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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Echinosphaerium

  1. Echinosphaerium akamae (ref. ID; 3354)
  2. Echinosphaerium nucleofilum (Barrett, 1958) (ref. ID; 4080) reported year? (ref. ID; 4003)

Echinosphaerium akamae (ref. ID; 3354)

Descriptions

Large Heliozoon. (ref. ID; 3354)

Echinosphaerium nucleofilum (Barrett, 1958) (ref. ID; 4080) reported year? (ref. ID; 4003)

Descriptions

The trophic form of Echinosphaerium nucleofilum is multinucleated, but following paedogamy many uninucleated cysts be produced within a common gelatinous sheath. When viewed with the light microscope, the cysts are brownish and the encysted organisms are enclosed in a multilayered cyst wall. The outermost layer (layer 1) is the gelatinous material. Adjacent to this is an irregular and refractile layer (layer 2), separated by a broad space from a smooth homogenous layer lying next to the cell surface. The bulk of the cytoplasm of the encysted organisms is occupied by inclusions with refractile centers. Scanning electron microscopy of cysts stripped of their gelatinous coats reveals that layer 2 is composed of many spherical or otherwise rounded bodies with a porous appearance lying on an uneven membrane. (ref. ID; 4003)

Comments

The resting cysts of Echinosphaerium nucleofilum closely resembles that of Actinophrys sol in structure and elemental composition. Both organisms have cysts walls composed of seven or eight layers, the variable number being due to the presence of one or two inner granular layers. In Actinophrys, layer 2 takes the form of irregular siliceous plates and not the spherical structures visible in Echinosphaerium. However, the similar elemental composition indicates the homologous nature of the two types of structure. In both organisms, silicon is also present in the layer of helicoidally packed material. This layer in Actinophrys cysts contained iron that appears to be absent from the cysts of Echinosphaerium. This absence may not be of great significance, merely reflecting different trace amounts of this element in the medium. The nature of the organic layers of the cyst wall remains to be elucidated. (ref. ID; 4003)