Pom-pom crabs fight over tiny anemones, which they hold like boxing gloves | Hacker News Reader

Pom-pom crabs fight over tiny anemones, which they hold like boxing gloves

washingtonpost.com

155 pointsmhb64 comments

> The pom-pom crab, the scientists speculated, is perhaps the only animal on the planet that controls another species’ growth, feeding and asexual reproduction.

Speaking about controlling another species, this story [1] where a wasp performs brain-surgery on a cockroach also seems pretty interesting.

[1] https://www.wired.com/2014/02/absurd-creature-of-the-week-je...

Extended Phenotype territory.

> the only animal

Besides us, that is.

I designate myself and my other fellows as humans.

You can designate yourself as you wish, it doesn't make you/us less of an animal

What is the proper word for "animals minus humans"?

https://en.wikipedia.org/wiki/Non-human

You wrote the first HN comment that made me sad I only can upvote it once.

Humans are animals, even if they're not particularly good at it.

It's hard to say the worldwide apex predator isn't good at it

Not everything I say is literally true. I realize this may come as a shock to my many fans.

More like apex parasite :(

"worldwide apex predator" == "good at it (being animals)" ?

I believe that that sentence could be written from the point of view of the anemone. The situation is unique in that the species of anemone itself may not exist outside of the "captivity" of this species of crab. I could be wrong, but all farm animals and pets are still related to some species of animal outside of human captivity. The closest analog of which I can think is the avocado plant whose seeds, as far as we know, can only be spread via human intervention.

> the only animal on the planet that do this or that

And here comes the "sexy phrase" attack.

Ehhhm... Sorry, but not. There are lots of species that do this.

Is it possible that the only remaining population of these particular anemones is in the claws of these crabs? That the only mechanism they have left for propagating is precisely the fighting and splitting seen in the tests? That would be wild. Could be checked by seeing if they're all clones. (Wouldn't necessarily be proof but it would be evidence.)

Or it could have gone the other way, and the pom-pom anenomes divergently evolved under pressure the only survivors were the ones that continued to divide well under the crab provided environmental conditions.

I'm pretty sure they are fairly prolific outside of the crabs use.

In the reef keeping world you can actually keep Pom Pom crabs in your aquarium with their anemones. If they lose the anemone for some reason, they often will find another anemone or even some coral to use.

Here's more info on the anemone they use.

https://en.m.wikipedia.org/wiki/Triactis

"The pom-pom crab, the scientists speculated, is perhaps the only animal on the planet that controls another species’ growth, feeding and asexual reproduction."

Except for scientists, of course.

I recall reading something about a species of ants that cultivated aphids for some fluid they secrete.

Yes [1]. And leafcutter ants farm fungus. I think the distinction is the level of involvement of the crabs in the anemones' reproduction.

[1]https://www.sciencedaily.com/releases/2007/10/071009212548.h...

This species sounds more like they are in control of the aphids' reproduction, to the point the aphids have evolved a new organ.

https://www.sciencedaily.com/releases/2012/07/120702134037.h...

And botanists. There's a lot of grafting and taking cuttings going on there.

I've probably just horribly offended a bunch of botanists, haven't I?

Some years ago I had a reef tank. Most people start a reef tank by adding live rock. Those are rocks straight out of the sea.

It's amazing what live rock realy means. Every cm³ is covered with some form of live. Worms, crabs, starfish, anemones, you name it.

We know so little about this world. It's a shame we are busy destoying large areas of the ocean.

Another interesting crustacean is the Mantis Shrimp - it's got a fast and powerful punch that reaches 73 feet per second (50 miles per hour) within 3 milliseconds - https://www.youtube.com/watch?v=DtNAqK_V-lg

Aptly named "MANTIS MURDER SHRIMP" on some youtube videos.

Those eyes are crazy. I'm jealous of all of the animals that have a greater range of color perception than us. If I could trade for any trait, it'd be that.

