Skeleton Shrimp, Feather Duster Worm, and 18-scaled worm

There are two skeleton shrimp on top of the piece of kelp in the center of the container in this video. The one to the left is carrying many, many juvenile skeleton shrimp on its body while the one above seems to check on the other. Perhaps a pair? Or a curious neighbor? There is something curiously cute about these skeleton shrimp and their mannerism.

To the left you can see a feather duster worm and maybe a nereid worm?
 

 This is an 18-scale worm upside down, followed by a video of it right side up revealing its scales. It's "feet" are broom-like. It must be used for filtering or some other purpose.

 

 This is the feather duster worm's radioles? radioli?