Daily periodicity in the diverse activities of parasites occurs across a broad taxonomic range. The rhythms exhibited by parasites are thought to be adaptations that allow parasites to cope with, or exploit, the consequences of host activities that follow daily rhythms. Malaria (Plasmodium) parasites are well-known for their synchronised cycles of replication within host red blood cells. Whilst most species of Plasmodium appear sensitive to the timing of the daily rhythms of hosts, and even vectors, some species present no detectable rhythms in blood-stage replication. Why the intraerythrocytic development cycle (IDC) of, for example P. chabaudi, is governed by host rhythms, yet seems completely independent of host rhythms in P. berghei, another rodent malaria species is mysterious. This study reports a series of five experiments probing the relationships between the asynchronous IDC schedule of P. berghei and the rhythms of hosts and vectors by manipulating host time-of-day, photoperiod and feeding rhythms. The results reveal that: (i) a lack coordination between host and parasite rhythms does not impose appreciable fitness costs on P. berghei; (ii) P. berghei’s IDC schedule is impervious to host rhythms, including altered photoperiod and host-feeding-related rhythms; (iii) there is weak evidence for daily rhythms in the density and activities of transmission stages; but (iv), these rhythms have little consequence for successful transmission to mosquitoes. Overall, host rhythms do not affect the performance of P. berghei and its asynchronous IDC is resistant to the scheduling forces that underpin synchronous replication in closely related parasites. This suggests that natural variation in the IDC schedule across species represents different parasite strategies that maximize fitness. Thus, subtle differences in the ecological interactions between parasites and their hosts/vectors may select for the evolution of very different IDC schedules.
O'Donnell, Aidan; Reece, Sarah. (2021). The ecology of asynchronous asexual replication: Plasmodium berghei’s intraerythrocytic development cycle is resistant to host rhythms, [dataset]. University of Edinburgh. School of Biological Sciences. https://doi.org/10.7488/ds/2984.