While you might not be familiar with the term “cephalopod” you are probably familiar with some of the animals that fall into this category. cephalopods are actually highly specialized molluscs, or mollusks, and include animals like octopuses, squids, cuttlefish and nautiluses. In this article, we will be covering the different types of cephalopods.
There are four main types of cephalopods, and many of them share similarities. We will talk about what makes a cephalopod a cephalopod, the different groups, and give you several examples.
What is a cephalopod?
The word for cephalopod in greek means “feet-head”. This group of invertebrates has arms or tentacles attached to their head, officially referred to as mantle. They are strictly marine organisms and therefore can only be found in saltwater. They are regarded as the most intelligent invertebrates and there have been several studies dedicated to exploring cephalopod intelligence. In fact, octopuses have several brains!
Cephalopods tend to be excellent hunters, using fast moving strikes of their arms and tentacles to ambush their prey. In presence of a threat, all but the nautiluses may expel a thick cloud of dark ink to distract predators. This has earned them the name “inkfish” with fishermen.
These incredible animals are also masters in camouflage and can change their colors and patterns to expertly blend in with their surroundings. Some have such good control over their ability to change colors that they can change on only one portion of their body, displaying two or more different patterns at a time.
Four types of cephalopods
1. Octopuses
Number of species: ~300
Octopuses are arguably the most well-known cephalopods, known for their large mantles and eight strong arms covered with powerful suction cups. These incredible animals are very intelligent and have a total of nine brains! They have a central brain and then a brain for each arm.
In addition, octopuses also have multiple hearts.
Octopuses can have an arm span that reaches just under three inches across, or have an arm span that spreads out across over 15 feet! Interestingly enough, all octopuses are actually venomous- however not all have very toxic or potent venom and luckily envenomations are incredibly rare.
These eight-legged creatures can be found in oceans and conditions all throughout our blue planet. Some species can withstand the frigid temperatures of arctic water while others prefer warm, tropical seas.
2. Squids
Number of species: ~300
Squids are another group of fascinating mollusks that have eight arms (like octopuses) and two tentacles. They have elongated mantles with large eyes that are approximately 100 times larger than those of human eyes in relation to body size. Their large eyes and pupil shape allow for squids to see crisply and clearly with a line of vision that nearly circles their entire body.
Overall, squids are a mysterious group and there are still many questions to be answered about how they live their lives and their biology and ecology. There are species that can be found throughout all of our seas and oceans. Some prefer warm, shallow waters while others inhabit incredible depths and cold water.
Squids are economically important in the fisheries as they are commonly caught, sold and served in restaurants. One common dish, calamari, is fried squid that is sold in restaurants all over the world.
3. Cuttlefish
Number of species: ~120
Cuttlefish are an interesting, almost alien-like sea creature that looks like a cross between an octopus and a squid. Like squids, they have eight arms and two tentacles. Their tentacles are equipped with strong suction cups that allow them to grab hold of their prey.
Generally, cuttlefish are smaller than some of their relatives, with the largest species only growing up to about 20 inches. They are preyed on by dolphins, sharks, fish, seals, seabirds and sometimes other cuttlefish. Cuttlefish are not as widely spread as squids or octopuses, and only inhabit tropical and temperate waters.
Like octopuses, cuttlefish are incredibly intelligent. In fact, they have one of the largest brain to body size ratios of any invertebrates. In addition to their intelligence, cuttlefish have an enhanced ability to change colors. They are able to display up to 12 different patterns on their mantle at a time. This allows them to communicate with other cuttlefish as well as blend in with their surroundings.
4. Nautiluses
Number of species: ~6
There are very few species of Nautiluses and many people are not familiar with them. They are fairly mysterious and are rarely seen. They are pelagic organisms, meaning that they inhabit the open ocean rather than shallow, coastal waters.
Unlike their relatives, nautiluses have an external shell which they can withdraw themselves completely into. Nautiluses shells have several chambers inside that combined with it’s spiraled shape, allows for nautiluses to withstand extreme pressure while in deep water. They can survive up to about 2,600 feet before being crushed.
They have many tentacles, up to 60 of them, opposed to the 8-10 arms and tentacles that other cephalopods have. Nautiluses do not have suction cups, but instead have many, small ridges on their tentacles that allow them to tightly grip onto things.
Check out this article for 12 examples of cephalopods with pictures and interesting facts about each one.
Samantha is a wildlife biologist with degrees in animal behavior and environmental biology. Most of her work has been with reptiles, however she has also worked with birds and marine organisms as well. She enjoys hiking, snorkeling, and looking for wildlife.