A new study of scientist Howard Hughes and his team from California Institute of Technology in the US found that jellyfish go into a sleep state, making them the first animals without a brain to do so.
The finding pushed scientist into the link between the origin of sleep and the tree of life before the emergence of a centralized nervous system. Howard Hughes said that it is the first time a sleeping animal found without a brain.
The researchers wanted to find out that whether creatures like sponges and jellyfishes could sleep along with their primitive structures. To obtain the result of this finding, they studied Cassiopea jellyfish which is native to mangrove swamps, mudflats, and other warm, shallow waters. They kept the jellyfish in tanks with artificial seawater in labs.
Cassiopea are little different from typical jellyfish, they are silver dollar-sized, patched with black pigment, and rest upside-down on the sea floor, according to the researchers. They have tentacles above the bell-shaped bodies and mini heads like cauliflower. However, their heartbeats are same like jellyfish, contracting and relaxing in a steady rhythm.
A graduate student at Caltech, Ravi Nath said, “We went in at night and videotaped them with an iPhone.” They found their first clue that Cassiopea is slipping. Researchers counted the pulses of 23 jellies over six consecutive days and night through an image processing program.
According to the researchers, Cassiopea is like plants as they don’t really behave like animals. They don’t have the mouth so they suck food through pores in their tentacles.