Because most jellyfishes are venomous, they are also called sea wasps or marine stingers. Each tentacle contains more than 100,000 cnidocytes with nematocysts, small needles that inject venom into the victim. The most dangerous species are found in the tropical Indo-Pacific but the Caribbean species can also cause serious injuries. This picture was taken in Guadeloupe (French West Indies) by Dominique Marion, a senior scientist from the Institut de Biologie Structurale in Grenoble, France. Visit his galleries at for more underwater pictures.