Crab Bag, Part 4: For Whom the Crab Tolls

We got into the legend of a miracle crab connected with the Catholic missionary Saint Francis Xavier and how that story connects loosely to a real species known as the Crucifix crab, and we got into a bit about questions of object carrying behavior in crabs. We talked about the family of crabs known as Raninity or FROs, and they's somewhat uncrab like. Elongated body shape crabs have a very

side to side kind of orientation. The Raninity have instead specialized for backwards burrowing by somewhat elongating their body front to back. We talked about a legendary type of monster crab from the traditions of the Lunda people of Zambia. A crab with two heads that attacks by eating your

shadow had some interesting hippopotamus properties as well. We talked about the idea of seeing faces in the shells of crabs, and in the last episode we read a bizarre and interesting eighteen sixty four letter to Scientific American which argued that the US Navy should construct a giant biomimetic attack submarine based on the model of the Atlantic horseshoe crab.

The letter writer called this the King Crab Warship, and this led into a general discussion about the sort of patent fever surrounding the US Civil War and Abraham Lincoln's surprising relationship with very eager inventors of every kind, and this ran the whole gamut from scammers and cranks to real innovators. And in that episode we also talked about the cultural significance of crabs in China, including getting into a short older report from Fujian of crabs being involved

in exorcism and protective magic. And then we also talked about the more common association in China between crabs and good fortune, wealth and luck, and got into a few other stories there, like the story of Bajied, the first man to eat a crab, which is a great distinction.

This is an episode in which titled a Taste of Freedom, one of my favorites, in which Zoidberg's people end up temporarily conquering the earth and they have this giant crab mech that also has a sand castle on top of it and these big claws for tearing things apart, and it is the mobile oppression Palace.

crabs by common naming convention. These are true crabs. They're brachurins. The family again, is ossipodidy. Not all occipodity are fiddler crabs, but all fiddler crabs are occipodity, and they are known for their sexually dimorphic trait of extreme claw asymmetry. So even if you've never read much about fiddler crabs before, you've probably seen a picture of one of these at some point. Among male fiddler crabs, one claw is way bigger than the other. It's not just bigger, it is

often absurdly comically bigger than the other. In extreme cases, the bigger claw is up to half of the male's total body weight. So for a rough analogy, imagine you know an average adult human male and one of his hands is normal, but the other hand is about four feet wide and weighs like eighty to one hundred pounds.

of central place in that series. I guess I'll start off by mentioning a few general observations about fiddler crabs before we get into the main claw research I wanted to talk about today. As I already mentioned, this huge asymmetrical claw is a sexually dimorphic trait, so you only see it in males. Female fiddler crabs have two smaller,

matched regular size claws. Fiddler crabs are burrowing crabs, so they nest in these little tunnels that they dig in the mudflats or in the sandy intertidal areas where they live. And exactly how the burrows are used varies between species, but usually they're involved in say brooding, you know, laying eggs or reproduction in some way, and the quality of the burrow defended by a male contributes to the male's success in mating. Fiddler crabs have a very interesting way

of eating. They use their front claws to shovel lumps of sand or mud into their mouthparts, and then their mouthparts rapidly dig around in this glob of sand or mud to find clean and extract any edible material like algae or bacteria or bits of dead other detrit us. This feeding process creates a very cute waste product. Actually, in a couple of sources I was seeing refer to

this as pseudo feces. I don't know if this technically counts as pseudo feces to a zoologist or not, but they're little leftover pellets of mud or sand that pile up around the fiddler crab's burrow. These are the pellets the crab has spit out after extracting food from them, to the extent that they are called pseudo feces there. This would be because they're not real feces that you know,

they haven't passed through the animal's whole digestive system. They're sort of what gets rejected by the bouncer at the entrance of the digestive system rather than what comes out at the end, though they do look like and are often mistaken for droppings, Hence they would be kind of false feces. Rob I've got a picture for you to look at in the outline here. I don't know why these these little diesel balls are cute to me.

