Starfish bodies aren’t bodies at all, study finds | Hacker News Reader

Starfish bodies aren’t bodies at all, study finds

cnn.com

155 pointsraybb81 comments

Link to the study: https://www.nature.com/articles/s41586-023-06669-2

Starfish are bizarre. They start as a bilaterally symmetrical larva, then grow a stalk that attaches to the sea bed. They grow, then rearrange themselves into a pentaradially symmetrical form.

https://en.wikipedia.org/wiki/Starfish

Plus they can regenerate from a severed limb! Creepy, but very interesting too.

Jellyfish are really weird too. They produce like spores that then go down to the surface and create factories that create little baby jellyfish.

What do you mean by "down to the surface"?

I mean the sea floor haha

Why do you have to be so affable about it ;)?

if they can regenerate from a severed limb does this mean they can be cloned into 5?

My understanding is that they can regrow from all the severed parts if done correctly, so 6 at a time. Arms and central core.

How would a separated arm part nourish itself?

In the Wikipedia article, it states they live off stored nutrients until they can grow a mouth and stomach. So very, very weird!

It depends on the species at least https://en.m.wikipedia.org/wiki/Starfish_regeneration#Degree...

An even more bizarre animal is Dendrogaster, a starfish parasite. Believe it or not, but it's a crustacean.

It grows inside a starfish's body cavity until filling it completely, which explains the strange shape of the parasite.

https://www.australiangeographic.com.au/blogs/creatura-blog/...

Oh, geez, that reminds me of the Mimics from All You Need Is Kill (the basis of Edge of Tomorrow. In the novel, the Mimics are not the alien invaders themselves, but rather nanomachine colonies sent by the actual aliens that infest and control the bodies of starfish, adapting them to combat use.

If you are interested in parasitic crustaceans,you could have a fun time reading about sacculina and the mysterious Y larva

It is really creepy because they often regenerate funny. See reddit https://www.reddit.com/r/deformedstarfish

> Plus they can regenerate from a severed limb!

I think you mean part of head.

So starfishes are like guild navigators from Dune, that took so much mélange spice until they were reduced to giant brains with limbs, but in real life. Amazing!

I had to think of that The Thing scene; yours is much less disturbing.

It turns out they are four dimensional being just poking their heads into our universe to look around.

No wonder Patrick from Spongebob is always so enlightening.

Five dimensional, I would hope

Trying to say they have heads at all seems like trying to cram a square peg into a round hole. It's interesting that their bodies evolved from what was once the head of their ancestors, but in what meaningful sense is it presently a head? It's more like "head" is a discrete label created by and for the convenience of humans, and being a discrete label it doesn't really map cleanly to real world data in all cases.

It's like saying humans have four legs, or dogs have two arms, because the front/top two limbs are related to each other. The labels of 'legs' and 'arms' aren't really meant to be used in this way, regardless of what evolutionary history says.

I agreed with you until I read the article. It actually makes some really interesting observations about the comparison it's making regarding the typical definition of "head" and how body parts in general relate to gene expression patterns. The images in the article are really cool.

The article convinced me that starfish bodies developed from heads, just as I'm convinced that primate arms developed from legs, but it didn't convince me that it's appropriate to call the modern forms of these things heads or legs.

If your education includes substantial aspects of evolutionary developmental biology and genetics, then you have important mental models with which you can work with an organism. If you discover that the whole organism is effectively developmentally a head, then it is extremely appropriate to refer to it essentially as a head.

If you instead relate to the organism in its present form in some more mundane ways then it might not seem that way.

Analogies are failing me, but perhaps it would be like realizing an entire government basically spawned out of the centering concept of religious freedom. The structure of it then makes a lot more sense.

I'd say that whale flippers are homologous to legs/feet, but aren't legs/feet. This article says that starfish are homologous to heads, but I'm not sure whether I'd consider their bodies to be heads or not.

This discovery is to our understanding of starfish what Georges Cuvier’s discoveries of vertebrate morphology were to your present understanding of whales.

Words only have meanings in context. It might now be that in the context of developmental biology, starfish have heads. It is surely the case that in the context of millinery, they do not. But no particular context is canonical, and so you cannot say that in an absolute, context-independent sense starfish do or do not have heads.

For legs and their homologues we have the word "limb" (or should I say fins and their homologues? After all, cladistically we're all fish!) but there hasn't been a need for a term for "head and its homologues". At least not until now, I guess.

The pointwise measurable signatures of genes expressing for head vs trunk kind of deflate that perspective a tad.

