Like most members of Phylum Cnidaria
, the tentacles of Phillorhiza are equipped with stinging cells called cnidocytes. Within these cells are stinging organelles called nematocysts. When discharged, nematocysts can immobilize small prey items that are subsequently ingested. Nematocysts are also used as a defense mechanism. The planktonic egg and larval stages of several fish species (including commercially important species such as red snapper in the gulf of Mexico) are probably important as prey items.Additionally, throughout its native range and much of its introduced range, P. punctata
also harbor endosymbiotic zooxanthellae within their bell. In a relationship analogous to that of reef-building tropical corals and their resident zooxanthellae, primary production of the photosynthetic zooxanthellae likely fulfills a large proportion of the nutritional needs of the host jellyfish (Garcia and Durbin 2003).The invasive Gulf of Mexico P. punctata
populations were/are unusual in that they lacked endosymbiotic zooxanthellae (Graham et al. 2003). Zooplanktivory was/is the sole trophic mode of these populations which, nonetheless, attained high population numbers.