Assessment of the developmental success of Anopheles coluzzii larvae under different nutrient regimes: effects of diet quality, food amount and larval density

Abstract

BackgroundIn a context of increasing resistance of both vectors toward main classes of insecticides used in public health and parasites toward anti-malarial drugs, development of new and complementary molecules or control approaches is fundamental to achieve the objective of controlling or even eliminating malaria. Concerning vector control, the sterile insect technique and other genetic control approaches are among promising complementary tools in an integrated management strategy for malaria control. These approaches rely not only on a good understanding of vector biology (especially during larval stages), but also on the availability of adequate supplies and protocols for efficient mosquito rearing. The aim of this study was to assess the factors impacting the life history of Anopheles coluzzii mosquitoes at the larval stage, in the context of genetic and sterile insect approaches to control malaria vectors.MethodsThe effect of different larval diets and larval rearing densities on the development of An. coluzzii were evaluated in the laboratory. Emergence rate (ER), pre-imaginal developmental time (DT) and adult wing length (WL) were measured under different food regimes. Four diets were tested among which three were provided by the Insect Pest Control Laboratory (IPCL) of the FAO/IAEA Joint division.ResultsData showed significant differences in the quality of the different diets and suggested a negative density dependence in all three life history parameters measured under tested rearing conditions. ER and WL increased with food availability, but decreased with increasing larval density. Conversely DT was shortened with increasing food availability but increased with larval density. These data demonstrates intraspecific larval competition modulated by food amount and space availability. Of the four diets tested, the one made of a mix of tuna meal, bovine liver powder, brewer’s yeast, squid liver powder and vitamin mix (diet 2) yielded the best results as it produced a good balance between ER, DT and WL. Food availability for optimal development (highest survival at shortest time) was in the range of 180–400 µg/larvae/day for the three diets provided by the IPCL.ConclusionThere is an interaction between diet type, diet concentration and larval density. Best results in terms of optimal larvae development parameters happen when moderately high values of those three variables are observed.

Toward implementation of combined incompatible and sterile insect techniques for mosquito control: Optimized chilling conditions for handling Aedes albopictus male adults prior to release

“…The combined IIT-SIT strategy involves several steps including mosquito mass rearing, sex separation, irradiation, packing, transportation, release and monitoring. Progress has been achieved on mosquito mass rearing by developing standard operation procedures (SOPs) for egg handling (quantification, hatching and storage) [15][16][17][18], larval rearing (larval diet, rearing density, rearing conditions and rack system) [19][20][21][22][23][24][25][26][27] and adult rearing (rearing density, blood-feeding and cages) [28][29][30], respectively. The importance of sex separation for mosquito IIT-SIT is self-evident, and despite efforts and progress being made, there is still a lack of available genetic sexing strains for Aedes spp.…”

Improvement of Water Quality for Mass Anopheline Rearing: Evaluation of the Impact of Ammonia-capturing Zeolite on Larval Development and Adult Phenotypic Quality

“…Here, starvation resulting from intra-instar competition may have accounted for the reduced survival in trays with 400 larvae [40,41]. Larval overcrowding is relatively common in insectaries due to lack of space and/or standardized rearing protocols, leading to suboptimal emergence rates and phenotypic quality [39,42]. Our results suggest that zeolite might potentially allow for rearing at higher larval densities but would require higher doses of zeolites.…”

“…A second but not exclusive explanation for the lack of impact of zeolite at higher density may be that the bene ts from ammonia reduction were obscured by intra-speci c competition both for food and space [39]. Here, starvation resulting from intra-instar competition may have accounted for the reduced survival in trays with 400 larvae [40,41].…”

“…This allowance for synchronous hatching and pupation with the use of zeolite is the ideal condition both for smaller insectaries and mass-rearing facilities [43]. Any additive that can shorten preimaginal development time is welcome as it will reduce labour costs and enhance accelerated production of adults [39]. This is particularly desirable in the mass rearing of adult mosquitoes for vector control/research programmes where e cient rearing systems which balance larval density, nutrition and water quality are needed [39,44].…”

Improvement of water quality for mass anopheline rearing: Evaluation of the impact of ammonia-capturing zeolite on larval development and adult phenotypic quality

“…A second but not exclusive explanation for the lack of zeolite's impact at higher density may be that ammonia reduction bene ts were obscured by intra-speci c competition for food and space [36]. Here, starvation resulting from intra-instar competition may have accounted for the reduced survival in trays with 400 larvae [37,38].…”