Studies on aging in a bdelloid rotifer. I. The effect of various culture systems on longevity and fecundity

Techniques are described for the aseptic manifpulation of rotifers cultured in exposed containers. The elimination of bacterial contaminants resulted in much greater stability of mean life span than had been obtained from contaminated (synxenic) cultures. The aseptic procedures have also facilitated the development of a mass culture system which provides milligram quantities of animals of known ages. Comparisons of dry weight and enzymatic activities of animals grown in mass and isolation cultures have demonstrated unifromity of animals maintained in the two systems. A number of bacteria and algae were tested as food sources. Optimal reproductive rate and longevity were obtained when a mixture of Aerobacter aerogenes and a strain of Pseudomonas species designated N6 was used (a dixenic culture system). Mortality among dixenically cultured rotifers was low until after reproduction ended. The reproductive rate was reduced when the animals were grown monoxenically on either A. aerogenes, Chlorella vulgaris or Chlamydomonas reinhardi. A second species of Pseudomonas reduced longevity without any effect on reproduction. Dry weight of the rotifers increased throughout the entire life span, and fat, ash and protein content increased in proportion to the dry weight. RNA content remained constant. Both total and specific activity of lactate and malate dehydrogenase decreased in older animals. These patterns of enzyme activity are similar to those found in other organisms.