The growth ofTracheleuglypha dentata (Rhizopoda: Testacea) in clonal cultures under different trophic conditions

Twenty-four clones ofTracheleuglypha dentata were cultivated under different trophic conditions. Half were cultivated with soil extract which induced low bacterial growth. The other 12 were cultivated in the same medium with the addition of Cerophyl to enhance bacterial growth. The dynamics of each clone was followed for about 3 months by counting both live animals and empty shells. The rate of decomposition of empty shells was negligible. The number of empty shells are a direct measure for mortality. Parameters measured were densities, intrinsic rate of growth, generation time, production, and mortality. The densities increased in most of the clones until about the third week; it then reached a plateau or decreased slowly until the end of the experiment. After this initial period, the live animals closed their pseudostome with a thin membrane and remained quiescent until fresh food was given. The level of the plateau was significantly six times higher in the well-fed than in the starved clones, a difference due to a higher rate of growth induced by a shorter generation time during the first 10 days. This high growth produced giant shells, teratological forms created by the fusion of several shells. Mortality appeared at about the 20th day. Because it was higher in the well-fed clones than in the starved clones, it brought the densities of both clones to the same level after 3 months. The first empty shells were produced by either precocious mortality or abortion, as they did not contain reserve plates necessary for a new shell prior to reproduction. The mortality of adults came later and was probably linked with the age of the culture. The starved cells had an unusual morphology which disappeared when the medium was renewed.