Arm yourselves! The head of the language police has arrived To butt his nose into your thoughts To tell you what is meant to be or not. This mouthy busybody rarely rhymes and always prefers others mime. Metaphors, just confusing bores. Similes, not much more. If Orwell had a Frankenstein, he might to us remind: “An elbow is L-bowed only some of the times!”

Would it really be correct to refer to this person as the “head” of the language police?

Only if he is in charge of thought crimes.

You are exactly right and wrong. I teach biology at OSU and tease my students by asking, "Do humans have gills?" Do we? What would you answer?

Then, "Do humans have tails?" Do YOU have a tail?

The answer to both, in biology and evolutionary, YES, we have both. In the case of echinoderms what they have now "used to be" a head, so they are a head.

> The answer to both, in biology and evolutionary, YES, we have both.

But only in those limited contexts is it true, and even then there are caveats. For instance biology textbooks will tell you that great apes are tailless primates. And in virtually any practical sense that's true. You can't yank a gorilla or a human by the tail. You can't get your tail caught in door. Your pants don't have a hole for your tail to poke through. If you told a child that gorillas have tails, you would be seriously misleading that child even if in some technical sense it was true. You would have to explain that gorillas only have tails in a very specific technical sort of way.

If you aren't trying to be cheeky and entertain students with counterintuitive claims, then you would say that great apes have coccyxes, e.g. tailbones, which are the remnants of lost tails.

How about this: Are whales fish? In the traditional sense, a fish is an animal that lives in the water, so whales (and starfish) are plainly fish. But anybody who has ever heard from marine biologists will exclaim that whales certainly are not fish, they're marine mammals. People will be very annoyed with you if you ever call a whale a fish, they'll take it as an insult to whales. But all mammals, including whales, are tetrapods and descended from an ancient lobe-finned fish. So in a cladistic sense you can claim that whales are fish. In the same sense, humans are also fish. And why not? As you say, we have gills too!

You are not correct about a lot of what you are saying. Whales are not fish, but birds are dinosaurs, and humans have gills and tails, but your made up version of "whales are fish" might sound superficially similar but its not how any of that works.

You can not "claim whales are fish" but humans do have gills and those are not the same thing, you are just confusing the two examples because they sound the same.

Do you have a citation for the claim that humans have gills? The closest I can find is that human embryos develop pharyngeal arches similar to fish, but these grow into the jaw and hyoid bones rather than gill supports:

https://en.wikipedia.org/wiki/Pharyngeal_arch

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7547273/

I belive they are only saying the beefy center of the starfish body evolved from a head with legs, rather than a body with 5 legs. It doesn't mean we have to label it a 'head', but that language helps people understand.

I think the more amazing insight here (not a new one though) is that "head" and "torso" aren't just human categories, they are at the root of some very old genes that govern body development for a vast number of species. So starfishes are "heads without bodies" in the sense that they use the molecular/genetic mechanism that in other species shapes the creature's head, but use it here for the entire body.

If alternative forms of cognition are your jam, consider giving the Children of Time series a read: https://en.wikipedia.org/wiki/Children_of_Time_(novel)

Note: I would consider this series science fantasy, not science fiction. I had to kind of unfocus my critical perspective to enjoy it, but I really did enjoy it.

off topic question, whats the difference between science fantasy and science fiction?

Science fantasy, something like Star Wars. Magic in a setting that seems technical. Science fiction, only break a few laws of physics, the fewer the hard the science fiction.

Magic - or - something that sounds science-y but probably is not possible. I call this one science fantasy because there are some big science gaps that are not filled in, so that the story can happen. It makes a better story, but it is not so scientific.

With science fiction, the author describes how things work in enough detail that you can definitely tell that it won't.

In science fantasy, the author glosses over the explanations and just shows you the effects.

In fantasy, the author doesn't care about how it violates known science.

(Technically, fantasy is the root of all literature, but these are the marketing categories we have today.)

How do we apply that classification system to things that are definitely possible but beyond current engineering? Like a space station around Jupiter.

I would suppose by the effort the author makes to make the reader feel it could be possible rather than the actual possibility of it (scifi) versus the author not caring to give the reader an impression that it could be possible by any means of explanation (sci-fantasy)

That's cute, but science fiction does not require a physically impossible premise.

I like to think of scifi as stories that are fundamentally about how a new development in science leads to changes in the world. It could be far-future questionably possibly supertech (The Expanse). It could be near-future changes in social science (1984). It could be future regression of current technology (The Windup Girl).

