pääjalkaiset

Pääjalkaiset is the Finnish word for cephalopods, a class of marine molluscs. This group includes intelligent and highly adapted animals such as octopuses, squids, cuttlefish, and the nautilus. Their name, derived from Greek words meaning "head-foot," refers to their most distinctive characteristic: their tentacles or arms are attached directly to their heads.

Cephalopods are known for their advanced nervous systems, complex eyes, and remarkable ability to camouflage themselves. They possess a mantle, a muscular outer layer that encloses their internal organs. Many species also have a shell, though in most modern forms, this shell is internal (like in cuttlefish) or has been reduced or lost entirely (like in octopuses and squids). They move using jet propulsion, expelling water from a siphon.

These marine invertebrates inhabit oceans worldwide, from shallow coastal waters to the deep sea. They are primarily predators, using their tentacles to capture prey. Their diets vary widely depending on the species and habitat, including fish, crustaceans, and other molluscs.

The intelligence of cephalopods is a subject of ongoing scientific research. Octopuses, in particular, have demonstrated problem-solving abilities, learning capabilities, and complex behaviors that set them apart from other invertebrates. Their unique evolutionary path has resulted in a diverse array of fascinating and highly specialized marine creatures.