The Cultural Forms of Trypanosoma ranarum (Lankester, 1871). I. Relation Between Cyclic Development of Culture Forms, Oxygen Consumption in the Presence of Glucose, and Malonate Inhibition.*

SYNOPSIS. Ten‐ or 12‐day cultures of Trypanosoma ranarum in Diamond's SNB‐9 medium contain large numbers of slender crithidia and considerably smaller numbers of pear‐shaped crithidia, but in fresh media the pear‐shaped bodies constitute about 93% of the population after 5 days whereas slender forms make up about 4–5%; the remainder are leishman bodies. Succeeding days show a different cycle in that the slender forms increase to some 93% at 10–13 days and the pear bodies decrease to some 3% of the total at the same time. When washed in Krebs‐Ringer phosphate buffer alone, neither morphological type shows endogenous respiration; in glucose containing buffer, O2 consumption becomes evident; pear‐shaped crithidia use, on an average, 12.6 μl O2/hr/108 whereas slender forms utilize 17.7 μl O2/hr/108 parasites. Malonate at 0.01 m inhibits O2 consumption of slender forms about 61% as compared to 27% with the pear‐shaped bodies. A speculative discussion of the relation between morphological types, O2 consumption in the presence of glucose, and malonate inhibition is presented.