A golden age of gelata: past and future research on planktonic ctenophores and cnidarians

Abstract

The study of the natural history of gelatinous zooplankton (‘gelata’) reached a high point at the end of the 19th century, when scientists first began to understand the phylogenetic and ecological links between cnidarians and ctenophores. Siphonophores, carefully figured in their entirety, and gauze-like lobate ctenophores too fragile to touch, were described by the dozens. In the ensuing years, focus on zooplankton shifted toward more ‘industrial’ goals such as quantitative sampling using plankton nets. While plankton scientists were busy summing tattered parts, they lost sight of the whole jellies themselves, and a crustaceocentric view of the ocean came to dominate. During this period, the most dramatic breakthroughs in cnidarian research came from laboratory studies of neurobiology, physiology, and development, particularly of certain model organisms. Now, at the turn of this century, we have the opportunity to bring gelata back into primacy. Submersibles and remotely operated vehicles allow us to study entire life histories of organisms that we did not even know existed. The tools of molecular biology allow us to answer questions about development, evolution, and phylogeny that had reached a stalemate. Even in the surface waters, where it might be thought that there is little left to learn, in situ observations have revealed unexpected interactions and hidden diversity. The critical roles that these organisms play in the health of the oceans, their position at the crux of many evolutionary debates, and the tools for biotechnology that they provide, have led to resurgent public appreciation and awareness. Although advanced tools do not necessitate good science, we have few excuses for failing to bring about another golden age of gelata.