Jellyfish outbreaks: A Mediterranean focus on a global threat.

The venomousness of Cnidaria is a subject of concern having great influence on human activities and public health. Notably, during jellyfish outbreaks some activities of economical concern, such as fishing and tourism, can be compromised. In some regions across the globe venomous jellyfish are known to be a very important sanitary problem, some of them being able to cause serious symptoms with erythema, vesicles, redness, swelling, and further dermonecrotic, cardiotoxic, and neurotoxic effects. These reactions are particularly dangerous and can be lethal in sensitive subjects. Conversely, in the Mediterranean Sea extensive studies about the morphology, the biology, and the ecology of cnidarians were carried out, albeit the toxicological research on cnidarian venoms was scarcely developed until the 1980s. This is in part due to the fact that these studies were not of great interest for human pathology due to the weak poisonousness of Mediterranean jellyfish and anemones. In spite of this, during jellyfish blooms, which occurred from late 1970s to early 1980s and after the subsequent recurrent outbreaks, jellyfish stinging caused several problems throughout the Mediterranean region. As a consequence, several research papers focused on this subject were provided and the research fast developed. In this paper the available data on jellyfish outbreaks, with an emphasis on the situation of the Mediterranean Sea, are reviewed and discussed examining the possible relationships with environmental global threats, such as the Global Change, and taking into consideration the effects on humans.