What is the difference between a squid and a cuttlefish?

Squids and cuttlefishes are both cephalopods and have some similarities in their appearance, but there are a few key differences between them.

The first difference is in their physical appearance. Squids have a long body and ten arms, while cuttlefish have a shorter body with eight arms and two tentacles. The tentacles of a cuttlefish are shorter than those of a squid. Additionally, cuttlefish have a more rounded body shape than squids, which are more cylindrical.

The second difference is in their internal anatomy. Squids have a hard, internal shell called a pen, while cuttlefish have a soft, internal shell called a cuttlebone. The cuttlebone is filled with gas and helps the cuttlefish regulate its buoyancy.

The third difference is in their behavior. Squids are known for their speed and agility, and are active hunters. Cuttlefish, on the other hand, are known for their ability to camouflage themselves and blend in with their surroundings. They are often ambush predators that wait for their prey to come to them.

Overall, while squids and cuttlefishes share some similarities, there are clear differences between them in terms of their physical appearance, internal anatomy, and behavior.