Another line of descendants from the same ancestor gave rise to somewhat different opsins and ion channels in insect and mollusc eyes.

The monster’s haunt was the marshes of Lerna, near rgos, from which he periodically emerged to harry the people and livestock of Lerna. Plachetzki’s team then built a family tree of opsin gene sequences from 22 highly diverse creatures, and found that opsins in hydras and humans evolved from those in a common ancestor. Hydra, also called the Lernean Hydra, in Greek legend, the offspring of Typhon and Echidna (according to the early Greek poet Hesiod’s Theogony), a gigantic water-snake-like monster with nine heads (the number varies), one of which was immortal. “This is conclusive evidence that these animals, the Cnidaria, have light sensitivity based on this kind of opsin and transduction, just as we do,” says Dan Nilsson of the University of Lund in Sweden, who has also investigated hydras’ light reception. Moreover, they found that a drug that blocks those channels stopped hydras responding to light, showing they are used for phototransduction. Plachetzki’s team found that they make them together in nerve cells. Hydras have the same types of opsins and ion channels as we do. In the animal kingdom, organisms from different clades exhibit varied regeneration abilities. However, the namesake real-life animal the Hydra magnipapillata, or simply freshwater. Most of us would know about the Greek mythical beast Hydra, the serpentine water monster that could supposedly regenerate two heads in case one of its original ones were chopped off. This causes another type of protein, an ion channel, to generate an electrical signal along nerves connecting the eye to the brain – a process called phototransduction. Regeneration of lost body parts is essential to regain the fitness of the organism for successful living. The ‘immortal’ Hydra: An animal that can seemingly live forever. Rod and cone cells in the human retina contain proteins called opsins that change shape when light strikes them. “But if you look at its components you can start to piece together how it happened.” That’s especially feasible now that genes from the earliest animals, such as the hydra, are being sequenced. Hydra: noun a many-headed serpent or monster in Greek mythology that was slain by Hercules and each head of which when cut off was replaced by two others. “If you look at something as complex as an eye, you might be at a loss to explain how the whole structure evolved at once,” says Plachetzki, now at the University of California, Davis. review on toxicity assessment of persistent emerging pollutants (EPs) and associated microplastics (MPs) in the environment using the Hydra animal model. David Plachetzki and colleagues at the University of California, Santa Barbara, have found that hydras “see” light using two proteins closely related to those in our own eyes. The tiny freshwater hydra has no eyes but it will contract into a ball when exposed to sudden bright light. Fresh evidence to the contrary has now arrived, courtesy of a creature related to jellyfish.

One of creationists’ favourite claims is that an organ as intricate as the eye could never have simply evolved.