Porpita porpita, commonly known as the blue button, is a marine organism consisting of a colony of hydroids found in tropical waters from California to the tropical Pacific, the Atlantic and Indian oceans It is often mistaken for a jellyfish, but although jellyfish and the blue buttons are part of the same phylum (Cnidaria), the blue button is part of the class Hydrozoa.
Gallery: Jaw-Dropping Images of Life Under the Sea
Pasquale Vassallo captured this image of crabs tending to a barrel, or frilly-mouthed, jellyfish in the Gulf of Naples, Italy. "Over the past few months, my photographic work has focused primarily on the large presence of species of jellyfish Rhizostoma pulmo, in the Gulf of Naples. In this picture a couple of crabs, Liocarcinus vernalis species, are its tenants. When the jellyfish rub the sandy seabed, the crabs jump on it and get carried to different areas," Vassallo said.
Baby Jellies by Peter Willows/BNPS, telegraph.co.uk: Hundreds of moon jellyfish babies have been born at the Weymouth Sealife centre in Dorset. Aquarists say they have never seen so many jelly babies of all shapes, sizes and colours from many different species at one time - but even though they may look cute many of them are highly poisonous as well. #Moon_Jellies
10 Stunning and Unique Jellyfish Species From All around the World