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Cephalopod Awareness Days: What is a Cephalopod?


Cephalopod Awareness Days: What is a Cephalopod?

October 8, 2016

Written by Imogen Farris, Public Relations Coordinator 

A cephalopod, pronounced “seph-a-lo-pod,” is a category of invertebrates consisting of some of the most intelligent and exotic creatures. Cephalopods have a completely merged head and foot, typically with a ring of arms or tentacles around the head. Cephalopod, meaning “head-foot,” is a smaller subgroup of mollusks.

From masters of disguise to suction-cupped tentacles, the octopus, cuttlefish, squid and nautilus make up this unique category of animals. We’re excited to highlight them from Oct. 8-12 in observance of Cephalopod Awareness Days. But what exactly differentiates one unique cephalopod from another? Find out below:

First, which animals are cephalopods?
Typically, an octopus has a short, round body with eight tentacles. Like other cephalopods, the octopus has a beak, with its mouth at the center point of the arms. Since the octopus has no internal or external skeleton, it is able to squeeze through tight places. For protection, an octopus has the ability to release a stream of ink, use camouflage, and jet quickly through the water.

Similar to the cuttlefish, squid also have eight tentacles and two, typically longer, tentacles. Squid have long bodies with an internal shell. Squid also have skin covered in chromatophores, which allows for excellent camouflage from both prey and predators. In order to get around, squid use jet propulsion. This means water is sucked in and expelled out in a fast, strong jet. They can also change the direction of the expulsion, allowing them to travel any direction.


Despite having the word “fish” in its name, the cuttlefish is actually a mollusk! This cephalopod has an internal shell, called a “cuttlebone,” that helps control buoyancy. It’s ability to rapidly change color, thanks to chromatophores that cover its skin, allows the cuttlefish to camouflage and blend into its surroundings. When threatened, the cuttlefish releases a cloud of ink into the water, giving it a chance to escape. This cephalopod has eight tentacles and two extendable tentacles used to grab prey and pull it into its mouth.

The nautilus typically has the most tentacles of all other cephalopods – sometimes up to 90 tentacles! They have a powerful grip and a parrot-like beak made up of two interlocking jaws used to help rip crustaceans from rocks. The nautilus is the only cephalopod with an external shell, allowing the animal to withdraw completely inside it, using its tentacles to seal the opening. Compared to other cephalopods, the nautilus has the worst vision, and is instead thought to use its sense of smell to find food.

What makes a cephalopod a cephalopod?

The eyes on a cephalopod are quite large for their body size! The octopus’s eye is slit shaped with a rectangular pupil, while the cuttlefish has a “w” shaped eye. Squid typically have a round eye. The nautilus has the simplest eye of all cephalopods – it is mounted on a stalk with no lens and a small pupil.

Not all cephalopods have shells, but many have internal shells, including squid, cuttlefish, and octopuses. The nautilus is the only cephalopod with an external shell. This shell helps with protection, while internal shells can help with support and buoyancy, allowing the animal to float easily in the water column.

All cephalopods have tentacles, but not all have arms! Octopuses, cuttlefish, and squid have eight non-retractable arms, but only cuttlefish and squid and the nautilus have tentacles. The arms can have suckers and sometimes hooks. Both squid and cuttlefish also have two tentacles that they use to strike quickly at prey and then bring food into their mouths. The nautilus is the only cephalopod without arms, but it may have up to 90 tentacles!

Changing Colors
All cephalopods, except the nautilus, can change colors, using pigment-filled cells on their skin called chromatophores. These chromatophores expand and contract, which will reveal or conceal small dots of color. This expansion and contraction gives the illusion of changing color. The chromatophores are so small that 200 may be found on a patch of skin the size of a pencil eraser! Cephalopods change colors for a variety of reasons, but primarily for camouflage and courtship rituals. 

There is much to learn about cephalopods and we hope you can join us in celebrating these remarkable animals from October 8-12. Activities are included in Total Ticket Admission.
Learn more about these one-of-a-kind creatures in our Animal Guide.

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