twitching swimmers on shrimp

[gab.houghton]

what on earth is this shrimp up to?

https://vimeo.com/178747607

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the swimmer fins are rhythmically twitching, what causes this?

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[jayc]

Don't know.

 

Dancing?

Yoga?

[fishmosy]

Looks like it is swimming to hold itself in position in the current. The fish above is doing the same thing. 

[daveron]

Can't explain what causes this, but I had the same thing happening in my TB tank with multiple shrimp twitching and scratching pleopods with their back legs. It seems to be over now, and did not cause any deaths. 

[Zoidburg]

Females will do this behavior when they are spreading their pheromones to attract a male. They may also do it again once their eggs start hatching.