Taurine-driven chemotaxis and metamorphosis in ascidian tadpole larvae.

Settlement of marine invertebrate larvae at suitable sites for metamorphosis, growth, and reproduction is crucial for propagating populations, but often causes ecological problems such as bioinvasion and biofouling. Chemosensation plays an essential role in larval settlement preferences. However, the mechanisms for sensing chemical cues underlying these preferences remain unknown. Using urochordate ascidian larvae, the prominent marine fouling organisms affecting coastal ecosystems, we explored the mechanism of larval chemosensation and its role in settlement preference. Here, we identified taurine, a specific sulfur-containing amino acid secreted from marine adult animals, as a chemical attractant for ascidian larvae to locate salubrious environments for metamorphosis. Taurine stimulates primary sensory neurons within larval papillae, and this neuronal excitation is integrated in the simple brain (also known as sensory vesicle) to elicit chemoattraction and attachment of swimming larvae. We discuss the implications of this study in the emerging field of marine Eco-Evo-Devo research by establishing a model system for understanding developmental mechanisms in the context of marine ecosystems and aquaculture. Of interest is the potential development of antifouling strategies by targeting taurine chemosensation.