Topic: Cephalopods – Cephalopoda

  • Blekksprut 10-01-2017_2.jpg
    Photo: Erling Svensen / IMR
  • Eledone cirrhosa 07-2015 (18).jpg

    Common sqid (Eledone cirrhosa).

    Photo: Erling Svensen / IMR
  • Eledone cirrhosa 09-2015 (7).jpg

    Eight-armed octopus.

    Photo: Erling Svensen / IMR
  • Sepia officinalis - shell 16-12-2014_2.jpg

    Shell from Sepia.

    Photo: Erling Svensen / IMR

Cephalopods are an ancient group of animals that have existed for about 500 million years. Like bivalves and gastropods, they belong to the class Mollusca, although their relationship is not necessarily obvious. 


 

Most of today's cephalopod species have a soft body with no outer hard parts, but an inner shell that stiffens the body and regulates buoyancy. 

The Greek word "Cephalopoda" means head-feet and refers to the feet or arms sitting directly on the head. There are around 800 species in the world, and it is an exclusively marine group. Species diversity is highest around the equator and decreases towards the poles. We can distinguish between eight- and ten-armed cephalopods. The ten-armed ones have two tentacles in addition to the eight arms, and these are often longer and thinner than the arms.

In Norwegian waters, we find about 25 species, some of which are very rare and verified by only one or a few individuals. They can be divided into four main groups: 

  • eight-armed cephalopods with and without fins (at least 5 species) 
  • ten-armed cephalopods with torpedo-shaped mantle (most species and individuals, can get large) 
  • ten-armed cephalopods with round mantle (9 species, small species) 
  • ten-armed cephalopods with oval mantle and calcified inner shell (at least 1 species) 

Many species have commercial value and are exploited as food in other parts of the world.
 

The main groups of cephalopods in Norwegian waters: