How Octopuses Thrive Without Bones: The Advantages of Being an Invertebrate

Octopuses are members of the Cephalopoda class in the Mollusca phylum, which contains creatures that have neither a skeleton nor a backbone. Instead, they have what is known as a hydrostatic skeleton. Unlike vertebrates, including humans and other mammals, octopuses are invertebrates, with soft, boneless bodies, relying on their hydrostatic skeleton, which uses water pressure to move and maintain their shape.

Anatomy of the Cephalopod

Cephalopods are a class of marine mollusks including octopuses, squid, and cuttlefish. They are characterized by their arms or tentacles, bearing suckers or hooks, which are directly attached to their head. They also have a well-developed head with complex eyes and a beak-like jaw. The mantle is a muscular, bag-like structure that encloses and protects the animal’s internal organs, including the gills, digestive system, and reproductive organs. It also plays a key role in respiration and locomotion through the process of jet propulsion. 

As mollusks, the octopus has the classification’s three main features: a trio of blue blood-pumping hearts with copper-rich blood, a layer of slime covering its epidermis, and DNA that links it to shelled animals. The cephalopod’s evolution is marked by a transition from shelled ancestors to diverse forms with complex adaptations, including the loss of the outer shell in many lineages.

The octopus is an invertebrate, which means it does not have an exoskeleton. Invertebrates lack a spine, vertebral column, and other bones. Invertebrates include crabs, sea sponges, insects, snails, worms, jellyfish, squid, nautiluses, and cuttlefish.

Although some octopuses always swim, many walk on their eight arms, which have hundreds of suction cups used to pick up objects.

Why Octopuses Need No Bones

Invertebrates lack bones or a spinal infrastructure, and while this would be detrimental to most animals, it’s a feature the octopus uses to its advantage. Because they lack a rigid skeleton, octopuses can get into spaces that would seem impossible, especially considering their size. The feature affords them the flexibility to contort their bodies in amazing ways.

Octopuses are an extremely ancient species. The oldest known fossils are of an animal that lived almost 300 million years ago. That specimen, of the species Pohlsepia, is on display at the Field Museum in Chicago. It is said to look similar to a flattened cow patty or a blob.

As aquatic animals, octopuses don’t need bones. Instead, they use buoyancy and the extreme musculature in their arms to move, swim, and manipulate heavy objects. The muscles in their arms work in much the same way as the human tongue.

Very Few Fossils

Scientists and zoologists use fossilized bones to learn about a species’ evolution. Lacking bones, the octopus presents a tricky situation. Though the task is difficult, it’s not impossible. Octopus fossils almost 100 million years old have been discovered that have eight legs with suckers and signs of ink.

Five Fun Facts About the Octopus

Did you know that octopuses have a total of nine brains? There is a central brain located between the eyes and eight additional “mini-brains” at the base of each tentacle. Although most creatures have one or two brains, octopuses have a total of nine brains and they put all of them to incredible use.

Furthermore: here are six fun facts you may not know about these cephalopods:

• Science has recorded around 300 different types of octopuses.
• All octopus species are venomous, as their saliva contains toxins that help subdue prey. However, only the blue-ringed octopus is known to be dangerous to humans.
• The largest member of the family is the Giant Pacific Octopus. The record is an octopus weighing over 600 pounds with an arm span of up to 30 feet.
• The octopus is exceptionally intelligent. They navigate mazes, solve problems, and make extravagant escapes from enclosures.
• The octopus can regenerate or regrow severed limbs.