Mmm, not sure those stories match your idea. The only story I can think of that involves a single change in science is Vernor Vinge's Across Realtime (which is very good).

I think an Expanse author once commented that he'd never really thought about how the fusion drive thingies were supposed to work.

I was imprecise, I didn't mean to suggest that any book should be based on only a single technological change.

> How does the Epstein drive work?

> It works very well, thank you very much.

It's really nice in Across Realtime.

I'm not really a big believer in the 'science' part of 'hard science fiction' - for me, you can basically divide sci-fi into two traditions. The first is based on the old sci-fi magazines that published short stories. Short stories, being characterized by the exploration of a remarkable idea, therefore produces sci-fi that's basically about examining some imagined change, usually scientific, but it could also be social (The Dispossessed, etc). The second is based on old sci-fi comics, serials and pulp novels - and is about characters. It doesn't matter how lightsabers work because Star Wars is entirely about characters. So for me, the Expanse would be in the tradition of Star Wars, while something like Yoon Ha Lee's stuff would be in the magazine tradition, even though it's basically magic with spaceships.

What you are describing is the scifi I like, but not true for a large part of what commonly gets categorized as such.

Now that the furor is over, I'll tell you the secret:

SF, fantasy and all the rest are marketing categories, and so they cannot be depended on in the slightest.

Amazon’s “Homecoming” show is one of my favorite low key science fiction shows. It shows immediate effects of a tiny possible discovery.

No CGI, no special effects - just Good writing, good acting, and good camera work

Thank you.

I'm more confused about it then before.

Logically I get Star Wars/Dune is science fantasy but wouldn't that make Star Trek also science fantasy as wrap drive is never explained (and when it is its not rooted in reality) and how teleport-er is using magic to reassemble atoms at another location? I get it that Expanse and Three Bodied Problem are SciFi but how can the the two categories be quantified in to words?

This is way off topic and i'll stop here. thank you for sending me down a rabbit hole.

I find that science fiction fans are a little concerned with "proper categorization", and often discussions get into people's own personal interpretations. I don't share the OP's definition of the dilineation between scifi and scifantasy, I'd categorize Children of Time as pretty direct scifi, but I also don't care all that much whether someone else wants to give it a different label. I don't think it's incumbent upon the author to justify the plausibility of every technological feat within our current understanding, but more power to you if you do.

I look at science fiction versus science fantasy the same way I look at hard magic and soft magic in fantasy. Hard magic fantasy novels are much more like science fiction than they are soft magic novels and science fantasy has more in common with soft magic systems than science fiction.

Science Fiction / Hard Magic:

The rules are clear and well established. The fantastical elements become almost like characters in the story and have an impact on society and individuals living within the world. The reader can develop a clear understanding of these rules through the writing, and can creatively participate in problem solving using these rules similar to how the character would. You don't need a plausible sciency explanation for how a teleporter works for it to be science fiction versus science fantasy. You need consistent rules on how they are used that the reader can understand and reason about. But when your science officer can pop open a panel and make it do things it's never done before because the plot needs something to move it forward, you're moving towards science fantasy.

Science Fantasy / Soft Magic:

Magic and technology are just plot devices used to move the story forward and less integral to the world setting. Need your short little friends to get out of a dicey situation? Oh yeah, I just so happen to know a spell to summon giant eagles to give us a ride. We haven't talked about it at all before, and you'd have no reason to know it exists. But let's sprinkle a little deus ex machina on this because I'm trying to tell a story not build a coherent world and magic system. Star Trek and Star Wars are both science fantasy because the rules are never consistent and you're constantly running into exceptions for how things work. You as a reader can never fully understand the setting because there's always something fantastical waiting around the corner which breaks the rules and changes things.

Most fiction exists somewhere along a spectrum with authors like Brandon Sanderson and Andy Weir falling more on the hard magic / science fiction side and George Martin and Ian Banks being more soft magic / science fantasy. Are the fantastic elements there as a mechanism to allow cool shit to happen, or are they actually parts of the world for the characters to interact with and overcome with influences shown across society.

I'll disagree with the parent and use the following definitions:

Science fiction is a genre that explores the social consequences of technological advancement on humanity.

Science fantasy is a genre where futuristic technology just serves as a backdrop.

Star Trek at least somewhat delves into the social implications of technological advancement (although less than many other works of sci-fi).

The reason that people get bogged down into discussions of "hard" and "soft" sci-fi here is because hard sci-fi, being more grounded in reality, might have more predictive power in its social commentary.

