THE 27 MOST INCREDIBLE MARINE INVERTEBRATE ANIMALS - BIOLOGY - 2025

The animals marine invertebrates are characterized by having no backbone, but may have a non outer skeleton bone, called the exoskeleton.

There are different types of invertebrates: porifers, cnidarians, annelids, arthropods, mollusks and echinoderms. These are the types of marine invertebrates:

• Poriferous and cnidarians are the simplest organisms. They live in aquatic environments and have radial symmetry (radial shape) or lack shape.
• The marine annelids or polychaetes are hairy worms and their bodies are made up of rings.
• Aquatic arthropods or crustaceans have a segmented body and a very hard exoskeleton. Mollusks are both terrestrial and marine. They are characterized by having a muscular body, a calcareous shell and a radula, which is the organ they use to feed themselves.
• Echinoderms are all complex marine animals, whose bodies are covered in a shell made up of calcareous plates and thorns, such as starfish.

Top 27 marine invertebrate animals

1- Tomato anemone

If you have a fish tank at home, you must have a tomato anemone. Also called actinia, it is a species that looks like a fungus with tentacles.

Actinias can contract or extend their tentacles, allowing them to hunt small fish for food. Anemones reproduce by division and can live in waters with different temperatures and lighting. Anemones fixate on rocks.

2- Starfish

The protagonists of selfies on the beach! Yes, these animals are the most popular and loved invertebrates by all. What many do not know is that the stars die asphyxiated when being taken out of the water, at the moment in which we photograph ourselves with them because they do not breathe air, but water.

These animals usually have 5 or more arms. If you cut a starfish in half, it will regenerate and survive by turning into two.

3- Corals

Corals are invertebrate colonial animals that belong to the cnidaria class. They feed on plankton and small fish that they catch with their tentacles. They require sunlight to reproduce and live in shallow waters.

Coral reefs are popular spots for scuba divers, as small fish nest among them. The Great Barrier Reef, off the Australian coast, is the largest reef in the world. The second largest Coral reef is in the Caribbean Sea.

4- Bovagant

Lobster is a crustacean similar to lobster, reaching up to 70 centimeters in length. It has 5 pairs of legs, four of which are small. The last pair, much larger, serves to defend him. They are highly valued as part of the gastronomy of many countries.

5- Lobsters

The palinurids or lobsters are another class of crustacean that is highly appreciated in gastronomy. There are different types that differ in the size of their tweezers. For example, the Juan Fernández lobster is far from the European spiny lobster.

The latter lives in the Mediterranean Sea and its fishing is the economic base of towns, such as Menorca, where a typical lobster-based dish has become famous, called Caldereta de Langosta. Delicious!

6- Herreña lobster

The black lobster or brown lobster is an endangered species that lives in the Atlantic Islands. This brown marine crustacean can measure up to 37 centimeters.

7- Jellyfish

Jellyfish or sea tears are beautiful translucent marine animals that have a bell shape and a jelly-like body. Some jellyfish are bioluminescent and glow in the dark. They use their tentacles to catch their prey and defend themselves from their attackers.

Some are toxic and their stings cause a burning sensation in victims, but some fish are immune and therefore lurk among the jellyfish to defend themselves against their attackers.

The most poisonous jellyfish in the world is the sea wasp, which lives in Australian waters. Its venom can cause cardiac arrest in humans since it automatically enters the blood.

8- Sea sponges

Sea sponges are interesting animals, which were considered plants until 1765 when it was discovered that their digestion was intracellular and that they filter the water, since they feed on the organisms that are in it.

These animals are considered to have existed since the Precambrian period. The sponge has a cellular organization and lacks tissues, since its cells are totipotent, that is, they can adopt different functions, which allows them to be autonomous. Sponges are the only animals that lack a nervous system.

9- Sea cucumbers

Sea cucumbers are vermiform invertebrates, that is, they look like worms. Although they are distinguished by their pullas or holothurians. It has a mouth and an anal opening. Its mouth is surrounded by tentacles.

In some Asian countries and in Spain, dishes are prepared based on these animals, such as trepang in China or espardeña in Spain.

10- Sea apples

Sea apples are a type of round sea cucumber. They can be up to 20 cm long, filter water and others when faced with danger can expel their internal organs to entertain predators and escape. Then their organs regenerate.

Although this species is also a sea cucumber, it is not advisable to keep them in fish tanks since their toxins can poison the other inhabitants of them. The yellow sea cucumber also releases these types of toxins.

11- Hermit Crab

The hermit or paguro crab is a crustacean that lives in conch shells to cover its abdomen and protect itself from danger.

There are approximately 500 species in the world and some of them are terrestrial. This crab is the main ingredient in several typical dishes from Spain, especially from the Balearic Islands.

12- Artemia salina

The brine shrimp is an almost translucent cosmopolitan crustacean that can also live in fish tanks. Due to its nutritional properties, it is frequently used in aquariums (raising fish in aquariums).

An interesting fact is that the eggs of this animal can be preserved for up to 10 years in a metabolically inactive state and then, under more favorable climatic conditions, the egg can be activated again.

