Asterinas scared of Harlequin Shrimp!

Discotu

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#1
Ive had asterina stars for as long as ive had this tank and havent bothered me. They arent the coral eating variety so figured they'd be part of the cuc. Recently I wondered why i didn't have as much coralline as I've had in previous tanks and suspected the little buggers. I added a pair of harlequin shrimp to clean them up and bam over night it seems like all the asterinas are running for the hills(or glass). They're literally all over the glass and bunched up towards the water line. I thought this can't be a coincidence and a quick google search shows others experienced the same. So fascinating!
 

mchain275

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#2
Agreed, this is one of the most interesting things to observe in a reef tank. Those little starfish have some incredible instincts to evade predators within moments of the shrimp hitting the water. I wonder if it's a response to the shrimp's odor. It's pretty wild to see the sheer quantity of them when they flee to the water line en masse.
 

Discotu

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#3
Yeah i was shocked to see how many asterinas were actually in my tank. It made scoping them up easy then tossed them in a little "breeder" container.
 

bluemon

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#4
Probably something pheromonal.

im sure the harlequin has some to let potential mates know they are there, and starfish have learned to associate that with death
 

JojosReef

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#5
Probably something pheromonal.

im sure the harlequin has some to let potential mates know they are there, and starfish have learned to associate that with death
Or the dying starfish are releasing "pheromones" alerting the others to a predator.
 
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#7
Its the same phenomena as a person farting in a crowded elevator. If its deadly, people start clamoring towards the exit.
 

Discotu

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#8
Another observation...seems like there's also a group of asterinas that are actually drawn to the shrimp. There's a bunch gathered in front of their cave waiting to be consumed.
 

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