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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4766

Colin G. Ogden; The Agglutinate Shell of Heleopera petricola (Protozoa, Rhizopoda), Factors Affecting its Structure and Composition. Arch.Protistenk 137:9-24, 1989

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Shell architecture exhibited by most species of testate amoebae shows considerable diversity depending on the material used in construction. In nature, species of Heleopera are unique in building a shell composed of almost equal parts of shell plates and extraneous mineral grains. These species do not secrete their own shell plates but derive them by predation from the cytoplasm of smaller testate amoebae, where they are stored as reserve plates prior to division. Studies of H. petricola in culture demonstrate that this species can construct a shell completely of predated plates in the presence of prey animals alone, but will revert to its usual pattern when mineral grains are added to the culture medium. In the absence of mineral grains, the animal will use either broken portions of empty shells, or ground glass-wool particles in roughly equal proportions with shell plates. Six smaller siliceous testate amoebae, of the family Euglyphidae, have been successfully used as prey species, serving for both food and a source of shell building material. The requirement of predated plates needed in shell construction by Heleopera may be one reason for the long doubling times, 10-14 days, determined from cultures. The presence or absence of mineral particles has no significant effect upon the doubling time of H. petricola cultures fed with the small prey species. However, differences in the doubling times were detected for cultures feeding upon different prey species, which may be related to prey plate size, with the smaller plated species giving the longer doubling time.