TOP 10 ANIMALS THAT DON'T HAVE BONES - BIOLOGY - 2025

Some of the animals that do not have bones are the octopus, the crayfish, the sea anemones and the centipede. Animals that lack a backbone or an articulated skeleton are classified as invertebrate animals.

Invertebrate animals represent more than 90% of all species recorded by man.

Several of the invertebrates are often confused with vertebrate animals because they have a cartilage skeleton; but that skeleton, although it provides rigidity to the body, does not classify as bone.

The 10 most relevant invertebrate animals

1- Octopus

The octopus is an animal belonging to the group of mollusks. It is large in size, which can vary from 15 centimeters to 3 meters long.

The octopus is an omnivore; that is, it feeds on both animals and plants.

2- Squid

The squid, like the octopus, is a marine mollusk. Mollusks are soft-bodied invertebrate animals that are naked or protected by some type of shell.

The squid, also called teutid, can measure from 10 centimeters to 18 meters. The latter is the least common and is known as the giant squid.

3- Snail

The snail is a mollusk that has a spiral shell on its back, which covers it against any threat.

There are land and marine snails. Land snails can measure up to 12 inches in diameter, while the largest marine snails are barely half that - 6 inches.

4- Medusa

Jellyfish are animals more than 500 million years old. They have bodies with unique and varied characteristics.

They are animals that can be transparent and translucent, can present different colors and sizes, and are among the animals with the highest percentage of life expectancy.

5-

Centipedes belong to the class of chilopods and have different presentations. They can measure from less than a centimeter to around 30 centimeters.

They can be of different colors and some can secrete poison.

6-

The worm has an elongated and reddish body that can measure from very few centimeters to a maximum of 35 centimeters.

The earthworm feeds underground at night, and is recognized for its work benefits the development of some plants.

7- Crab

There are more than 4000 species of crabs; these have very varied sizes and colors.

All species have a very rigid body; however, the crab is an invertebrate because its skeleton consists of pure cartilage.

8- Planaria

This animal can be both marine and terrestrial. The planarian has a long, wide and flat body; hence the name.

This animal can have tentacles and a size that varies between one centimeter and 6 centimeters.

9- Sea urchins

Also recognized as echinoids, they are balloon-shaped animals that have movable spines, which can possess venom.

These animals come in different sizes, shapes and colors. Despite being static, some of the species are predators.

10- Sea anemones

Sea anemones are called this way because of their resemblance to the anemone flower. They are marine animals with a cylindrical body and tentacles at the top.

Many fish use anemones and their tentacles for larder and protection.

References

1. Editors of Encyclopaedia Britannica, "Invertebrata" in: Encyclopaedia Britannica (August 31, 2017) Retrieved: November 11, 2017 from Encyclopaedia Britannica: britannica.com.
2. Raskoff, K. "Jellyfish and Comb Jellies" in: Monterey Peninsula College. Retrieved on: November 11, 2017 from Ocean Portal: ocean.si.edu.
3. "Earthworm" in: National Geographic. Retrieved on: November 11, 2017 from National Geographic: nationalgeographic.com.
4. Editors of Encyclopaedia Britannica, "Planarian: Flatworm" in: Encyclopaedia Britannica (April 25, 2017) Retrieved: November 11, 2017 from Encyclopaedia Britannica: britannica.com.
5. D'Alessandro, M. "Cangrejo" (2017) in Animals. Retrieved on November 11, 2017 from Animals: animals.website.