Table of Contents
What do all Cnidaria have in common?
All Cnidaria are aquatic, mostly marine, organisms. They all have tentacles with stinging cells called nematocysts that they use to capture food. Cnidarians only have two body layers, the ectoderm and endoderm, separated by a jelly-like layer called the mesoglea. Most Cnidarians have radial symmetry.
What is the same about all cnidarians?
All cnidarians have radial symmetrical. There are two major body forms among the Cnidaria – the polyp and the medusa. Sea anemones and corals have the polyp form, while jellyfish are typical medusae. When you look at them, you can see that these body forms are the same except that one is upside down.
What body part do all cnidarians have?
All cnidarians have two membrane layers in the body: the epidermis and the gastrodermis; between both layers they have the mesoglea, which is a connective layer. Cnidarians carry out extracellular digestion, where enzymes break down the food particles and cells lining the gastrovascular cavity absorb the nutrients.
Do cnidarians have neurons?
At the ultrastructural level, many cnidarian neurons have the combined characteristics of sensory, motor, inter- and neurosecretory neurons and thus appear to be multifunctional. We propose that these multifunctional neurons resemble the ancestors of the more specialized neurons that we find in higher animals today.
Do cnidarians have an endoskeleton or exoskeleton?
All cnidarians have hydrostatic skeletons, regardless of whether they also have mineralic and/or organic exoskeletons or endoskeletons. The muscles of the body wall operate against the fluid in the coelenteron to extend individual polyps and to effect the swimming of medusae, for example.
What type of skeleton does Cnidaria have?
Cnidarians have a hydrostatic skeleton. The contractile fibers act against the fluid-filled gastrovascular cavity. The movements are like a balloon; the animal can be short and thick or long and thin.
What kind of cells are found in cnidarians?
The more familiar polyp cnidarians include corals, hydras, and sea anemones. The tentacles of cnidarians have cnidocytes embedded within them. The cnidocytes of this jellyfish contain stinging nematocysts. Cnidocytes are specialized cells located in the epidermis of all cnidarians.
What are the physical characteristics of a cnidarian?
All cnidarians share several attributes, supporting the theory that they had a single origin. Variety and symmetry of body forms, varied coloration, and the sometimes complex life histories of cnidarians fascinate layperson and scientist alike.
Where are the muscles located in a cnidarian?
Muscles in cnidarians are extensions of the bases of ectodermal and endodermal cells. Individual muscle cells are relatively long and may occur in dense tracts in jellyfish or sea anemones. Most cnidarian muscles, however, are thin sheets at the base of ectodermal and endodermal layers.
How does a cnidarian stay in its polyp form?
When cnidarians are in the polyp form, they attach to a surface and remain stationary. Some cnidarians, such as hydra, stay in this polyp form their whole lives, while other organisms start in the polyp form and transform into the medusa body plan.