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Figure 4.1a

Sea anemone body plan.

Longitudinal section and cross sections. After Barnes, 1980

The construction of anemones is accomplished with three tissue layers: an outer ectoderm, inner endoderm, and a mesogloea sandwiched in between. The three tissue layers are essentially laminar but highly folded to form the large surface of mesenteries that partition the coelenteron. The body plan is radially symetrical, though the radial symmetry of anthozoa is properly termed "bira-dial symmetry" because their mesenteries occur as couples on opposite sides of a plane bisecting the mouth, actinopharynx, and siphonoglyph(s). This bilateral symmetry is related to the hydrostatic design (Pantin, I960) and the need to ventilate the coelenteron, especially in large anemones (Hyman, 1940).

The mesenteries not only provide a large surface area for gas exchange, they are also an important site of digestion of food (see the topic feeding), and development of gametes (see topic reproduction). Descriptions of mesenteries often refer to them being "complete1' or "incomplete." If one imagines an anemone cut in cross section, the mesenteries form what looks like spokes, with the body wall that forms the column in the wheel position and the pharynx located at the hub. Complete mesenteries are attached to the column wall on one side and the wall of the pharynx on the other. Their presence provides structural support that facilitates the hydrostatic skeleton achieved by muscular contraction against the water filled cavities. Incomplete mesenteries are attached to the column wa 11 only, extending part of the way into the gastrovascular cavity, the lower part of the coelenteron below the pharynx, where prey items are digested. Mesenteries occur in "cycles" that are usually in multiples of twelve. The primary cycle

What Gastrodermis

Gastrodermis

Gastrodermis

Mesentery

Epidermis

Tentacles

Pharynx

Pharynx

Mesentery

Gastrovascular Cavity

Gastrodermis

Mesoglea

Mesentery

Epidermis

The COMPLETE guide to Aquariums

The COMPLETE guide to Aquariums

The word aquarium originates from the ancient Latin language, aqua meaning water and the suffix rium meaning place or building. Aquariums are beautiful and look good anywhere! Home aquariums are becoming more and more popular, it is a hobby that many people are flocking too and fish shops are on the rise. Fish are generally easy to keep although do they need quite a bit of attention. Puppies and kittens were the typical pet but now fish are becoming more and more frequent in house holds. In recent years fish shops have noticed a great increase in the rise of people wanting to purchase aquariums and fish, the boom has been great for local shops as the fish industry hasnt been such a great industry before now.

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Responses

  • alice
    What is gastrodermis?
    7 years ago

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