Pteraster tesselatus is noted for its external secretion of massive amounts of mucus. The mucus repels most animals, and fouls their respiratory physiology, if contact is maintained for any length of time. It provides protection essentially 100% of the time from Solaster dawsoni and Pycnopodia helianthoides, the only local stars that attempt to feed on Pteraster. The mucus, which is a simple mucopolysaccride, is produced in three different types of unicellular glands located in the epidermal tissues along the supradorsal membrane. Pores along the lateral walls of the ambulacral grooves provide fresh sea water for the dermal branchiae contained in the nidamental cavity located between the supradorsal membrane and the body wall. P. tesselatus has a very strong chemoreceptive ability to locate prey. It prefers sponges, but feeds on a great variety of sessile organisms, as well as detritus. It also feeds on Chlamys hastata and C. rubida, which have their valves epizoically overgrown with either Myxilla incrustans or Mycalft adhaerens.