Cute but dangerous

The jellyfish Olindias sambaquiensis Muller, 1861 is common in the Southeastern and Southern costs of Brazil, especially during winter and spring. Behind its beautiful, vivid colors and graceful swimming there is a danger: it stings beachgoers and swimmers. Although most accidents are mild or harmless, they are painful; this species is responsible for about 80% of the accidents caused by marine organisms in the Southern and Southeastern coasts of Brazil (Vidal Haddad Jr., pers. commun). The umbrella of an adult specimen may reach 10 cm wide. Around the umbrella margin there are 3 types of tentacles. The dark red or brownish primary tentacles are relatively short and rigid, and are inserted above bell margin; they are usually kept still, being provided with cnidocyst clusters in transverse or oblique clasps (do not completely clasping the tentacles). The bright yellow secondary tentacles are inserted on the bell margin, being long, thin and very extensible; they are provided with complete or incomplete