Biology subjects

Hape, E. E.

Publications and source records attributed to Hape, E. E..

4 recordsLinked to original sources

bioRxiv2026

How reliable is the use of ovarian dilatations for mosquito age-grading? A blinded multi-rater validation of the Polovodova method in Anopheles mosquitoes.

BackgroundAccurate estimation of mosquito age is critical for malaria surveillance, as only older female Anopheles mosquitoes can transmit the parasite. Traditional age-grading methods, include the Polovodova technique in which dilatations on the ovarian pedicel to tally completed gonotrophic cycles (GC) are counted. Despite their widespread use, these techniques remain poorly validated under realistic operational conditions, with limited evidence on their precision and accuracy across different parity rates, GC, and species. In this study, the accuracy and precision of the Polovodova method was evaluated across multiple age-graders and species under both laboratory and field conditions. MethodsA blinded validation study was conducted using laboratory-reared Anopheles arabiensis and Anopheles funestus (N > 3,600) spanning four gonotrophic cycles, and field-collected mosquitoes from Ulanga district, Tanzania (N = 600). Three blinded researchers performed dissections and readings, while a fourth unblinded researcher served as the reference reader (R0) to obtain ground truth (for parity) or assumed truth (for GC) for laboratory mosquitoes. Accuracy and precision for parity and gonotrophic cycle classification were assessed using pairwise inter-rater comparisons, percent agreement, Fleiss kappa and Cohens kappa O_SCPCAP(C_SCPCAPO_SCPLOWKC_SCPLOWO_SCPCAP)C_SCPCAP statistics. For field mosquitoes, which had no age-referenced group, only precision was assessed. FindingsThe Polovodova method accurately classified parity in both species, correctly identifying 98-100% of nulliparous and 94-96% of parous mosquitoes compared with the reference dataset. Inter-rater reliability for parity was almost perfect in An. arabiensis and An. funestus (k = 0.81-0.83), with 82-96% pairwise agreement. GC classification was highly accurate for early stages (GC0-GC2: 85-100%) but declined at later stages GC4(34-46%), reflecting systematic underestimation of mosquito age. Overall GC reliability was moderate (k = 0.56-0.59). Field classifications showed almost perfect agreement (k = 0.87-0.88), supporting operational applicability. ConclusionsThe Polovodova method provides robust estimates of parity and early gonotrophic-cycle status in Anopheles mosquitoes, but late-cycle classifications are more prone to reader disagreement and systematic underestimation. Operational use should therefore rely on trained multiple-reader workflows, including adjudication of discordant or late-cycle specimens, rather than single-reader classification. These findings provide empirical benchmarks for quality-assured Polovodova age-grading in malaria vector surveillance and intervention evaluation.

ecology↗

bioRxiv2025

Microsatellite Analysis of Genetic Differentiation Among Populations of the Malaria Vector, Anopheles funestus, across Mainland Tanzania Reveals Contrasted Patterns of Geographic Isolation and Gene Flow

BackgroundDespite Anopheles funestus s.s. being a highly competent and widespread malaria vector in Africa, its population structure remains largely understudied in many countries, including Tanzania. Herein, we examine the genetic diversity, geographic isolation, and gene flow of An. funestus populations across 10 administrative regions in mainland Tanzania. MethodsWe employed 12 previously used microsatellite DNA markers to describe genetic diversity, isolation by distance, and gene flow patterns among 10 An. funestus s.s. populations (n = 654) and one An. parensis population (n = 28), used as an outgroup, sampled across 10 regions in mainland Tanzania. ResultsOverall, allelic richness (Na) and genetic diversity (HS) did not differ significantly among populations. Although some loci and populations showed significant departures from Hardy-Weinberg equilibrium, the patterns were not indicative of sub-structuring within locations. Pairwise genetic divergence (FST) values indicated clear separation between An. parensis and An. funestus s.s., with values exceeding 0.2, consistent with species-level differentiation. Among An. funestus s.s. populations, the highest divergence was observed between southeastern coastal populations (Mtwara, Ruvuma, Lindi) and inland populations, with FST values up to 0.288. There was no evidence of isolation by distance. Instead, patterns of genetic divergence suggested connectivity across the Rift Valley and heterogeneity among southeastern populations. Neighbour-joining analysis and Bayesian genotype clustering identified three distinct population groups: (i) An. parensis (Dodoma), (ii) a genetically distinct An. funestus s.s. population from Mtwara, and (iii) a more homogeneous cluster comprising the remaining An. funestus s.s. populations. Notably, the Mtwara population appeared highly differentiated, with divergence approaching that between An. Funestus s.s. and An. parensis, supporting its distinctiveness but not undermining the role of An. parensis as an outgroup. ConclusionExcept for the Mtwara population, whose status will need to be clarified through whole genome sequencing, moderate genetic divergence was found among An. funestus s.s. populations across Tanzania, despite geographical separation and the Rift Valley. The observed genetic structure suggests that anthropogenic gene flow may play a key role in shaping population divergence. Future studies should aim to delineate the effects of local adaptation from recent gene flow to further explore these dynamics.