13- Prawn

The shrimp or northern cleaner is an omnivorous shrimp, that is, it feeds on plants and animals. Their diet is based on plankton, dead tissues, and parasites.

This little animal is a friend of coral reefs and other larger sick fish, since they are responsible for cleaning impure surfaces and also filter the water.

14- Sea lilies

Sea lilies or feathered stars are echinoderms that have the appearance of a plant. They are considered to have inhabited the earth since the Paleozoic and there are more than 600 species. They filter water and feed on zooplankton. They come in different colors and sizes.

15- Casseroles

Sea pans have been on earth for 300 million years. Their tough exoskeleton has allowed them to survive predators. Under its shell hides a little animal very similar to the spider, only with one more leg.

An interesting fact about these animals is that their blood reacts to bacterial endotoxins. For this reason, scientists have developed a test to determine possible infections based on your blood.

Due to the speed of the reaction, this test is used in astronauts and in people exposed to dangerous materials that can be toxic to humans.

16- Swiss cow

The Swiss vaquita is a species of gastropod mollusk that lives in the Mediterranean Sea and the Atlantic Ocean. It has no shell and is characterized by its peculiar coloring: it is white with freckles. It has between 6 and 9 main gills and secondary gills around the anus.

17- Sea Dragon

The sea dragon is a hermaphroditic sea slug, which looks like a mythological animal. It belongs to the Glaucidae family and is considered a unique species. Its body is a flat trunk with 6 branches, its teeth look like swords.

This cosmopolitan species can live in cold and warm waters. Scientists argue about the possibility that this animal cannot swim, but is dragged by the current.

This animal can be poisonous, since it feeds on other poisonous animals and being immune to its venom, its bite can pass this poison to another species. Its color serves as camouflage.

18- Fiddler Crab

The fiddler crab or skipjack is a crab whose main characteristic is its claws or clamps, which have different sizes, one of them being very large. This large pincer is called a “violin claw”.

There are 94 species of fiddler crabs. These crabs fight each other to impress the females. The violin claw is not always considered to be the strongest grip and its large size is a way to impress and scare your enemies.

19- Octopuses

Octopods or octopuses are omnivorous marine animals, which have 8 arms. These have sticky suction cups that stick to different surfaces. They also have 3 hearts and their brain is highly developed.

Octopus blood is blue due to the high level of iron it has. The third right arm of the male octopus is its sexual organ, which is used to fertilize the female. Octopuses are shy and are the most intelligent invertebrates.

There are different types of octopus, some dangerous and some not. For example, blue-ringed octopuses are poisonous.

20- Squid

There are several species of squid. These mollusks get their name from the calcareous bone on their head, known as the feather or reed. They also have 3 hearts. Thanks to chromatophores, special cells in their skin, squid can change color.

When I feel in danger, squid spurt ink. These animals expel water under pressure, which allows them to move.

21- Fabiana

The fabiana or bigeye octopus of red or orange color with white fluorescent spots. Unlike other octopuses, it is more curious and comes into contact with people who dive, if they do not behave in a threatening way. They inhabit East Africa, the Mediterranean and Red Seas.

22- Umbraculum umbraculum

The umbraculum umbraculum is a species of mollusk that inhabits the crevices of the rocks or stays under the sand. It can inhabit up to 100 meters deep. New Zealand is where there is the largest reserve of this invertebrate.

23- Chocos

The cuttlefish or cuttlefish are cephalopod mollusks that are distinguished by their color. Chromatophores in their skin allow them to camouflage themselves and manipulate light to send messages to their friends and warn them of predators in case of danger.

Cuttlefish can manipulate their color to take on the color of different surfaces, they can leave traces of color, which disorient predators and make them believe that cuttlefish are larger.

Their eyes are special in that they pick up on the polarization of light and can look forward and backward at the same time. It also has 3 hearts and its blood is blue-green due to the copper it contains.

24- Shrimp

Shrimp are decapod crustaceans, that is to say 10 legs, freshwater, much smaller than prawns and prawns. There are river species and others from tropical waters. There are more than 2,500 types of shrimp.

We can find them in different sizes, from 2 to 37 millimeters. For example, the dancing shrimp lives in subtidal areas and is a very shy animal that stays hidden during the day. It moves in large groups and feeds on carrion, small invertebrates and organic matter.

25- Prawns

Prawns or lancostadae are decapod crustaceans of the suborder dendrobranchiata, which inhabit all the seas of the world. Its length varies from 12 to 15 centimeters. They live in different depths.

26- Nautilins

Nautilins are one of the oldest species and are considered true living fossils. Your species has survived for millions of years and has not undergone major changes.

These animals have a prominent hair and many tentacles. Moves when using jet propulsion. This animal can survive in conditions of lack of oxygen, since it is able to regulate its heart rate.

27- Sea shells

Sea shells are marine mollusks, whose main characteristic is their shell. Many of them can survive in water and on land. The shells are made of calcium and are shaped like a spiral.

There are approximately 75,000 species. Their shell gives them an advantage against predators to defend themselves. They inhabit all fresh and salt water environments.