Anopheles mosquitoes are associated with diverse microorganisms that could have important impacts on host biology and vectoral capacity. Eukaryotic symbionts such as fungi have been isolated from Anopheles. Whether they are stably associated and transstadially transmitted across mosquito life history or to their subsequent generation and their fitness cost thereof remains largely unexplored. There is need to find anopheline fungal symbionts that can be maintained across life stages or vertically transmitted, otherwise just conferring protection without intimate co-existence may limit their sustainable utilization.  Here, we show that Leptosphaerulina sp. fungus isolated from the midgut of Anopheles gambiae possess a stable relationship with the host. The fungus imposes minimal fitness cost when re-introduced through co-feeding and is transstadially transmitted across developmental stages and to their subsequent progeny, and is present in field larvae and adult mosquitoes at moderate levels across geographical regions. We observe that induction of host immunity was necessary for its establishment and persistence in Anopheles gambiae. These traits were attributed to systemic infection of the midgut and reproductive tissues. We anticipate that this isolate could be exploited in paratransgenesis.

Fungus was isolated from dissected mosquito guts and reintroduced through co-feeding; presence and densities were determined by culture and high resolution melting (HRM-qPCR) Aassay. sequencing and resequencing were used to confirm isolates in developmental stages and their offspring.