Invertebrates

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles.

The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals.

A sponge is a primitive sedentary aquatic invertebrate with a soft porous body that is typically supported by a framework of fibers or calcareous or glassy spicules. Sponges draw in a current of water to extract nutrients and oxygen.

Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although the front pair of legs in some species has converted to a sensory function, while in other species, different appendages can grow large enough to take on the appearance of extra pairs of legs.

An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda, and include the insects, arachnids, and crustaceans.