The galaxy's "tentacles" are long tendrils of star formation that trail behind the galaxy's disk, resembling the aquatic animal. These tendrils are formed by the interaction between the galaxy and the intra-cluster medium, which is a superheated plasma that pervades galaxy clusters. As a galaxy moves through a cluster, they ram into that intra-cluster medium, which strips gas away from the galaxy and draws it out into long trails of star formation.
