Voges, K. | bioRxiv Science

bioRxiv2025

Anopheles (Kerteszia) cruzii, the main malaria vector in the Brazilian Atlantic Forest, is a complex of at least five cryptic species

Malaria, a tropical disease caused by Plasmodium and transmitted by Anopheles, remains a public health concern in Brazil. While most cases occur in the Amazon, transmission persists in the Atlantic Forest, where Anopheles mosquitoes of the Kerteszia subgenus are the primary vectors of human and simian malaria. Previous studies using cytogenetics, isoenzymes, and molecular markers have suggested cryptic species within Anopheles (Kerteszia) cruzii and Anopheles (Kerteszia) bellator. We sequenced 55 genomes: 35 An. cruzii s.l. (four with Nanopore and 31 with Illumina), 12 An. bellator s.l., and eight An. homunculus, the latter two with Illumina. Phylogenomic analysis revealed at least five cryptic species within An. cruzii s.l., labelled A-E, with evidence of sympatry in some locations. Anopheles bellator s.l. also forms a species complex, comprising at least three distinct lineages. These cryptic species showed high genetic differentiation (FST range: 0.4-0.7), typical of interspecific comparisons. In contrast, An. homunculus populations showed low differentiation (FST [~] 0.2), suggesting a single widespread species. Our analysis confirms cryptic speciation in An. cruzii and An. bellator, but not in An. homunculus. These findings are important for understanding malaria transmission in the Atlantic Forest, given that vector competence may differ among cryptic species.

evolutionary biology↗

bioRxiv2025

Metabolic reprogramming and gut microbiota ecology drive divergent Plasmodium vivax infection outcomes in Anopheles darlingi

Anopheles darlingi is the principal malaria vector in the Amazon basin, where Plasmodium vivax accounts for the majority of cases. Despite its epidemiological importance, the molecular and microbial determinants of A. darlingi susceptibility to P. vivax remain poorly understood. Here, we investigated vector-parasite-microbiota interactions using experimental infections with field-derived P. vivax gametocytaemic blood, which produced two distinct infection phenotypes: low and high oocyst burdens. Transcriptomic profiling of mosquito midguts across key parasite developmental timepoints revealed that low-infection mosquitoes mounted an early and sustained response characterised by activation of detoxification pathways, redox regulation, aromatic amino acid catabolism, and purine depletion, likely coordinated through neurophysiological cues, which collectively create a metabolically restrictive environment for parasite development. These physiological changes were accompanied by reduced bacterial diversity and enrichment of Enterobacteriales and Pseudomonadales, taxa previously linked to anti-Plasmodium activity. Conversely, high-infection mosquitoes exhibited limited metabolic reprogramming, expansion of Flavobacteriales, and transcriptional signatures consistent with permissive physiological states, potentially associated with reproductive trade-offs. Importantly, low infection outcomes consistently arose from bloodmeals with the lowest gametocyte densities, suggesting that host- and parasite-derived components of the bloodmeal act as early conditioning factors that prime the mosquito midgut for either resistance or susceptibility. These findings reframe A. darlingi vector competence to P. vivax not as a fixed immune trait but as a dynamic outcome of early redox, metabolic, and microbial interactions. They also highlight ecological and physiological targets for transmission-blocking strategies and reinforce the importance of studying vector-parasite interactions in regionally relevant systems.

molecular biology↗