As with most systems these categories don't work universally because they're firm definitions for complex works which exist on sliding scales. We may identify tropes from a variety of trends and subgenres within a single work of art. Our categories guide us to the greater conversations and traditions some work may be participating in and are no more prescriptive than classifications of evolutionary speciation or morphology. That does not diminish their usefulness: it allows us the freedom to use them as scaffolding to build our own models for the thing itself being studied and compare those models to other's for consistency and depth of consideration.

The real answer is that the distinction between "science fiction" and "science fantasy" is a matter of personal taste and perspective, and there is no objective definition for either. These rigid genre labels are created for the sake of commerce, and for nerds to argue about.

There are arguments to be made for Star Wars and Star Trek as either science fiction or science fantasy, depending on how you slice them. Both are fantasy in that they primarily focus on drama rather than speculative science (Star Trek may have the superficial trappings of "science" but they're really morality plays that just "tech the tech") and include pseudo-mystical elements (The Force/Jedi vs. the Q, telepathy, many of Star Trek's weird space anomalies might as well be magic,) and both are science fiction in that they take place in a universe with "futuristic" elements like spaceships, computers, robots and aliens. One could even argue that Star Wars is the harder of the two settings, as far as sci-fi goes, simply by virtue of leaving more explanation to the imagination, and having more variety in alien design.

But really it's up to you.

"Any sufficiently advanced technology is indistinguishable from magic" :)

It's a spectrum along fiction, often along how possibly something is given our known knowledge of the world and possibly future extrapolations.

Science fiction can be about something entirely possible today that hasn't been done (and could just focus on the social change or response to it, black mirror sometimes opts for this), but often incorporates at least a few giant leaps to help focus us on the parts the fiction is interested in. For example, faster than light travel to allow us to better explore galactic empires and what it means to not have constrained space for nations again.

Science fantasy is the other end of the spectrum, where explaining how something is accomplished or linking it to our current understanding of science is inconsequential. Star Wars is the popular example of this, where generally the explanation of "the force" is so irrelevant that they don't even bother to give it a name beyond the pseudo-descriptive one used. You could replace it's occurrences in the script with "magic" and our understanding and assumptions about it wouldn't change much. In these stories the "science" in science fiction usually signifies it's in space or has aliens, which people associate with the sciences when it involves people out in it.

I think it’s whether or not it attempts to stay within physics. It can still be very out there, like fusion torch rockets or mind uploading, but there is nothing happening that is physically impossible according to what we know about the universe. A physicist would not have to suspend disbelief (much).

This is also called hard vs soft sci-fi where very soft is fantasy.

Fantasy incorporates elements that go beyond any known physics. Sometimes they are explained in world with invented physics like Star Trek, and sometimes they are alien and not explained like the stuff the protomolecule can do in The Expanse.

If it’s alien it’s playing with “what if we met someone WAY more advanced than us?”

It’s not a binary thing. Some stories are super far out in fantasy like Star Wars while others try to be very scientifically accurate like For All Mankind, Gattaca, or most of the human tech in The Expanse.

Technology vs Mysticism

This is one of my top books. I love reading about the spiders evolution. The third book in the series is a little lackluster though.

Another excellent one is the Blue Peril(1911), absolutely alien.

https://fr.wikipedia.org/wiki/Le_P%C3%A9ril_bleu

Love this book!

100% agreed; if you avoid trying to categorize it, the whole series is (IME) really engaging, thought-provoking and worthwhile.

So Patrick is really an old starfish then. He has a torso!

I get vibes of HP Lovecraft's "At the Mountains of Madness" when it describes the creatures in Antarctica.

Free version of the research paper:

https://www.biorxiv.org/content/10.1101/2023.02.05.527185v1

Doctor who predicted this with the face of boe!! At this point it's evident how starfish will evolve in the future...

"with the face of boe"?

(the series) "Doctor Who" predicted this with (their character) "The Face of Boe"

thanks!

(surprised I missed this ref since I was "Whovian" for much of my childhood)

Evolutionary developmental biology is the coolest dang thing out there.

What can this be called besides "evolutionary decapitation"?

"Evolutionary capitation"?

"Evolutionary decorporation"?

Echinoderms didn't "lose a head", that makes no sense.

Of course they are just an animal with multiple life stages.

Quite the opposite. It is really decorporation or hypercapitation.

Wonder if the same thing applies to sea cucumbers or crinoids.

Obligatory "I'm Sorry, Spongebob!"

https://i.imgur.com/fGB9eDF.jpg

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