You get all that out of there, you swallow it, and then you spit out a tidy little clod of soil that is left over, and then you just keep doing this over and over all day until you have a little mountain of spherical dirt clods piled up around your front door.

much completely useless for feeding. So if you watch female fiddler crabs eat, they will rapidly shovel mud and sand into their mouthparts with both claws in a continuous back and forth cycling motion. But because males only have the one normal sized claw, their ability to feed themselves is basically cut in half. It's like I've just got my one good eaten hand and then I've got this big hand, but I can't really use it.

this is a mighty weapon. You know, it makes the male that wields it incredibly hardy and healthy and fit. And while a big claw might often be a sign of underlying fitness, is not the cause of underlying fitness. It mainly comes with downsides to the crab's ability to survive the daily struggle for food. So not only does the claw greatly hamper the mail crab's ability to eat. It hugely increases the mail crab's food energy needs. So

you've got this big old claw. It's a heavy piece of tissue, so it increases the crab's based metabolism, and it also makes it more energetically expensive for the crab to move, to run around and move because it's carrying this thing. So you imagine if you had to live your life with an eighty pound suitcase surgically attached to your hand, that would kind of you would need to eat more food. It would just you know, cause a lot of trouble for everything else you needed to do well.

It might deter some predators, but research has found that birds like grackles, which prey on fiddler crabs, are actually more likely to target and attack males with big claws than they are to attack females or males with smaller claws. So a big claw means you're number one, easier for the predators to see, and also you are a more valuable prize because there's more meat inside you.

a couple of minor practical purposes. To start with the minor practical purposes, I've read that males sometimes use the large claw to kind of cover and shield the entrances of their burrows, so a large claw may provide extra defense in some situations there but by far the most widely recognized purpose of the large claw is in sexual competition and sexual signaling to appeal to female fiddler crabs and to intimidate and fight off rival males, especially in

competition for access to burrows and the quality of burrows is in part what appeals to females who are looking to mate. So when it comes time for mating, male fiddler crabs engage in a ritualized behavior known as waving, where they stake out territory in front of their burrows and they wave their big claw up in the air for all to see. Each fiddler species has its own specific waving pattern, and this waving behavior serves to intimidate rival males and drive them away from the area of

the crabs borough. A big claw so helps with this as well, you got a big claw, so it's like, oh wow, you know, don't want to mess with that guy. And as for appealing to females, the results are in and it turns out female fiddler crabs do like big claws, that's what they're into. Big claws are often taken as an honest signal of genetic fitness, for one thing, because they take a lot of energy to grow and sustain, so they are evidence that this crab must be eating well,

it's doing well, it's probably a good mate. And then also crabs continue to grow throughout their lives, so that means that bigger crabs tend to be older crabs. So a bigger claw usually functions as a somewhat honest indication that a particular crab is a survivor across many seasons.

authors called Dishonest Signaling in a Fiddler Crab. The authors of this paper start off by talking about how when animals exchange information with one another in situations in all kinds of situations like predator prey interactions, make choice and competition for resources, you would naturally expect to find some

evolutionary attempts at dishonest communication. So like, if we're always going to compare shoe sizes to decide who gets to eat this animal carcass, we both found it would pay biologically for me to find a way to make my

feet seem bigger than they actually are. On the other hand, there are some theories in biology that say, you know, you can't have too much cheating or dishonesty in information exchanges in nature, or the information exchange becomes unstable and it just like doesn't really work for this, Like if everybody's lying, then the signal just becomes unreliable and it's it's no longer useful biologically.

demonstrating cheating. Cheats are designed to go unnoticed. Even if you identify an individual with a disproportionately large signal for its underlying quality, it is unclear how you can differentiate this from natural variation in the relationship between signal size and male quality. However, in the fiddler crab species that they call Uca and ulypis now known as Ostrica and Ulypus, they argue that it is possible to identify a clear example of a dishonest sexually selected signal, and it goes

like this. When crabs lose a limb, they can often grow it back. You know, this is one of the advantages of being something like a crab. Mammals or not like this. We can regenerate some types of tissue, but if we lose a whole limb, it's gone. You know, it's not growing back. But crabs frequently lose limp due to attacks by predators or fights with rival males, and

grow new limbs in their place. So, according to the authors, when most filler crab species lose a claw, they regenerate one that is pretty similar to the original in form, But in a few species, including Ostrica and Alypus quote, males instead regenerate claws that are lighter, more slender, and less robust, which they call leptokilus than the original claus, which are called brachikilus. So again, Brachychelus means it's the

strong claw that the crab had originally. The leptokilis claw is the weaker, less muscled regenerated claw, they continue quote. For a given claw length, leptokilis claws have a smaller muscle mass than do brachykilis claws, and they may thus be weaker and less effective weapons. So these regenera did leptokilis clause match the original big claw in some ways. For example, they sometimes match it in length, but are

reduced in terms of strength and internal muscle mass. So they regrow a claw that looks big, but it is literally partially hollow, like, it does have muscles inside, but it's got less muscle mass inside than the original claw did. So if it actually came down to a real fight, this regenerated claw would usually lose. And the authors did

test this out. They staged some fiddler crab fights to make sure, and they indeed found that the Leptokilis males were significantly worse at fighting and lost in battle against Brackykilis males.

