It turns out sharks, skates and rays are home to the most powerful proton conductors found in the natural world: it’s all in the head.
A new discovery in the US has revealed that some jelly in sharks’ heads can conduct protons at a level completely unexpected, comparable (though still well short) of state-of-the-art proton conductors like Nafion.
Researchers from the University of Washington investigated why it was that certain sea life can detect particularly weak electric fields – knowing that a collection of strange organs played a part.
However, they discovered that the jelly – which fills canals that link electrosensory cells to ‘the ampullae of Lorenzini’ – conducts protons at a level 40-times lower than Nafion.
This sounds like a limited level, however, Marco Rolandi, author of the paper, called it a “very exciting development”.
(A and B) Skates and sharks locate their prey by detecting the weak electric fields naturally generated by biomechanical activity. (C) A network of electrosensory organs called the AoL is responsible for this sense. (D) An individual ampulla consists of a surface pore connected to a set of electrosensory cells by a long jelly-filled canal. Sharks and skate can sense fields as small as 5 nV/cm despite canals traveling through up to 25 cm of noisy biological tissue. (E) A sample of the AoL jelly on an electrical device is presented. Scale bar, 0.5 mm.
Hoping it leads to further investigation into the electrosensing function in sharks, skates and ray, Rolandi called the species’ capabilities “rather exceptional”. A collection of interconnected ampullae allows sharks, skates and rays to detect changes in the electric field as small as 5 nanovolts per centimetre.
Rolandi and his colleagues suggest sulfated polyglycans in the jelly (keratin sulfate) may contribute to its high proton conductivity, which generally occurs when ordered hydrogen bonds occur. Developing this research further could improve sensor technology.
“The first time I measured the proton conductivity of the jelly, I was really surprised,” said Erik Josberger, who worked on the research. “I didn’t expect a natural material to approach the proton conductivity of an engineered material like Nafion.”
Shark image via Shutterstock
