AMIT KATWALA
Researchers have created jellyfish whose nerve cells light up when they fire, offering a tantalizing view of neurology before the rise of the brain.
WE OWE MUCH of our understanding of how memory works in the brain to an unassuming sea slug called Aplysia californicus. Itâs about a foot long, reddish brown, and has been favored by scientists since the 1960s because its neurons are big enough to jam an electrode into.
That wasnât the only time researchers have plumbed the ocean depths looking for answers about our own neurology: Giant squid taught us the fundamentals of action potentials, the means by which signals propagate along nerve cells. The horseshoe crab helped to shed light on how our visual system works (despite the fact it has eight more eyes than we do). The octopus offers insights into the evolution of sleep.
âThereâs this long, beautiful history of people going and finding marine invertebrates for whatever the questions were at the time,â says Brady Weissbourd, a postdoctoral scholar in biology and biological engineering at Caltech. Weissbourd is the lead author on a recent paper in Cell that brings another creature into the foldâa jellyfish thatâs been genetically modified so that its neurons glow when they fire. It could give us new insight into the workings of minds quite unlike our own.
The jellyfish, specifically a species found in the Mediterranean called Clytia hemisphaerica, was the perfect candidate for scientific research. Itâs about a centimeter wide when fully grownâsmall enough to fit on a microscope slideâand, like many jellyfish, itâs transparent. The researchers built on that potential by introducing a snippet of DNA called GCaMP, which creates a green fluorescent protein. GCaMP has been widely used in research on mice, zebrafish, and flies, but it actually originally comes from a jellyfish thatâs closely related to Clytia, so Weissbourdâs team also had to knock out the genes for four other green fluorescent proteins that naturally occurred inside them.
To insert the glowing genes, they took advantage of Clytiaâs unique life cycle. Its reproductive system is triggered by light. âExactly two hours after the lights go on, the jellyfish release eggs and sperm into the water,â Weissbourd says. The researchers switched on the lights, collected the eggs, and injected them with the snippet of code for the green fluorescent trait that they wanted to insert, along with a protein that helped to splice it into the jellyfishâs DNA.
A Gene-Tweaked Jellyfish Offers a Glimpse of Other Minds | WIRED