Left, a hydra stained in blue where the light-sensitive opsin gene is expressed. Right, two tentacle bulbs showing the arrangement of neurons and stinging cells (red), muscle fibers (green) and cell ...

An unusually elastic protein has been discovered in one of the most ancient groups of animals, the over 600-million-year-old cnidarians. The protein is a part of the "weapons system" that the ...

In the absence of eyes, the fresh water polyp, Hydra magnipapillata, nevertheless reacts to light. They are diurnal, hunting during the day, and are known to move, looping end over end, or contract, ...