In principle, rotifera exhibit a tripartite body plan, including the head region, the body and the foot.
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| ROTIFERA | ||
| About 1500 species, size between 40 and 2500 µm. | ||
| The nemathelminth class Rotatoria or Rotifera consists of microscopic, sessile or mobile animals. Rotifera are aquatic animals, but they are particular in choosing their habitate. Although many species live benthic or planktonic in lakes or in the sea (most species live in the fresh water), some species of the Digononta group live in mosses, lichens, strew, soil, tree holes or even in the gutter. Many species are cosmopolitans. As many other nemathelminthes, also most rotifera show a constant cell number, which is usually about 1000. For the species syncytially. |
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Body plan In principle, rotifera exhibit a tripartite body plan, including the head region, the body and the foot. BACK TO TOP |
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The rotary organ Appended on the head region, we can find the organ which gave the rotifera their name: the rotary organ or Corona. This organ, which is originally partitioned into a buccal field and a circoapical band, functions as a locomotive and feeding organ. The head also contains the dilobular cerebral ganglion which projects mainly into two ventrolateral nerve strains, which build up a foot ganglion. BACK TO TOP |
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Sensory organs Rotifera exhibit two or one eye, which is often made up as an ocellar neck-eye. The sensory eye-cells contain red pigment and show up lens-like inclusions. For many rotifera phototaxis is proven. Apart from the eye(s), rotifera exhibit sensory cells particularly at the corona, on the back, laterally and on the foot. BACK TO TOP |
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Digestive tract Only female individuals build up a complete digestive system. In males it is often reduced or even absent. It begins with the mouth leading into an elaborate pharynx with soft and hard appositions which build up a chewing stomach, the "mastax". From there, a narrow oesophagus leads into the resorbing parts. A sewer takes up excrements, excretes and gametes and releases it¥s content into the water through an anus. Excretion is carried out by a pair of protonephridia. BACK TO TOP |
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Respiration Rotifera have no respiratory and no circulative system. It is believed that gas is taken up through the ingested water and the spacious body cavity. BACK TO TOP |
This page last updated Oct 7th, 2004.