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An eyeless sea creature , connect to jellyfish and sea anemones , may nonetheless be capable to " see " light and dark , say researcher who found light - sensitive neurons that work in a manner similar to human visual sense .
" I would n’t call this visual sense , because as far as we have intercourse the hydra are not processing info beyond what ’s luminousness and what ’s dark , and vision is much more complicated than that , " said subject researcher Todd Oakley of the University of California , Santa Barbara .
The freshwater polyp,Hydra magnipapillatahas light-sensitive neurons that trigger the firing of the organism’s barbed stinging cells called cnidocytes, researchers have found.
These tinyfreshwater polyps called hydraare part of the Cnidaria family , and likejellyfishand other family members sport stick cell call cnidocytes to help oneself them catch prey . Specifically , the hydra studied ( Hydra magnipapillata ) has a elementary mouth surrounded by tentacle containing barbed cnidocytes , which they apply to daze animate being like the H2O flea , before eat them alive . Next to the stinging cell are sensorial neurons .
" Hydra prick cellphone were already roll in the hay to be touch - sensitive and taste - sensitive , but no one had ever cogitate before to look for clear sensitivity — probably becausethey do n’t have eyes , " Oakley sound out in a program line .
Hydra are simple - looking creatures , under a half - inch ( 1 centimetre ) long and transparent , though this can change depending on the color of the solid food they have just eaten . They are also somewhat athletic , rank their tentacle on the substratum , before release and performing a somersault .
The opsin in the tentacles ofHydra magnipapillatais shown in blue, while the cnidocytes and neurons are shown in red.
" There is a sure elegance to their movement , " David Plachetzki , a postdoctoral fellow at UC Davis , told LiveScience in an interview . " They look like they were design with an art - deco count to them . "
In their report , Oakley , Plachetzki , who at the time was at UCSB , and their colleagues found factor for a light - sensitive protein called opsin inside thesesensory neuron , and what ’s more , they discovered the protein regulates the firing of the polyp ’s harpoonlike cnidocytes . The whole summons is directed by light ; the stinging cnidocytes appear to kindle less often in bright light versus dimmed light . [ 8 Bizarre Creatures on Earth ]
They also found these sensory neurons check the ion epithelial duct and extra protein required to convert light into electric signals , the same operation that go on in the human being retina and allows us to see .
The research worker are n’t certain why light is the trigger , though they speculate it could have to do with fair game , as twilight mark the time when most of their quarry comes out to forage .
" Another reason is that there could be a modest shadow tramp on the tentacles by the quarry , " Plachetzki observe , suggesting the dim luminance would set off the cnidocytes to flack .
The light cue may also help with their death - over - end somersaulting locomotion , as it could signal that the tentacles are facing the substratum ( aside from the surface lighting ) to which they need to attach , he tally .
