Cnidarians
Classes of Cnidarians 1) Class: Anthozoa 2) Class: Hydrozoa CORALS, SEA ANEMONES 2) Class: Hydrozoa HYDROIDS, SIPHONOPHORES--Portugese Man-of-War 3) Class: Schyphozoa JELLYFISH
Anthozoans Anthozoans only exist in the polyp stage. Here are two types of this class: Corals The living materials are most often sponges, algae, and the corals themselves. Sea Anemones A sea anemone usually attaches itself to rocks or coral.
Hydrozoa The animals of the class hydrozoa have both a polyp and medusa stage. Siphonophores are a type of hydrozoan with a float for buoyancy. Probably the most famous of these is the species physalia, the Portugese-man-of-war, which is a type of colonial siphonophore.
Schyphozoans Jellyfish are cnidarians which lack the polyp stage of the life cycle. Therefore, they are always in the medusae stage. They are considered plankton because they cannot swim on their own--they are dependent upon the current to take them places. They are normally found in the epipelagic layer of the ocean.
Morphology Cnidarians are said to be the simplest organisms at the tissue grade of organization; their cells are organized into true tissues. Cnidarians are essentially bags made of two cell layers. The outer ectoderm, or epidermis, contains the cnidocysts, the stinging cells that are characteristic of the phylum. The inner endoderm, or gastrodermis, lines the gut, which in some cnidarians may be divided up by septa (as in the Anthozoa) or elaborated into branching canals (as in many Scyphozoa. In between epidermis and gastrodermis is the mesoglea, a layer of jellylike substance which contains scattered cells and collagen fibers. The mouth is often, but not always, surrounded by a ring of tentacles.
Short Video Clips All have radial symmetry All have stinging tentacles Can’t chase their food No brain Most are carnivores Drift, colonies, attached Nematocysts
Videos Cont. - 25% of all marine life lives in, on or around reefs -All have central body cavity Reefs are formed from polyps (dead & living) - Calcium Carbonate - Jet propulsion- helps jellyfish move - Bioluminescence- produce own light - Stinging cells paralyze/stun prey.
Videos Cont. Have squishy, soft body Body is more than 90% water Medusa= free floating stage
Videos Cont. Hollow gutted animals