The study revealed an accurate model of the stinging organ of sea anemones

All summer beachgoers are familiar with the painful reality of jellyfish stings. But how do the stinging cells of jellyfish and their coral cousins ​​and sea anemones actually work? New research from the Stowers Institute for Medical Research reveals an accurate operational model of the stinging organelle of the sea anemone, Nematostella vectensis. The study was published online in Nature Communications On June 17, 2022, led by Ahmet Karabulut, a pre-doctoral researcher in the lab of Matt Gibson, Ph.D. Their work involved the application of advanced microscopic imaging techniques along with the development of a biophysical model to enable a comprehensive understanding of the mechanism that has remained elusive for more than a century. The insights gleaned from the work could lead to useful applications in medicine, including the development of microscopic therapeutic delivery devices for humans.

Stowers’ team’s new model of stinging cell function provides important insights into the highly complex structure and release mechanism of nematocysts, the technical name for stinging organelles. Karabulut and Gibson, in collaboration with scientists at the Stowers Institute Technology Centers, used advanced imaging, 3D electron microscopy, and gene-knockdown methods to discover that the kinetic energy required to penetrate and poison a target includes both osmotic pressure and elastic energy stored within the multiple sub-structures of a nematode cyst.

We used fluorescence microscopy, advanced imaging techniques, and 3D electron microscopy along with genetic disorders to understand the structure and mechanism of operation of nematocysts.”

Ahmet Karabulut, pre-doctoral researcher

Using these modern methods, the researchers describe the explosive degassing and biomechanical transformation of nematode cysts during shoot, grouping this process into three distinct stages. The first stage is the initial projectile-like discharge and targeted penetration of a densely coiled suture from the nematocyst capsule. This process is driven by the change in osmotic pressure from the sudden flow of water and the elastic expansion of the capsule. The second stage refers to the unloading and elongation of the thread shaft core structure which is further pushed by the release of elastic energy through a process called inversion-; the mechanism by which the shaft turns inward-out; Forming a triple helical structure to enclose the fragile interior of a tube decorated with thorns containing a mixture of toxins. In the third stage, the tubule then begins its own inversion process to elongate into the soft tissues of the target, releasing neurotoxins along the way.

“Understanding this complex sting mechanism could have potential future applications for humans,” Gibson said. “This may lead to the development of new therapeutic approaches or targeted drug delivery methods as well as the design of microscopic devices.”

The entire stinging process is completed within a few thousandths of a second, making it one of the fastest biological processes that occur in nature. “The first stage of nematocyst release is very rapid and difficult to capture in detail,” Karabulut said.

As is often the case in basic biological research, the initial discovery was merely a curious coincidence. Karabulut incorporated a fluorescent dye into a sea anemone to see what it looked like when its worm-rich tentacles were turned on. After applying a set of solutions to both activate the nematocyst discharge and at the same time maintain its micro-infrastructure in time and space, he was shocked that he had accidentally picked up several nematocysts at different stages of firing.

“Under the microscope, I saw an amazing shot of the discharge filaments on the probes. It was like a fireworks display. I realized that the filamentous cysts had partially emptied their filaments while the reagent I used at the same time fixed the samples immediately,” Karabulut said.

“I was able to take pictures that show the geometrical transitions of the thread during firing in a beautifully orchestrated process,” Karabulut said. “After further examination, we were able to fully understand the geometric transformations of the nematocyst filament during its operation.”

Elucidating the elaborate choreography of nematocyst release in sea anemones has some interesting implications for the design of engineered microscopic devices, and this collaborative effort between the Gibson Laboratory and the Technology Centers at the Stowers Institute may have future applications for drug delivery to humans at the cellular level.


Journal reference:

Karabulut, A.; et al. (2022) The architecture and operating mechanism of the stinging organelle. Nature Communications.