How was Akatsuki members able to replace their bodies?

Question

In Naruto Shippuuden Episode 16,I came across the scene where Akatsuki members were controlled with in another bodies.What kind of jutsu is that?

Answer 1

I assume you are looking for this.
It is called as the Shapeshifting technique used by pain.
According to the Wiki:-

This technique allows Pain to allocate a portion of an individual's chakra and transfers it into a living human sacrifice, allowing the original to fight via an elaborate "copy". The appearance of the person on whom the Shapeshifting Technique is performed is completely identical to the original person. The technique will imitate any weapons, tools or kekkei genkai held by the original person, allowing the copy to fight with them. The power of the copy is in proportion to the volume of allocated chakra, which is decided by Pain.

If you want some more info then you can check Kazekage Rescue Arc on this page and some more about the jutsu.