A Siphonophore caught in the North Sea viewed from above.

  • Taxonomy

    Kingdom: Animals

    Phylum: Cnidaria

    Class: Hydrozoa 

    Order: Siphonophores (Siphonophorae)

  • Location

    Marine waters, worldwide.

  • Size

    a few millimetres to tens of metres in length


Siphonophores are spectacular animals. Not only do they often look bizarre, they are also exceptionally built. A Siphonophores  consists of a colony of individual polyps. The individuals can have different tasks such as collecting food (gastrozoids), providing buoyancy (pneumatophore), providing propulsion (nectophore) or reproduction (gonophore). 

 Most Siphonophores  float in the water, aided by the pneumatophore, a vesicle with gas in it. Some, such as the notorious Portuguese man-o-war, have a floating body with which they float on the surface of the water. Most Siphonophores  are carnivores and have stinging cells to catch prey like fish, copepods and other crustaceans. They can also be dangerous to humans at times!

 Siphonophores  are often very fragile and in a plankton net they usually fall apart completely, so you can only find some loose nectophores. Fortunately, the shape of the nectophores is often characteristic for a certain species. 

Siphonophores are rare in Dutch waters; they are mainly animals from the open ocean. In 2018, however, we found quite a number of small Siphonophores in the North Sea!

Siphonophores caught in the North Sea, probably Nanomia cara. The nectophores have been released.

A Siphonophore caught in the North Sea viewed from above, with a number of loose nectophores included.