, but it isn't guaranteed, and poisoning and paralysis are not as distinct as the (necessarily simplified) rules make out.

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