perhaps the most well-known medusoid animals are the jellies (jellyfish). An example of the polyp form is Hydra spp. All cnidarians have two membrane layers, with a jelly-like mesoglea between them.Īnimals in this phylum display two distinct morphological body plans: polyp or “stalk” and medusa or “bell” (Figure 2). Cnidarians have two distinct body plans, the medusa (a) and the polyp (b). These coiled threads release toxins into the target and can often immobilize prey or scare away predators.įigure 2. When touched, the cells are known to fire coiled threads that can either penetrate the flesh of the prey or predators of cnidarians (see Figure 1) or ensnare it. The outer wall of the cell has hairlike projections called cnidocils, which are sensitive to touch. Nematocysts contain coiled threads that may bear barbs. These cells are present around the mouth and tentacles, and serve to immobilize prey with toxins contained within the cells. Nearly all (about 99 percent) cnidarians are marine species.Ĭnidarians contain specialized cells known as cnidocytes (“stinging cells”) containing organelles called nematocysts (stingers). Phylum Cnidaria includes animals that show radial or biradial symmetry and are diploblastic, that is, they develop from two embryonic layers. Identify the features of animals classified in class Hydrozoa.Identify the features of animals classified in class Cubozoa.Identify the features of animals classified in class Scyphozoa.Identify the features of animals classified in class Anthozoa. Identify common structural and organization characteristics of the phylum Cnidaria.
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