Gap junctions are formed by innexins in a wide range of invertebrates, including the model organisms Drosophila and Caenorhabditis. Multiple innexins have been identified in the Hydra genome and innexin-1 has been shown to form gap junctions in ectodermal epithelial cells6,7. We now show by in situ hybridization that innexin-2 is expressed in a small group of nerve cells in the lower body column of Hydra and that an anti-innexin-2 antibody binds to gap junctions in the same region. Treatment of live animals with innexin-2 antibody eliminates gap junction staining and strongly reduces spontaneous body column