Acaratarii

The Acaratarii are a race of parasitic, slug-like creatures created by Adam as supersoldiers. The Acaratarii infect hosts by entering their bodies through their mouths, burrowing into the spine and gradually melting into it. A common trait of immediate infection by an Acaratarii is blood trickling from the corners of the mouth, bruising on the throat, and spasms. Over time, Acaratarii hosts gain massively increased strength, speed and reflexes, the ability to regenerate nearly any wound, an immunity to disease and poison and glowing eyes.

Adam's spy
This Acaratariii took over Samantha Endesha's body on Nimoy and proceeded to kill and devour most of the local populace. On Radiance IV, it left her body due to her serious wounds and posessed a Bytrysk soldier. Later, when that soldier was taken to Atlantis, this Acaratarii jumped into the body of a nurse treating the soldier. Using this form, it alerted Adam that John Shepard was still alive. As a reward for it's loyalty, Adam allowed it to keep it's current body and indulge in a huge feast.