Jellies Reveal Evolutionary History (Image 2)

The comb jelly Aulicoctena, a deep-sea species that was collected using a remotely operated underwater vehicle by the Monterey Bay Aquarium Research Institute.

A National Science Foundation-supported study has defined the earliest splits at the base of the animal tree of life, a hierarchical representation of the evolutionary relationships between species that was introduced by Charles Darwin. Results of the study suggest that the comb jelly, which has tissues and a nervous system, split off from other animals before the tissue-less, nerve-less sponge--a finding that challenges the traditional view of the base of the tree of life, which placed the sponge as the earliest diverging animal.

The presence of the relatively complex comb jelly at the base of the "tree" suggests that the first animal was probably more complex than previously believed, says Casey Dunn of Brown University, who led the study.

While Dunn cautions that additional studies will be needed to corroborate his team's findings, he says that the comb jelly could only have achieved its apparent seniority over the simpler sponge through one of two new evolutionary scenarios: 1) the comb jelly evolved its complexity independently of other animals, after it branched off onto its own evolutionary path; or 2) the sponge evolved its simple form from more complex creatures. [Research supported by NSF grants DEB 04-08014, DEB 03-34932 and DEB 05-31757.]

To read more about Dunn's research, see the NSF Press Release, "And the First Animal on Earth Was a ..."

To learn more about the basics of jellyfish biology, what scientists have learned thus far about the worldwide increase in jellyfish populations, and the causes of jellyfish swarms and how they effect both human and marine life, see the NSF Special Report, "Jellyfish Gone Wild!" (Date of Image: 2005) [See related image Here.]