Types of Cephalopods

Cephalopods can "change color faster than a chameleon." These changeable mollusks are active swimmers who can quickly change color to blend in with their surroundings. The name cephalopod means "head-foot" because these animals have tentacles (feet) attached to their head.

The group of cephalopods includes such varied animals as octopus, cuttlefish, squid, and nautilus. In this slideshow, you can learn some facts about these interesting animals and their behavior and anatomy.

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Chambered Nautilus / Stephen Frink / Image Source / Getty Images
Stephen Frink / Image Source / Getty Images

These ancient animals were around 265 million years before dinosaurs. Nautilus is the only cephalopod that have a fully-developed shell. And what a shell it is. The chambered nautilus, shown above, adds internal chambers to its shell as it grows. 

The nautilus's chambers are used to regulate buoyancy. Gas in the chambers can aid the nautilus in moving upward, while the nautilus can add liquid to descend to lower depths. Coming out of its shell, the nautilus has over 90 tentacles that it uses to capture prey, which the nautilus crushes with its beak. 

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Octopus (Octopus cyanea), Hawaii / Fleetham Dave / Perspectives / Getty Images
Fleetham Dave / Perspectives / Getty Images

Octopus can move quickly using jet propulsion, but more often they use their arms to crawl along the ocean bottom. These animals have eight sucker-covered arms that it can use for locomotion and for capturing prey.

There are about 300 species of octopus; we'll learn about a very poisonous one in the next slide. 

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Blue Ringed Octopus

Blue Ringed Octopus / Richard merritt FRPS / Moment / Getty Images
Richard merritt FRPS / Moment / Getty Images

The blue ring or blue-ringed octopus is beautiful, but also deadly. Its beautiful blue rings can be taken as a warning to stay away. These octopuses have a bite so slight that you might not feel it, and it might be possible for this octopus to transmit its venom even through contact with its skin. Symptoms of a blue ring octopus bite include muscular weakness, difficulty breathing, and swallowing, nausea, vomiting and difficulty speaking.  

This toxin is caused by bacteria - the octopus has a symbiotic relationship with bacteria that produce a substance called tetrodotoxin. The octopus provides the bacteria with a safe place to live while the bacteria provides the octopus toxin that they use for defense and to calm their prey. 

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Common Cuttlefish, Sepia officinalis / Schafer & Hill / Photolibrary / Getty Images
Schafer & Hill / Photolibrary / Getty Images

Cuttlefish are found in temperate and tropical waters, where they are excellent at changing their color to blend in with their surroundings. 

These short-lived animals engage in elaborate mating rituals, with males putting on quite a show to attract a female. 

Cuttlefish regulate their buoyancy using a cuttlebone, which has chambers that the cuttlefish can fill with gas or water. 

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Scuba Diver with Humboldt Squid (Dosidicus gigas) at Night/Franco Banfi / WaterFrame / Getty Images
Franco Banfi / WaterFrame / Getty Images

Squid have a hydrodynamic shape that allows them to swim quickly and gracefully. They also have stabilizers in the form of fins on the side of their body. Squid have eight, sucker-covered arms and two longer tentacles, which are thinner than the arms. They also have an internal shell, called the pen, which makes their body more rigid.

There are hundreds of species of squid. The image here shows a Humboldt, or jumbo squid, which lives in the Pacific Ocean and got its name from the Humboldt current which lies off South America. Humboldt squid can grow to 6 feet in length.

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Kennedy, Jennifer. "Types of Cephalopods." ThoughtCo, Aug. 26, 2020, thoughtco.com/types-of-cephalopods-2291910. Kennedy, Jennifer. (2020, August 26). Types of Cephalopods. Retrieved from https://www.thoughtco.com/types-of-cephalopods-2291910 Kennedy, Jennifer. "Types of Cephalopods." ThoughtCo. https://www.thoughtco.com/types-of-cephalopods-2291910 (accessed June 10, 2023).