later kill you. So fighting is just something you want to avoid, even if you're probably going to win. So it's better for everybody involved if the competing males have a way of sizing each other up and deciding who would probably win the fight, allowing them to skip the fight altogether, so you know the likely loser, they have some kind of piece of evidence, you know, maybe horn size or in the case of crabs, probably claw size, They see the evidence of the likely winner's fitness, and

the likely loser just retreats before combat starts. Previous research in fiddler crabs has found that the main criterion that males use to assess each other's fighting ability is big claw length, which is not necessarily reduced to the same degree in the regenerated claw. The way that other measures like strength and internal muscle mass are also appeal to females seems related to assessments of claw length. Females of this fiddler crab species are looking for males with a

long claw, so how does this relate to regeneration. The authors of the paper set out to investigate whether in this species the weaker, partially hollow regenerated clause would serve as a dishonest but effective signal to win mating opportunities. Could males with these weaker claws bluff their way into competitive victory, control of burrows and into sects And the

answer is basically yes, the bluffing works. So one way of assessing the question is if males with strong original clause usually win fights against males with the regenerated clause, do the males with strong original clause seek out males with regenerated clause to dominate in bully or are they more likely to aggressively escalate to real fighting against males with regenerated claus. In this study, the answer was no. It really just doesn't affect choices about whether to fight or who to fight.

they convince females Yes? Quote During mate searching, females do not discriminate against males with low mass regenerated claws, indicating that they are deceived as to the true cost males pay to produce sexual signals. So it really seems like the the you know, the weaker claw is a very smart gamble. It is true, it's not as good at fighting, but at least within the species, it gets the important jobs of bluffing rival males and impressing females done quite well.

the author's right quote. Since Leptokilis claws have a lower mass than brachikilis clauseleptekilis males use less energy to wave at a given rate. Remember, the sexual display is waving the big claw in the air, so if you've got a claw with less muscle mass in it, it's easier to wave around, so you can actually show off more with a weaker claw. Quote. Thus, even when in relatively poor condition compared with Brakikilas males, Leptokulis males can wave

at the same rate. In biological terms, it's cheaper to make and maintain, and it's easier to use for their primary purpose, and it works just as well for most things, it seems like, so the real question kind of turns into why do the male fiddler crabs produce the original stronger claw in the first place, Like, why hasn't evolution just completely gotten rid of the strong claw and you know, just started making these weaker, more hollow claws because the

strong claw is very costly. It's a great burden to the crab. One thing that again is worth noting, is that if there is too much cheating or dishonest signaling within a population of animals, of course the signal loses its value, right, So that can be you know that the whole system can be destabilized by excessive deception or cheating.

But that doesn't necessarily explain like why the individual will you know, what would be against the individual crab evolving in that direction to just have the weaker hollow clause from the beginning. And so the authors do explore this a little bit. They say one difference is that since the leptokilis males are worse at actually fighting, they are somewhat more likely to lose their burrows in fights to be driven away by stronger males. The authors tracked this

behavior as well. They were like, what happens after this? What happens to both leptokilis and Brachikilus crabs after they're driven from their burrows and have to find a new one. The authors discovered that there was no major difference in how long it took them to find new boroughs, nor in the distance they had to travel, nor in the number of fights initiated in competition for burroughs. There was

a difference in how the crabs got new burroughs. So Brachikilus males more often got their new borough by fighting and driving out an occupant. Leptochilus males more often found empty burrows and moved in. But then again, does this really make a difference. The authors looked into it, and they found that the empty burrows that were occupied by the lighter clawed males were just as attractive to females and thus were no lower in quality than the occupied

burrows that were seized by fighting. Quote Hence, neither the process nor the outcome of searching for new burroughs seems to be more costly for Leptokilis than Brachykilus males. A higher frequency of borrow loss for Leptochilus males is the only cost that seems to favor the Brachykilis claw form, So the only difference they're finding is that when you have the weaker claw, you're more likely to lose your

