though sea urchins don’t have eyes, they are covered in photoreceptors which collectively act as a retina, effectively making their entire bodies one big compound eye. sea urchins, one of the few marine organisms to have their genome sequenced, have about 23,000 genes (like a human), several of which are associated with sight, including those that govern the development of animal eyes.
"comparing all the genes of the sea urchin, it’s actually quite similar to humans," said george weinstock, who led the sequencing project. they are one of the few invertebrates on the human branch of the evolutionary tree. yet interestingly, they seem to be the only example of a deuterostome to have the rhabdomeric light sensors associated with protostomes, suggesting that rhabdomeric light detectors have been the norm for eyes throughout much of the animal kingdom’s history.
"we think of animals that have a head with centralized nervous systems and all their sense organs on top as being the ones capable of sophisticated behavior, but we’re finding more and more some animals can do pretty complex behaviors using a completely different style," notes sönke johnsen, a marine biologist at duke university who conducted the study on sea urchin vision.
the way that urchins apparently carry out eyesight - with a diffuse nerve net, where no region looks like a central processing unit - reflects how scientists are now often designing robots. “they’re finding it might be a lot better with a distributed system with many little processors and simpler sensors and simple rules, which end up creating fairly complicated behaviors as emergent properties.” [see: starlings post]”
photos of sea urchin tests up close by paul richman. when alive, tube feet would be seen coming from the holes, which the sea urchin uses primarily for sight, with the smaller dents seen in the tests, also containing photoreceptors, used for shading and blocking light. text sources.
What is the point of a gate that does not lead anywhere? asked Nameless, turning to avoid the glare of the setting sun.
The Scientist squinted ahead as the semicircular disk continued its downward trajectory past the horizon, and finally replied. To frame that which we otherwise might not notice.
Thank you so much to everyone who bought Nameless & the Scientist Book 1! I’m so stoked by your support. The book is currently being printed (!!) and I’ll start mailing them out on the 27th May! (when the shipment arrives)
Fukubukuro Dessert in Tokyo, Japan, serves unusual flavoured ice cream in sets of 6 taster-scoops. I got: Tulip, Crab, Garlic (Dracula), Coal, Eel and Wasabi flavours. I was given a sachet of herbs to put on the eel one. The flavours were all spot on (I don’t know what I expected). I’m pretty sure the crab one had actual bits of crab in it. Other flavours on their menu: Potato, Shark fin, Miso noodle, Indian curry, Beef tongue, White Shrimp, Double Cheese, Corn, Rose, Eggplant, Pumpkin, Basil and Oyster.