genetics↗

bioRxiv2025

Characterization of a new laboratory colony of Anopheles funestus mosquitoes established in Ifakara, Tanzania

BackgroundAnopheles funestus, a major vector of malaria in Africa, has proven difficult to colonize in laboratory settings, impeding research on its biology and control. After several attempts, our team recently succeeded in colonizing a strain of An. funestus from Tanzania (FUTAZ). The objective of this study was to analyse the key fitness and genotypic characteristics of these mosquitoes during multiple filial generations of laboratory adaptation and compare them to wild An. funestus from Tanzania and a pre-existing colony of An. funestus from Mozambique (FUMOZ). MethodsMeasures of mating success (percentage of female mosquitoes inseminated), body size (wing length), fecundity (number of eggs laid per female), and insecticide susceptibility (percentage of 24-hour mortality after exposure to insecticides) were compared between the newly established colonies of Tanzanian An. funestus (FUTAZ colonies), the long-established FUMOZ colonies, and a colony of Anopheles arabiensis maintained in the same laboratory. The maternal lineages of the An. funestus mosquitoes were investigated through a hydrolysis probe analysis of their mitochondrial DNA to identify distinct clades, I and II. Additionally, other intragenomic variations were examined through a PCR analysis of restriction fragment length polymorphisms (RFLP) on the third domain of 28S ribosomal DNA. These molecular markers were used to compare the FUTAZ colonies, FUMOZ colonies in Tanzania and South Africa, and the wild-collected An. funestus from Tanzania. ResultThe mating success and body size of FUTAZ females declined significantly from filial generations F1 to F6 relative to the founder population (F0), but then increased from F7 onwards eventually matching FUMOZ by F9. Fecundity was similar across all colonies tested. However, it took significantly longer for 50% of the females in the FUTAZ and FUMOZ colonies (over 10 days) to mate compared to females in the An. arabiensis colony (approximately 5 days). Insecticide resistance appeared to be lost during colonization, but this varied with insecticide classes. Majority of mosquitoes in the FUTAZ colony, as well as the wild-caught Tanzanian An. funestus belonged to Clade I (80.4-89.4%) and RFLP type "Y" (90.5-91.4%), while the FUMOZ colonies were mostly Clade II (65.5-88.5%) and RFLP type "MW" (90.5-91.5%). ConclusionThis study suggests that the mating success and body size of An. funestus decreases significantly during the early stages of colonization, then increase as the mosquitoes adapt to laboratory conditions. It is therefore crucial to have a large enough founder population to persist through these early generations in order to achieve stable colonization of An. funestus. The Clade and RFLP genotyping demonstrated the genetic similarities between the FUTAZ mosquitoes and wild-caught Tanzanian An. funestus, but also showed that the new colony can be distinguished from the FUMOZ colony.

ecology↗

bioRxiv2025

Delayed copulation and mating in the malaria vector Anopheles funestus compared to Anopheles arabiensis

Mating is a vital behavior for mosquito reproduction, yet it remains poorly understood under captive conditions. We examined the copulation dynamics of two key malaria vectors, Anopheles funestus, and Anopheles arabiensis, in controlled laboratory settings in Tanzania. We observed how variations in mosquito age and artificial lighting influence mating success for these two mosquito species within cages under controlled conditions. We conducted observations in 24-hour cycles, monitoring copulation events and insemination in females. We used generalized linear mixed models (GLMMs) for statistical analyses to assess how environmental conditions influence mating behavior. We found that Anopheles arabiensis exhibited rapid copulation, with 32.4% of individuals mating by Day 3 post-emergence, while An. funestus showed delayed activity, reaching a similar mating rate by Day 8. The introduction of artificial red light significantly accelerated copulation in An. funestus but did not affect An. arabiensis. Dissection confirmed successful sperm transfer and mating plug delivery in over 92% of copulating pairs for both species. Mating occurred primarily at night, with distinct peaks at 22:00 for An. arabiensis and 23:00 for An. funestus. In conclusion, our findings reveal species-specific differences in reproductive behavior, which could improve the colonization of An. funestus, a species historically challenging to rear in captivity. These insights may also inform the development of new vector control technologies, such as sterile insect techniques and genetic-based approaches, that exploit mosquito mating behaviors.

ecology↗