My understanding is human lens is a filter - removes ultraviolet. Early replacements didn't filter, some old folks could see colors the rest of us don't know about!

Mantis shrimp can see light polarization as well. They have amazing vision range.

Humans can, too, though not very well. Stare at a bright white LCD—you should see orthogonal double-fan shapes, one bluish, one yellowish.

I personally see it more readily from red LED digits on my alarm clock at night. IDK if it's generally better conditions or biological difference.

LEDs don't produce polarized light. You might be seeing the matrix scanning.

Don't know why I said LED. Alarm clocks are almost never LED. It's a backlit LCD.

They can see 6 different types of polarization though.

What do you mean by early replacements?

Cataract surgery replaces the lense with an artificial one.

Ah, thanks. I'm surprised I haven't heard of body modders getting that done so they can see UV, that sounds like a neat superpower akin to people who get magnets embedded in their fingers. Going to research risks now..

I'm going to guess the retina doesn't hold up to UV exposure too well. Seems very likely.

You would be right in the case of UVA light [1]. Though it's interesting that we have photoreceptors for UV light in the first place.

1. https://www.ncbi.nlm.nih.gov/pubmed/21646980

Allegedly, Monet painted with more blue colors after his cataract surgery, though it's not a sure thing: http://www.skepticalartist.com/2013/06/25/claude-monet-and-u...

There are some substances that can put you there (at least in mindset) for some period of time. Noticing the beauty of a color you have seen thousands of times is an interesting thing.

I guess you could have cameras that pick up the extra colours linked to something like a Microsoft hololens and displayed somehow like a shimmer for UV say.

Yes. They are the fear of most aquarists because they are real killers. And larger ones can even break the glass.

The Oatmeal had fun with that critter.

http://theoatmeal.com/comics/mantis_shrimp

As did the True Facts episode about the mantis shrimp

https://www.youtube.com/watch?v=F5FEj9U-CJM

That was a damn funny yet informative video. Is that a series?

Yes it is.

https://www.youtube.com/playlist?list=PLOHbM4GGWADc5bZgvbivv...

Saw one of these on a dive in the Maldives. The colors of it's shell are mind blowing. Glad I didn't try to pick it up.

Better quality and longer video https://www.youtube.com/watch?v=vgWy0uOg54A

Boxer crabs induce asexual reproduction of their associated sea anemones by splitting and intraspecific theft https://peerj.com/articles/2954/

> “but we’ve never found a free-living anemone,”

(Fifteen secons of google later...)

And here you have your free-living anemone of the same species.

http://actiniaria.com/img/triactis_producta_1.jpg

You're welcome

that was the most interesting bit of the article for me, so i went to see what the anemone wikipedia page said and i found

> Triactis producta is found in shallow waters of the tropical Indo-Pacific Ocean, its range extending from the Red Sea and Mozambique to Hawaii and French Polynesia. It is inconspicuous, often growing in crevices and concealed among the branches of stony corals. It often occurs in dense clusters of what are probably cloned individuals.

i really wonder how that quote got into the article - was schnytzer somehow misquoted? was he talking about years ago when the anemones were seen on the crabs but not yet found in the corals? it seems unlikely that he would simply be wrong about scientists not having found out where the anemones lived in the wild.

This was one hell of a David vs Goliath match

But... why?!

No need for questions: God works in mysterious ways.

Sarcasm.

For evolution, the answer tends to be "why not?"

And also very often: those who don't do it can't get to have successful sex.

I think the article touched on this when it said the crabs use the anemones like nets to catch food and ward of larger predators.

Food and/or drugs. When two animal species have an intimately codependent relationship like this it's called symbiosis, and it's a very interesting field. Some ants keep herds of aphids, a tiny insect whose secretions apparently taste like delicious caek.

Am I the only one that read this as porn-porn crabs?

No, but if you're like me it might be time to visit the optician again :)

get your head out of the gutter

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