Meaning of Invertebrate Animals

What are invertebrate animals:

Invertebrate animals are those that lack a dorsal chord, backbone, and internal skeleton. That is, they have no 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 vertebrate 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 devoted himself to the study of invertebrate animals and classified them into 10 groups.

However, advances in zoology allowed a new reclassification to be made, which is what is currently used: arthropods, molluscs, porifera, cnidarians, echinoderms, platyhelminths, nematodes and annelids.

types of invertebrate animals


They are invertebrates characterized by the presence of an exoskeleton that sheds in the growth phase, articulated legs, segmented body in 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.

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Invertebrate animals, tarantula

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, octopus, squid and oysters are some representatives of this group.

Invertebrate animals, octopus

Octopuses are invertebrates of the mollusk group.


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

Marine sponges are poriferous invertebrates.

Invertebrate animals, sea sponges


They are marine invertebrates with a sac-shaped 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.

Invertebrate animals, corals

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 invertebrate echinoderms.

Invertebrate animals, starfish

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.

Invertebrate animals, flatworms

Prostheceraeus giesbrechtiia species of the flatworm group


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, causing a disease called hookworm.

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Invertebrate animals, nematodes

Eophasma jurasicuma type of invertebrate nematode.


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

Leeches and earthworms are two classes of annelids.

Invertebrate animals, annelids

Leeches are one of the most common annelid invertebrates.

see also

Vertebrate animals