November 1, 2000

2 min read

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Two-headed Hydra

By Kate Wong

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Image: Courtesy of Cold Spring Harbor Laboratory

Although the result is infinitely less terrifying than the gigantic, many-headed monster of Greek mythology, scientists have succeeded in coaxing the real-life Hydra, a tiny freshwater polyp, into sprouting a second head using peptides. According to a report published in the November issue of the journal Genes & Development, the feat stems from their identification of a novel peptide dubbed HEADY. The discovery sheds light on the mysterious process by which the head end of the organism¿s body axis is established during development. Earlier research had revealed a number of signaling peptides involved in axis specification in flies, worms and mammals. The new study, conducted by Jan U. Lohmann and Thomas C. G. Bosch of the University of Jena in Germany, demonstrates that they also play a key role in directing body axis formation in lower metazoans, or multicelled animals.

Because Hydra polyps are radially symmetrical, they have only one main axis¿one that goes in the top-bottom, or apical-basal, direction. In order to pinpoint HEADY¿s involvement in organizing the body plan, the researchers conducted experiments in which they demonstrated that HEADY is expressed specifically in the apical end of the Hydra¿s body axis and that it is necessary for head formation in wild Hydra. In a third experiment, Hydra donor tissue was treated with HEADY and labeled with fluorescent latex beads. Five days after it was transplanted into a host, the fluorescent tissue developed into a second head (right), thus manifesting HEADY¿s potent ability to specify tissue fate. Taking these results into consideration, the authors conclude, "our data on the isolation and functional analysis of HEADY adds further support to the view that peptides have played a key role as developmental signals in metazoan evolution."

Kate Wong is an award-winning science writer and senior editor for features at Scientific American, where she has focused on evolution, ecology, anthropology, archaeology, paleontology and animal behavior. She is fascinated by human origins, which she has covered for nearly 30 years. Recently she has become obsessed with birds. Her reporting has taken her to caves in France and Croatia that Neandertals once called home to the shores of Kenya’s Lake Turkana in search of the oldest stone tools in the world, as well as to Madagascar on an expedition to unearth ancient mammals and dinosaurs, the icy waters of Antarctica, where humpback whales feast on krill, and a “Big Day” race around the state of Connecticut to find as many bird species as possible in 24 hours. Wong is co-author, with Donald Johanson, of Lucy’s Legacy: The Quest for Human Origins. She holds a bachelor of science degree in biological anthropology and zoology from the University of Michigan. Follow her on Bluesky @katewong.bsky.social

More by Kate Wong

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