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Jellyfish species (Cnidaria)
Hydrozoa species (Cnidaria) medusa, or jellyfish.
Jellyfish invasions--mediated by humans--have been reported all around the world, and the ballast water from ships has been recognized as a main source of these marine invasions. Ships take on ballast water, needed for stability, in originating harbors. In destination harbors, ships may dump their ballast water along with accompanying organisms, including jellyfish. Jellyfish that are released into non-native habitats may colonize them--particularly if they face few or no predators in these areas. Some invasions have dramatic economic and ecological consequences while others, especially in the marine realm, can go unnoticed.
Maria Pia Miglietta, a research professor from the University of Notre Dame, has identified a human mediated, worldwide introduction to the hydrozoan species Turritopsis dohrnii. The normal life cycle of hydrozoans involves the asexual budding of the medusa, or jellyfish, form from colonial polyps. But the medusae of T. dohrnii, when starved or damaged, are able to revert their life cycle back to the polyp stage through a process called transdifferentiation, allowing them to easily survive long journeys in cargo ships and ballast waters. This potential immortality of T. dohrnii could have devastating consequences for the fishing and tourist industries.
To learn more about the increase in jellyfish populations worldwide and the problems they are causing, see the NSF Special Report "Jellyfish Gone Wild!" (Date of Image: 2007)
Credit: Maria Pia Miglietta, Pennsylvania State University
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