Invertebrates are the animals in our world without a backbone. You know a lot of them. The insects and crustaceans have outer skeletons, while the mollusks and the worms don’t have much of a skeleton. Invertebrates make up more than 90% of the animals on earth and are part of the base of our food chain.
Corals, sponges, and worms are common words to our ears, but scientists would call them cnidarians, poriferans, and annelids. They each have their own phylum and each phylum is extremely diverse. One thing they all have in common is that they are ancient and simple biological organisms.
Corals, Anemones, & Jellies
Phylum Cnideria contains corals, anemones, and jellyfish. Their name comes from the Greek word cnidos which means stinging nettles. Most animals in this phylum have a capability to sting prey with nematocyst cells which either sting or inject a toxin. Corals are in class Anthozoa and are sessile polyps that live in colonies which act as a single organism. The shapes of corals can be incredibly diverse, but they are all groups of tentacled creatures that live on a calcareous skeleton and share nutrients. Most corals are known for being very colorful, but they don’t actually have color. Many live symbiotically with algae that are extremely colorful. The algae provide carbohydrates to the corals, while the corals provide carbon dioxide for the algae. Sometimes, the coral may become stressed and it can eject the algae, which is known as “coral bleaching”. Coral is well known for the reefs it can form with its calciferous skeleton, but in central California, coral doesn’t form reefs. But, like a coral reef, corals of Point Reyes are extremely sensitive to change in salinity and temperature. Development along coastal areas can result in runoff, which changes the salinity of the water and can kill the corals.
Phylum Porifera encompasses the sponges of the sea. The skeletons of sea sponges are well known because they are natural sponges and are often sold with spa products. There are different types and not all of them are useful as soft sponges because many varieties have skeletons that are hard and spiky. Sponges are extremely simple creatures and do not have blood or organs. They live by absorbing all of their gasses and nutrients from the water and returning wastes to the water by direct diffusion through cell walls. Most species require a solid rock to spend their life on, so it is not uncommon to see a bunch of corals growing together on an ideal spot which is referred to as a “sponge garden”. Sponges can be found in intertidal zones and in the deep sea.