Meaning of invertebrate animals

What are invertebrate animals:

Invertebrate animals are those that lack a dorsal cord, vertebral column, and internal skeleton. I mean, they don't have bones. They are generally small in size and have some type of protective structure or exoskeleton, such as shells.

According to taxonomic classifications, invertebrates are all those animals that do not fall within the vertebrates subphylum, which in turn belongs to the chordate phylum of the animal kingdom.

Approximately 95% of the living species known to date belong to this group, which is why they represent the greatest biodiversity on the planet.

Due to their small size and in many cases, difficult location, the study of invertebrates was relegated for centuries. It was only in the 18th century that its potential in terms of scientific research began to be considered, mainly due to the interest of the French naturalist Jean-Baptiste Lamark, who dedicated himself to the study of invertebrate animals and classified them into 10 groups.

However, advances in zoology made it possible to make a new reclassification that is the one currently used: arthropods, mollusks, porifers, cnidarians, echinoderms, flatworms, nematodes and annelids.

Types of invertebrate animals


They are invertebrates characterized by the presence of an exoskeleton that molts in the growth phase, articulated legs, a body segmented into two or three regions, with repetitive patterns.

Arachnids (mites, scorpions, and spiders), insects (ants, butterflies), myriapods (such as centipedes), and crustaceans (crabs, prawns, prawns) belong to this group.

Spiders are invertebrate animals of the arthropod group.


They have a soft body, in some cases protected by a shell. Their bodies are symmetrical and without segmentation.

Clams, octopuses, squid and oysters are some representatives of this group.

Octopuses are invertebrates from the group of mollusks.


A group of generally aquatic and sac-shaped invertebrates belongs to this category. Water leaves your body through a large opening at the top called the “osculum” and enters through smaller pores located in the walls of your body.

Marine sponges are poriferous invertebrates.


They are marine invertebrates with a sac-like body and have a single opening that serves as a mouth and anus at the same time and usually has one or more tentacles.

Jellyfish, corals, and polyps are cnidarian invertebrates.

Corals are a type of cnidarian invertebrate.


They are marine invertebrates with pentaradial symmetry; this means that they have 5 regions around a central disk. They have an exoskeleton made up of limestone plates that, in some cases, may have spikes.

The stars and sea urchins represent the group of echinoderms invertebrates.

A starfish, belonging to the group of echinoderms.


Also known as flatworms, they are the simplest animals with interneurons. Most are hermaphrodites and have parasitic life forms, requiring one or more hosts during their life cycle.

Parasites such as tapeworms are the best known species of flatworms.

Prostheceraeus giesbrechtii, a species of the group of flatworms


Also known as cylindrical or round worms, these invertebrates are characterized by having a body without segmentation, with muscles that allow their movement. Some nematodes are transmitting agents of intestinal diseases.

The Necator americanus It is an intestinal parasite, from the group of nematodes, which causes a disease called hookworm.

Eophasma jurasicum, a type of invertebrate nematode.


They are invertebrates with the body segmented into rings and with metameria, that is, certain organs are repeated in each ring.

Leeches and earthworms are two kinds of annelids.

Leeches are one of the most common annelid invertebrates.

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