Phylum Cnidaria
Phylum Cnidaria is the closest relative of Ctenophora. Of the 4 phyla we’ve talked about so far, Cnidaria is probably the most known phylum by common people. There are many different types of animals in Cnidaria, so common people use Cnidarians as the term whole when they are talking about the whole phylum. Cnidarians include coral, sea anemones, hydroids, and jellyfish. Cnidarians are rather simple animals, but they have more complex body features than sponges, because like all other phyla besides sponges, they have tissues, which make up important body parts. There are over 10,000 species of Cnidarians, which are divided into 6 phyla. Like Ctenophores, Cnidarians live in the ocean. Similarly to Ctenophores, their body is made of mesoglea. Cnidarians, along with Ctenophores, also have complex organs, such as muscles, nerves, and even organs that can sense. However, there are a few features that Ctenophores don’t have, which is what distinguishes cnidarians. Unlike other animals, Cnidarians have a special way of catching pray. When they are threatened or trying to capture prey, Cnidarians fire cnidocytes, which are explosive and contain toxin. Cnidarians very a lot in both size and shape. However, all Cnidarians have a few things in common. First of all they all have stinging cells which are usually located on tentacles. Those stinging cells are actually the cnidocytes. If you’ve been stung by a jellyfish at the beach, you have experienced they stinging cells. Just like the jellyfish hurt you when you got stung, it hurts prey even more because they are smaller. This is cnidarians’ ways of capturing prey. Second of all, most cnidarians have 2 stages. These are the medusa and polyp. Polyp is where the cnidarian is attached to a surface. Medusa is where the cnidarian is floating around freely. The way they go from medusa to polyp and from polyp to medusa varies. Some are born as one, and then go to another and stay there till they die. Some go back and forth from polyp and medusa. Coral actually only have a polyp stage. When they are born, they immediately attach themselves to the seafloor and stay there. That’s why when you think of coral, you think of them as a polyp. However, most people think of jellyfish as a medusa, when they are swimming freely. Cnidarians can reproduce sexually or asexually. As hermaphrodites, the sexual reproduction of cnidarians includes releasing egg and sperm and letting it reach another cnidarian of the same species. Asexual reproduction varies, but many cnidarians do this process by budding. That’s it for cnidarians, but no good book leaves out coral reefs. Coral reefs form when many coral polyps are together. When they die, their skeleton is left behind, which creates all the beautiful images we see of coral reefs, with all different shapes, from trees to brains to flowers.
Symmetry: Radial
Species Number: 9500+
Classification:
Kingdom Animalia
Eumetazoa
Radiata
Phylum Cnidaria
Class Anthozoa (corals, sea anemones, and sea pens)
Class Cubozoa (box jellyfish and sea wasps)
Class Hydrozoa (hydroids and hydras)
Class Myxosporea? (parasitic simple cnidarians)
Class Scyphozoa (true jellyfish)
Class Staurozoa (stalked jellyfish)
Heading Picture: Flower pot coral (Goniopora spp.)
Class Anthazoa (corals, sea anemones, and sea fans)
Order Scleractina (hard corals)
Family Poritidae (reef-building hard corals)
Genus Goniopora (flowerpot corals)
Species G. albiconus, G. burgosi, G. columna, G. planulata, G. polyformis, G. tenuidens (flower pot corals)
Symmetry: Radial
Species Number: 9500+
Classification:
Kingdom Animalia
Eumetazoa
Radiata
Phylum Cnidaria
Class Anthozoa (corals, sea anemones, and sea pens)
Class Cubozoa (box jellyfish and sea wasps)
Class Hydrozoa (hydroids and hydras)
Class Myxosporea? (parasitic simple cnidarians)
Class Scyphozoa (true jellyfish)
Class Staurozoa (stalked jellyfish)
Heading Picture: Flower pot coral (Goniopora spp.)
Class Anthazoa (corals, sea anemones, and sea fans)
Order Scleractina (hard corals)
Family Poritidae (reef-building hard corals)
Genus Goniopora (flowerpot corals)
Species G. albiconus, G. burgosi, G. columna, G. planulata, G. polyformis, G. tenuidens (flower pot corals)