Scientists in Norway have performed tissue transplants on comb jellies and found that these gelatinous creatures use the same kind of body organizing system as frogs and fish. The discovery suggests that the ability to coordinate a body plan may be far older than anyone thought.
A tiny transplant that rewrites animal history
Researchers at the Sars International Centre for Marine Molecular Biology in Bergen took small pieces of tissue from one comb jelly embryo and grafted them onto another. The transplanted tissue acted as an organizer, telling the host embryo where to build a head and where to grow a tail. This is the same kind of signaling that happens in vertebrate embryos, but comb jellies are among the most ancient animal lineages alive today.
Why a jellyfish relative matters for understanding ourselves
Comb jellies, or ctenophores, are not true jellyfish. They are a separate branch of the animal tree that split off before sponges, before corals, and before anything with a backbone. For decades, biologists assumed that the organizer system evolved later, in more complex animals. The Norwegian team showed that comb jellies have it too, which means the genetic toolkit for building a body may have been present in the very first animals.
The experiments were led by Ruth Styfhals and Pawel Burkhardt. They worked with the species Mnemiopsis leidyi, a common comb jelly found in coastal waters. The team removed a cluster of cells from the margin of one embryo and placed it into a different spot on another embryo. The host embryo then developed a second set of body structures, proving that the transplanted cells carried instructions that could override the host's own developmental program.
Local researchers in Norway care because the country's fjords are rich in comb jellies, making Bergen a natural hub for studying these animals. The work also challenges long held assumptions about evolution. If comb jellies share this organizer mechanism with vertebrates, then the common ancestor of all animals likely had it too. That ancestor lived more than 600 million years ago.
The findings were published in Nature. They do not prove that comb jellies are more complex than previously believed. They show instead that a fundamental piece of developmental machinery is shared across vast evolutionary distances. What looks like a simple jelly may carry the same ancient instructions that shape our own bodies.
