It's cephalopod week! Cephalopods are amazing marine animals classified within the molluscs. In marked contrast to their clam or snail relatives though, cephalopods pack the largest brains of any invertebrates and are capable of moving by jet propulsion.

Physically, cephalopods are distinguished by having a beak, tentacles, and blue blood (due to the presence of copper-based hemocyanin for oxygen transport).

Cephalopoda is divided into the two subclasses Nautiloide and Coleoidea shown here, based on the presence or absence of an external shell.

Nautiloidea

nautilus

Coleoidea

octopuses

cuttlefish

squid

"vampire squid"

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