Scientists identify first brainless creature that sleeps
A Caltech team led by Indian-origin researcher Ravi Nath has demonstrated primitive jellyfish called Cassiopea, sleep despite lacking a central nervous system. Dubbed "upside-down jellyfish" as they lie inverted on seafloor, the animals displayed periods of inactivity at night, pulsing 30% less often than during daytime. The researchers, however, did not examine whether jellyfish "dream". 