Invertebrate Characteristics
Invertebrate animals are all those members of the Metazoan or Animalia kingdom that are not included within the vertebrate subphylum of the chordate phylum. They receive this name due to the absence of a vertebral column or notochord and an articulated internal skeleton.
95% of animal species are invertebrates, so it is a very diverse group that includes animals with very different structures that are included in different phyla (Phylum), type or trunk.
Invertebrates are ectotherms, so they cannot keep their body temperature constant, but instead have that of the environment in which they live.
The most important groups of invertebrate animals are the following:
- Poriferous: they have the body perforated by a system of pores and channels through which water circulates. For example, sponges.
- Cnidarians or coelenterates: they have a gastric cavity that communicates with the outside through a single opening. Its symmetry is radial, such as polyps and jellyfish.
- Annelids: they have an elongated and cylindrical body divided into rings. For example, earthworms , leeches.
- Molluscs: they have a soft body that may or may not be covered (by one or two shells). For example, clams, squid, octopus, snails.
- Arthropods: they present an exoskeleton, they have a segmented body and articulated legs. For example, arachnids, insects, myriapods, crustaceans.
- Echinoderms: they have a calcareous exoskeleton, radial symmetry, and an ambulacral apparatus that allows them to move. Some species have spines. For example, sea urchins and starfish.
