The Periphyllopsis galatheae is also known as, the crown jellyfish. The crown jellyfish is a carnivorous jellyfish. They paralyze their prey with their stinging cells called cnidoblasts. For feeding, they hold their tentacles up alongside their bell, swim downward about 10m, and then drift upward. At that moment, the tentacles quickly move to their mouth, coil, and then enter the stomach. The Crown jellyfish undergoes straight up and down movement from deep water in the daytime to shallow water at night in order to follow, or catch their prey. They go to lagoons and estuaries to feed. The diet of the Crown Jellyfish is plankton up to 1/5 inch in diameter, including diatoms, algae, invertebrate eggs, mollusk larvae and so on. Their main Predator is a turtle.

The crown jellyfishes color is Transparent which means no color but still reveals the reddish brown stomach and pinkish insides. The crown jellyfish has a Swimming bell and 16 deep notched lappets, in addition, the tentacles appear from the bell surface, and they repeat a pattern of three tentacles and one rhopalium (a sensory structure that lies in an indentation in the edge of the jellyfish’s bell. Jellyfish also have dissimilar ways of swimming, for example, crown jellyfish swim by rhythmic pulsations of the umbrella (bell). Swimming is controlled by a simple nervous system and by sense organs.

These jellyfish have a different shape because of a deep groove running around the bottom of the umbrella, giving them the appearance of a crown which is where crown jellyfish became its name. They are delicate soft-bodied animals. Crown Jellyfish have a cone-shaped body. They are around 20cm tall and 17cm in diameter. From the ocean, they are usually less than 5cm in size.

They live in the mesopelagic depths (between 200m and 1000m, called the twilight zone) in all oceans worldwide, but mostly in the Pacific Ocean and the Atlantic Ocean. It is about 7 degrees Celsius (45o F) in the water. This temperature is really cold. The crown jellyfish is in the classification of Animalia (Kingdom), Cnidaria (Phylum), Scyphozoa (class), Coronatae (order), Periphyllidae (family), Periphyllopsis (genus), and Periphyllopsis-galatheae (species).

The crown jellyfish swims downward when it is exposed to a bright light (such as the sun). Fertilized eggs are released in deep water, where they drift, not feeding for several months. Their bodies are 95-99 percent water based jelly, so that the whole body contains less than 5 percent organic matter. They are invertebrates which are animals with no bones, exoskeleton, or shell to protect or support them.