Amazing Invertebrates

Invertebrates, or animals that have no backbone, are incredibly diverse, important, and fascinating. Invertebrates range greatly in size, with some that are smaller than a grain of salt and others can grow to half the length of a football field. Scientists estimate that invertebrates comprise 97% of all species on Earth and many are older than dinosaurs. Some of the earliest invertebrate fossils date back to 543 million years ago—a time when the entire state of Oklahoma was submerged by a sea known as the Western Interior Seaway. Today, you can appreciate (and touch) a variety of these prehistoric creatures in our Amazing Invertebrates exhibit. Here, you will find animals that digest food outside their bodies, animals that swim backwards, and animals with blue blood!


Arthropods are a group of animals that have an exoskeleton, jointed appendages (legs), and segmented body parts. Arthropods that have an exoskeleton, or hard protective covering, are called crustaceans. Since their exoskeleton is rigid, it must shed when the crustacean needs to grow. Crustaceans in this exhibit include: Ecuadorian white shrimp, giant freshwater prawn, lobsters, hermit crabs, and horseshoe crabs.


Given that cnidaria means “stinging cell,” it’s no surprise that all cnidarians have nematocytes, which are cells that sting. Some cnidarians use their nematocytes to catch prey, others use it as protection. Cnidarians in this exhibit include: corals, jellyfish, and tube anemones.


All mollusks are soft-bodied animals, but many of them receive protection from a hard shell.  Mollusks that have two shells connected by a hinge are called bivalves; this group of mollusks includes scallops, oysters, and mussels. Surprisingly, octopuses and squid are also classified as mollusks. They belong to a group of mollusks known as cephalopods. The word cephalopod literally means “head-feet,” since they all have a head attached to a set of tentacles. Mollusks in this exhibit include: red abalone, horse conch, and giant rock scallop.


The word echinoderm means “spiny skin.” Animals in this group are radially symmetric, which means they look the same around its center, unlike humans, who only look the same on the left and right (bilateral symmetry). Echinoderms in this exhibit include: sea stars and sea urchins.

Poriferans (Sea Sponges)

Sponges are one of the simplest and oldest life forms; they don’t have muscles or even a circulatory system, and they eat by cycling water in and out of their bodies. Types of sponges in this exhibit: red tree sponges and yellow and red ball sponges.

Fun Facts

  • Blue blood from horseshoe crabs is worth $15,000 per quart to the pharmaceutical industry.
  • Corals fluoresce! Though we can see a little bit of glow without any special tools, most of coral fluorescence is not visible to the unaided human eye. This is because most fish can see different wavelengths of light than humans can. Research done right here at the Oklahoma Aquarium shows that fluorescence in corals may be an indicator of stress that we can use to save coral reefs from bleaching and dying.
  • Jellyfish do not have brains but they do have nerve cells. Jellyfish nerve cells are spread throughout their bodies to form a network called a nerve net. Just like a brain, the nerve net allows jellyfish to take in information from their environment and respond.
  • Red abalone are eaten by sea otters and humans alike, but they are adept at avoiding smaller predators such as sea stars. They do so by twisting their shells or clinging to rocks.
  • Sea stars expel their stomachs into their prey, where they secrete digestive enzymes that liquefy the food for the stomach to absorb.
  • Fossils show sponges have existed for 650 million years, making them the oldest group of animals on Earth.
  • Shrimp respond to predators by rapidly flexing their tails, which causes them to jet backwards.

Touch Tanks

You can interact with horseshoe crabs, hermit crabs, chocolate chip sea stars, pencil urchins, and Ecuadorian white shrimp!

Written by Alyssa Rodriguez, February 2019.