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#EBSstory Delving into squids’ neural system


A team from the MRC Laboratory of Molecular Biology in Cambridge, in collaboration with the ESRF, is looking into the connections of the neural system of squids.

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As they evolve, predators and their prey develop adaptions and counter-adaptions in response to each other’s actions. This process is known as predator-prey arms race, and it is a major driving force behind the evolution of many traits and behaviors in animals, such as speed, agility, camouflage, and mimicry.

Animal vision is a striking example of how evolution refined a simple light detector to sense shadows into a sophisticated organ that is capable of generating an image and extracting a myriad of features enabling elaborated behaviours. For instance, the study of vision in different animal groups has inspired the design of artificial neural networks and their application in the nowadays very successful field of computer vision.

Even though cephalopods are widely divergent from vertebrates in the tree of life, they evolved camera-like eyes, similar in anatomy, optics and function to the vertebrate eyes. Only cephalopods and a few spiders evolved a camera eye among invertebrates.  With the development of the camera-like eye, cephalopods and vertebrates might have evolved similar neural circuits for extracting useful information from what the eyes see, for example to capture prey or to avoid predators. .

The Cambridge team aims to identify and analyse the visual circuits of a cephalopod using X-ray nanotomography at ID16A. Cephalopods have the most complex nervous system of studied invertebrates and exhibit a myriad of elaborate behaviours, driven by their particularly advanced visual system.

“A synaptic connectome for the cephalopod brain is not available today, so we want to fill that gap by mapping the connectome of the visual system of a pygmy squid, Idiosepius hallami, which measures 2 millimeters”, explains Albert Cardona, researcher at the MRC LMB in Cambridge and leader of the group.

The team chose such a small yet feature-complete animal in order to be able to study how the brain is connected via nerves to the rest of the body, such as the optic lobes, muscles to move its arms and water jet, and the skin chromatophores to control camouflage. “We hope that the data, combined with experiments in our lab using electron microscopy and connectomic reconstruction of all its central neural circuits will provide us with a full picture on the way the cephalopods’ nervous system works”, says Cardona.

It is the team’s first beamtime, and Cardona explains how they came across the ESRF: “We are here at the ESRF thanks to Alexandra Pacureanu’s work on a leg of a vinegar fly on ID16A. This had a huge impact in the field and completely changed the perception of what is possible with this technique and how it can benefit connectomics. And we are here to pursue that opportunity”, he concludes.

Top image: A scan of the pigmy squid using X-ray nanotomography on ID16A. Credits: A. Pacureanu