Jellyfish
Most jellyfish do not have specialized systems for osmoregulation, respiration and circulation, and do not have a central nervous system. Nematocysts, which deliver the sting, are located mostly on the tentacles; true jellyfish also have them around the mouth and stomach. Jellyfish do not need a respiratory system because sufficient oxygen diffuses through the epidermis. They have limited control over their movement, but can navigate with the pulsations of the bell-like body; some species are active swimmers most of the time, while others largely drift.
The rhopalia contain rudimentary sense organs which are able to detect light, water-borne vibrations, odour and orientation. A loose network of nerves called a "nerve net" is located in the epidermis. Although traditionally thought not to have a central nervous system, nerve net concentration and ganglion-like structures could be considered to constitute one in most species. A jellyfish detects stimuli, and transmits impulses both throughout the nerve net and around a circular nerve ring, to other nerve cells. The rhopalial ganglia contain pacemaker neurones which control swimming rate and direction.
Jellyfish as food
Jellyfish salad, a popular dish in some areas of Asia, may be prepared using cold marinated jellyfish that is thinly sliced. Some Asian airlines serve jellyfish salad as a part of their airline meal fare. Jellyfish sushi is consumed in Japan. In Thailand, a crunchy style of noodle is produced using jellyfish. The Japanese company Tango Jersey Dairy produces a vanilla and jellyfish ice cream. The ice cream is prepared using Nomura's jellyfish ("Echizen kurage" in Japanese), and involves soaking cubes of the diced jellyfish in milk. It has been described as "slightly chewy." Another reaction to the 2009 Japanese Nomura's jellyfish bloom, students in Obama, Fukui designed a Nomura Jellyfish powder to be used to make caramel sweets as part of a NASA-designed food safety management system established in the school.