Overview
Cephalopods are one of the most interesting groups of molluscs due to their high level of organisation and their complex behaviour patterns. They include the largest invertebrates found in the world: the giant and colossal squids. Cephalopods are found in all oceans, from tropics to the polar regions, and at all depths from the intertidal to deep oceanic trenches. None are found in freshwater.
The cephalopod body is characterised by the development of the original single foot into a series of large prehensile tentacles or arms at the anterior end, which surround the head.
As well as squid and octopuses, the cephalopoda includes the cuttlefish and nautiluses, which do not occur in New Zealand waters. The shells of the subtropical to warm temperate "paper nautilus" are occasionally found on beaches as far south as Otago. However, these shells are the brood chamber produced by female Argonauta - a genus of pelagic octopus. Numerous "ram's-horn" shells are commonly found after strong onshore winds. These ram's-horn shells are the chambered, internal buoyancy organ of the squid-like Spirula, which lives pelagically in the deep oceans. The gas-filled chambers keep the animal floating vertically and the shells wash ashore after the animal dies: intact animals are very rarely found beachcast.
NB: octopuses, octopi and octopodes are all accepted as plural terms for octopus!