We owe a lot To our understanding of how memory works in the brain to a humble marine slug called Aplysia californicus. About a foot long, reddish-brown in color, it has been preferred by scientists since the 1960s because its neurons are large enough to jam an electrode.
It wasn’t the only time researchers have probed the depths of the ocean for answers about our neuroscience: giant squid taught us the basics of action potentials, the means by which signals propagate along neurons, and the horseshoe crab has helped shed light on how it works. Our visual system (despite the fact that it has eight more eyes than we do). Octopus offers insight into the evolution of sleep.
“There’s this long and beautiful history of people going and finding marine invertebrates whatever the questions were at the time,” says Brady Weisbord, a postdoctoral researcher in biology and biological engineering at Caltech. Weissbourd is the lead author of a recent research paper in cell Which brings another creature into the fold – jellyfish that have been genetically modified so that neurons glow when released. It can give us new insights into the way minds function quite unlike our own.
Jellyfish, a species found specifically in the Mediterranean, is called Clytia hemisphaericaHe was the ideal candidate for scientific research. They are about a centimeter wide when complete — small enough to fit a microscopic slide — and like many jellyfish, they are translucent. The researchers built on this potential by introducing a DNA extract called GCaMP, which produces a green fluorescent protein. GCaMP has been used extensively in research on mice, zebrafish, and flies, but it actually comes originally from the closely related jellyfish. Cleia, so Weissbourd’s team also had to knock out the genes for four other GFPs that naturally occurred within them.
To insert the glowing genes, they took advantage of that CleiaUnique life cycle. His reproductive system is powered by light. “Exactly two hours after the lights are on, the jellyfish releases eggs and sperm into the water,” Weissbord says. The researchers turned on the lights, collected the eggs, and injected them with an extract of the code for the green fluorescent trait they wanted to insert, along with a protein that helped them paste into the jellyfish’s DNA.
Fertilized eggs develop into larvae, which swim around in search of a hard surface to attach to—in nature, this might be a rock that, in the lab, a microscopic slide provided a useful alternative. From there, they grow a small tumor that develops into a colony. These colonies are essentially immortal, and release tiny medusa – which over a few weeks grow into the shower cap-like gelatinous organisms we call jellyfish. “It’s more like a flower or something,” Weisspur says. “Their job is to go out and spread the seeds.”
Now, researchers have a creature they can watch under a microscope as it eats (a diet of brine shrimp) and flexes its body, while the neurons that govern these behaviors glow. “You can really do high-resolution experiments, looking at the activity of each neuron over time while the animal is behaving,” Weissboard says. They can basically read his thoughts – a mind completely different from anything we know.