In the Gulf of Bizkaia, with confusions between species everywhere, we can find examples of jellyfish of the genus Rhizostoma, so well known in summer. In the Cantabrian we can find two species of this group: Rhizostoma octopus (Gmelin, 1791) and Rhizostoma luteum (Quoy et Gaimard, 1827). However, the name of the jellyfish Rhizostoma pulmo (Macri, 1778) found in Mediterranean waters has sometimes been used. So we could also talk about the Atlantic copy of R. octopus R. pulmo.

As with living notes, it is not an easy group to investigate, but in the last decade great advances have been made in the research of its life cycle. Although there will be young specimens in all species of the genus Rhizostoma, they are difficult to observe since they are 3 to 4 cm clear jellyfish. Adult bells, however, may be over 150 centimeters in diameter and there are jellyfish over 25 kg.

R. octopus is the immense jellyfish that we can find in the Cantabrian and Zurriola, Saturraran or Ondarraitz that caresses. Although in many places and languages it is known as “Kupel jellyfish”, “Mar Lung” or “Cauliflower”, in our case it is “Blue Bell”. To the north of our warm sea, for example in the Irish Sea, it is easier to observe it in large groups, while here, individually and in small quantities. Skin turtles and lunar fish are lovers of this jellyfish and perform thousands of marine miles in search of this prey, visiting the cold northern waters.

The blue bell can have different colors throughout your life: white or yellowish, green, blue, pink or brown. But it has a purple crown that deserves special attention: it decorates the entire edge of the bell giving color to its 112 rounded lobes. In addition, the eight oral arms under the hood are indicative for the identification of the species, with a structure in the form of a cauliflower. In these arms they have hundreds of small tentacles, provided with urticating cells called nematocysts that will use them for hunting and defense.

The other bell we can find in our waters is the white bell (R. luteum). It has been missing for many years, because it has been misidentified, by being confused with other members. The white bell is more abundant than expected, from the Cantabrian Sea to South Africa.

Two characteristics stand out among them: a violet crown on the edge of the bell and the morphology of the arms of the mouth. The blades of the white bell have the shape of a long tassel, which can reach three meters in length, usually pale yellow, with purple tones at its end.

Notice, then, if next time we see jellyfish at sea, not all of them are the same.