burrow to be driven out. They say. Quote, small males are on average more often involved in fights since there are more males in the population that are slightly large than them. The increased benefits of having a brachykili's claw when small may therefore select for the initial production of this robust claw form. As males grow, the relative frequency of fighting decreases, and brachikille may be less advantageous. Moreover,

larger males spend more time waving. Something feels almost metaphorically interesting about this, So like, when you're young, you are more likely to have to fight for what you get or have to fight to defend what you've got, so

it pays to have the actual muscle inside. Because you're smaller, you look like a softer target, so you're to be you're going to be escalating to actual fights more often when you're younger, But as you get older and bigger and scarier, you can more often bluff your way out of fights. Thus the advantage of having a real fighting claw is reduced and starts to pay more and more to bluff and cheat with with with this weaker claw that is easy to wave around in the air.

till noon. There's there's sort of a principle that once you your reputation is already established, or you have some kind of you have some kind of appearance of prestige or having been established, you have to do less actual work or it will less often come down to you really proving your ability, and more often you can kind of bluff and cheat your way through situations because people are you know, you seem to be established, you are

more intimidating, andeople are less likely to question you, and so real ability to compete at whatever, real ability to do the thing tends to be much more important when you have less of a reputation already. Yeah, but it's also really interesting to come back to the idea of how of course, you know, systems of information exchange are always destabilized and eventually destroyed if there is enough lying within the system, Like information exchange doesn't work if everybody's lying.

So it is kind of surprising to me that there could still remain this type of sexual signaling, this type of information exchange based on claw size in populations that have rates this high of deception in them. That might you know, in some cases up to forty you know, nearly half of males are using a claw that misrepresents their ability to fight.

to each other. We're not just waving our claw around in the air and so forth. That's certainly true, though I would say I'm I'm always cautious on the show to draw too many direct analogies from animal behavior to

lessons in human life, because not just any animals. Yeah, but I think it's absolutely true that that our lives are sustained by tons of systems that rely on honest communication, and that when you reach certain thresholds of lying within those systems, the systems do break down, and that can have devastating consequences. Like our lives are sustained by webs of trust, and you know, enough violations of that trust pile up, and like there are devastating consequences for the species.

We briefly mention the late Japanese pro wrestler of Grand Naniwa and the two thousand and six comedy crab Goalkeeper, but there are of course numerous other monster crabs and kaiju crabs to reference. There's one in the nineteen seventy Toho film Space Amiba, and then there is of course Ibira Horror of the Deep from the nineteen sixty six Godzilla movie of the same name. I think the US name for this is what Godzilla versus the crab monster.

flying pirate ship sort of. There's a giant robot, and then there is also a giant crab. And I included images of this crab for you here, Joe.

attack one of the human characters. Okay, There of course plenty more recent examples of crab related beings in Japanese pop culture. There is, I believe if I'm pronouncing this correctly, there is crab Lante from One punch Man. This is not a show. I'm really familiar with it all. It's based on Amonga. A twenty sixteen episode featured this crab based human who kind of looks like a muscly man in a pair of tidy whitey underwear, but his torso and head they're all like crab based.

And as general types, these are going to be more embellished in the actual telling, you know.

a crab saving a girl from a snake. This one, this particular trope of a crab protector factors into a key early Japanese animated film, nineteen twenty five's Crab Temple omen and in fact, future big time Japanese director Tamu Ocheedah worked on this one. He's a guy who's really not otherwise known for animation, most famous for such Japanese

films as fifty five's Bloody Spear at Mount Fuji. Sixty two is the Mad Fox and sixty five is the Fugitive from the past, but he was involved in this bit of animation, and the style is that of silhouette animation. Joe quoted screenshot here. I think this will remind you of something.

too much on that sort of thing. You can enjoy it without being able to read Japanese or know the translation of the text. But yeah, you have these great scenes where a woman saves a crab and is later saved from a snake by swarming crabs.

be the story of the Toad and the Crab. Bearing in mind again, this is a tail type summary and it is in translation, so if it feels a little choppy, that's why. Okay, all right, So this is the first story. Toad and Crab were friends. Once Toad does not listen to Crab's advice, and in consequence, Toad is trodden on by a horse, his tongue is pressed out or his eyes stick out. Crab mocks Toad. Toad says that a his tongue is out because he is pretending to eat mochi,

or his eyes stick out because he is staring. So okay, I love what we're beginning to learn here about certainly about Toad, but also about Crab. Crab is not going to suffer foolishness and let it go unrecognized, and Toad is going to lie his face off to save face, even after being stepped on by a horse.

