tentacles” are really intestines. As they approach their prey, Sillas literally turn themselves inside out so their stomachs can wrap around their victims. Their powerful gastric juices then work directly on their prey – spaceships or other space-dwelling creatures. Sillas are themselves preyed upon by Asteroid Fish.
To see how this works try blowing a rubber glove inside out and then outside in again. Make sure nobody has been using the glove to clean a drain or unblock a toilet prior to this experiment.