Marine animals need to make important decisions during their life for which they rely on sensing the environment around them. Such decisions include migrating from one area to another to find food and shelter and performing defensive or offensive manouvers to avoid a predator or to hunt for prey. Importantly, A large fraction of marine organisms need to make an even bigger and irreversible decision during their lifetime, which is to determine when and where to metamorphose from a larva to an adult. Metamorphosis is associated with dramatic changes in physiology, body shape and behavior. These decisions are made based on sensing and assessing the valence of a wide range of sensory cues in the sea that animals need to detect and respond to. In this project we will use the larva of Ciona intestinalis which has a small nervous system (about 300 neurons) to ask a number of questions including the following:
What are the sensory stimuli that promote or inhibit metamorphosis of marine larvae?
What types of neurons and molecules are used to sense these stimuli?
Finally, what are the behavioral actions that the swimming larvae need to execute during and after sensing stimuli that promote or inhibit settlement and metamorphosis?
To address these questions, we will use a number of techniques including advanced microscopy, deep learning based behavioral analysis and genetics.
In his book ‘’The Voyage of the Beagle’’ Charles Darwin notes the story of a man named Renous. He was a German naturalist who was arrested in the 1830s in San Fernando of Chile for heresy. The reason for been deemed a heretic was that he claimed he could turn a caterpillar into a butterfly! Today, it is well established that what he described was the amazing phenomenon of metamorphosis, a developmental process through which numerous animals will transform their bodies at the end of their larval life.
While several aspects of the developmental and hormonomal mechanisms underlying metamorphosis have been extensively studied across species, the sensory molecules and neuronal computations that permit an organism to sense settlement cues and leverage that information in order to decide whether to enter the irreversible process of metamorphosis are still largely unknown. This lack of understanding of the neuronal substrates of such wide-spread developmental mechanism in numerous metazoans represents a major knowledge gap.
Our project will use the larva of Ciona intestinalis, one of the closest living relatives to all vertebrates with the aim of answering the general question of how an animal's nervous system leverages sensory information in order to initiate the process of settlement and metamorphosis in a permissive environment that will ensure its survival. This animal has a fully mapped compact nervous system composed of only a few hundred neurons. It is transparent facilitating functional imaging and it is amenable to genome editing.
By using an interdisciplinary approach combining molecular biology with computational neurobiology, high-throughput behavioral analysis and sensory stimulation coupled functional imaging of individual neurons as well as of the entire larval brain we will have an unprecedented chance to unravel the molecular and neuronal code that determines settlement decisions and initiates larval metamorphosis.