The branch breaks and mochi falls to the ground. Crab carries it into his hole. Crab does not give mochi to Monkey, who in return drops dung into the mouth of crab hole. Wow, I'm to assume this means like, the monkey goes up to the crab hole, positions butt over the crab hole, and begins to defecate. But I think you can all see where this is going. His bottom is pinched by crab. Monkey gets himself released from the pinch in exchange for giving his hair to crab.

For this reason, Monkey's face is red and crab has hair on his legs. Wow.

was reading about this one. This one's not referenced in one of the main yochai books that I often turned to, but it is in Zach Davison's Ultimate Guides Japanese Yokai, and it's also listed on Matthew Meyer's yokai dot com website. It involves crabs and riddles and does seem directly connected to the aforementioned tale type. So the creature here, I'm

going to and spoil what the yokai is. It is a giant crab that takes on the disguise of a wandering priest who apparently asks riddles of people he runs into, or it runs into, and the main story seemingly becomes popular is part of a Caujun comedic play. According to Meyer, and then Davison references an eighteen eighty five written record. It seems to be a recording of a story that was told at some point after seventeen twenty six, given

a reference to a renamed mountain in the work. So in the version that Meyer relates and Davison also essentially relates the same story, so I think they're in agreeance for the most part. Here you have a wandering priest and he arrives at a temple that seems cursed to lose a new head priest anytime one is assigned to it. So there's a rural temple every time I'm a new priest is sent out there to take care of it. They disappear after a single night, and the local villagers

just assume the place is haunted. There's some sort of vengeful ghost here killing every priest that shows up. The wandering priest that has arrived in our story, however, doesn't know anything about this. He's going door to door in the village looking for a place to sleep, and the villagers are like, hey, why don't you go check out that ruined temple? Wow? Cold, Yeah, I mean I don't know how we're supposed to I was supposed to take that,

but yeah, He's like, okay, sounds good to me. He goes there, goes inside, falls asleep, and then when he wakes up, there's a priest standing or squatting beside him, kind of hovering over him, and this stranger priest asks him that very crab riddle, what has eight small legs two large legs, walk sideways and his eyes pointing straight

upwards towards heaven. And the wandering priest not only solves the riddle, but in solving it, sees through the disguise and he declared he either says you were a crab or says the answer is crab, that's what you are, something to that effect, and then he picks up his priest's staff. He strikes the crab and this causes the disguise to fall away from the monster crab the crab since the gig is up, the monster crab scuttles sideways

out of the way. The priest throws his staff at the monster and it cracks the creature's shell, but the crab still escapes. The villagers show up shortly after this, and they're like, hey, what's going on. We heard some ruckus. We can see you're not dead. That's good, And the priest says, all right, everybody, we're going to drain the

pond behind the temple. They do so, and they uncovered the numerous skeletons of all the dead priests that had been assigned to the ruined temple over the years, the ones that had never survived a single night. And they also find the body of a giant dead crab with a cracked shell.

creepiness to it. It made me wonder if, presumably it has been reproduced on the stage in some of these comedic plays, but it seems like this one would be a great one for adaptation into animation or even live action.

Maya refers to. Davison also mentions that the travel guide Hiram may Show junra Zua from eighteen oh four has grant giant crabs in it the torment people, and he also writes quote the great monk Kobo Dashi banished the crab and the slope where it lived is called Kanakazaka, a crab slope to this day. So there are some other tales out there floating around of monks holy men engaging in battles against the crab.

species on this is is drippy Senika. I included some images of this particular crab for you, Joe, and yeah, I mean looks like a demon face. This is a very very similar situation to the samurai crabs that we were discussing earlier.

What would he do? And you know, it can be endlessly amusing in the picture, but it's not necessarily not necessarily much to talk about regarding it.

would love to hear from everyone out there. Just a reminder first of all, yes, Stuff to Blow Your Mind has been around as a podcast for quite a while, and if you would like to dig into the audio archives of the show, you can find us wherever you get your audio podcasts. It goes back years and years. Let's see. We'll remind you that we're primarily a science and culture podcast, with core episodes on Tuesdays and Thursday,

short form episodes on Wednesdays and on Fridays. We set aside most serious concerns to just talk about a weird film on Weird House Cinema. Those sometimes those selections do factor in to our discussions on core episodes.