The trypanosomes of Ranidae. I. The effects of temperature and diurnal periodicity on the peripheral parasitaemia in the bullfrog (Rana catesbeiana Shaw)

Abstract

The peripheral parasitaemia of the Trypanosoma rotatorium complex in the bullfrog (Rana catesbeiana) is markedly affected by temperature. Over the long term, high temperatures are always coincident with high peripheral parasitaemia and vice versa; over the short term, increases in temperature bring about a corresponding increase in parasite level, and vice versa. A distinct diurnal cyclicity in parasitaemic level is found for one morph (type D) at elevated temperatures (26 °C); no such cyclicity was apparent at low temperatures (10 °C). Other morphs did not display any cyclicity at either temperature. It is proposed that the control of peripheral parasitaemia is due to changes in the level of metabolic activity of the host.Natural selection will favor any behavioral or growth pattern among trypanosomes which results in an increased peripheral parasitaemia at times and under conditions of optimal host–vector contact. The present results suggest an optimal host–vector contact for basking frogs. The possibility of an insect vector is discussed.