Add a solid layer
Add Red Giant 3D stroke to it
Make a path with Bézier curves in it on the same layer.
Adjust the taper settings in 3D stroke to look like the original tentacle
Select your Mask Path ...
As far as I know, there isn't a great automatic way of doing this in AE.
One technique is to make keyframes on your all shape paths, then paste the initial shapes into the path of the end shape after ...