The orange elephant ear sponge, or the Agelas clathrodes, does not have a complex immune system. Sponges do not have the complex immune system of most other animals. However they reject grafts from other species but accept them from other members of their own species. In a few marine species, gray cells play the leading role in rejection of foreign material. They are the "protectors". A graft is accepting a piece of body tissue from another organism as your own. When invaded, they produce a chemical that stops movement of other cells in the affected area, therefore, preventing the intruder from using the sponge's internal transport systems. If the intrusion persists, the grey cells concentrate in the area and release toxins that kill all cells in the area. The "immune" system can stay in this activated state for up to three weeks.