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Blue Dragons in Pemba

22nd November 2018

In August 2018, following strong winds, a number of tiny sea slugs, known as blue dragons, washed up on a beach in north Pemba. Read on to find out more about one of the sea’s poisonous and fascinating creatures!


[August 2018] The Blue Dragon, Latin name Glaucus atlanticus, is found throughout the world’s tropical oceans. They can reach 6 cm and have three pairs of “arms” with stinging rows of tentacles. These tiny sea slugs are pelagic, meaning they live in the open ocean. They spend the majority of their lives floating upside down on the surface of the sea, carried by wind and currents, staying afloat by a gas bubble in their stomach.

The species feeds on colonial marine organisms known as “siphonophores”, many of which are venomous and resemble jellyfish. The Blue Dragon feeds almost exclusively on a particular species of siphonophore, known as the Portuguese Man-of-War (Physalia physalis) from which it extracts the stinging nematocyst cells. They therefore have an extremely painful sting, so if you are lucky to encounter one of these sea dragons be sure not to touch and just observe their beauty!


The species has a great way of camouflaging itself against potential predators. From above, they display their blue and white surface making it difficult for predators such as birds to see them. The side which faces down into the water is silvery-grey and camouflages them well against the surface of the water making it hard for fish to spot them.

They are rarely seen, except on days of high onshore winds, which cause them to be blown onto beaches, which is what happened at the Manta Resort in August. Along with a lot of Portuguese Man-of-War these tiny sea dragons had washed up on the beach during the high tide. The four individuals we found were carefully transferred from the sand to a glass filled with seawater along with one of the Portuguese Man-of-War. This gave them an opportunity to revive themselves and for us to take some close up photos. When the tide had retreated we returned them all to the sea where they are hopefully continuing to roam the seas, blown about by the wind and currents.