Effect of larval diets on the life table parameters of dengue mosquito, Aedes aegypti (L.) (Diptera: Culicidae) using age-stage two sex life table theory

The current study regarding the effects of larval diets on the life table parameters of dengue mosquitoes, Aedes aegypti was conducted under laboratory conditions at 27 ± 2 °C and 60 ± 5% relative humidity at NIFA (Nuclear Institute for Food and Agriculture) Peshawar, Pakistan. The data on life table parameters of Ae. aegypti reared on Diet 1 (replacement diet), Diet 2 (Khan's diet for Anopheles), Diet 3 (Khan's modified diet) and Diet 4 (IAEA diet) were analyzed using the age-stage, two-sex life table software. Diet 4 (IAEA) was used as a control for comparison. The results indicated that significantly maximum percentage of egg hatching of Ae. aegypti was observed when reared on Diet 4 (73.86%) and Diet 3 (72.90%), while less % of egg hatching was recorded in Diet 1 (40.67%) and Diet 2 (55.53%). The data further showed that the Diet 3 had a highest intrinsic rate of increase (r) (0.097 ± 5.68 day^-1), finite rate of increase (λ) (1.10 ± 6.26 day^-1) and net reproductive rate (R₀) (11.99 ± 1.52 eggs/female) followed by Diet 2 and Diet 4. The mean generation time (T) of Ae. aegypti reared on Diet 3 (23.67 ± 0.86 days) and Diet 1 (24.05 ± 0.61 days) was significantly shorter than Diet 2 (26.15 ± 0.71 days) and Diet 4 (26.41 ± 0.38 days). The overall results revealed that Diet 3 showed good results at different life table parameters of Ae. aegypti and can be used as the preferred diet in the Sterile Insect Technique (SIT) where the mass culture of mosquitoes is required.

Tree canopy cover affects basal resources and nutrient profiles of Aedes and Culex larvae in cemetery vases in New Orleans, Louisiana, United States

Cemetery vases are important habitat for vector mosquito production, yet there is limited understanding on their food web dynamics and how they vary across environmental gradients. Tree cover is one factor that varies widely across cemeteries, and influence food webs by means of detrital inputs, temperature mediation, and light availability. Such information can be important for determining mosquito adult body size, fecundity, and competition outcomes, all of which may influence mosquito population and disease risk. This study evaluates the relationship between tree canopy cover and indicators of basal resources for Aede aegypti (L.), Aedes albopictuss (Skuse), and Culex quinquefasciatus (Say) larvae, such as stable isotopes (δ13C and δ15N) and nutrient stoichiometry in cemeteries of New Orleans, Louisiana (USA). Stable isotope values suggest that larvae feed directly on the Particulate Organic Matter (POM) suspended in the vase's water, and that POM composition influence the nutrient profiles of mosquito larvae. The POM of open canopy vases had higher δ13C values, than that of closed canopy vases indicating differences in relative proportion of basal carbon sources, with open canopy POM having a lower proportion of allochthonous carbon, and a higher proportion of authoctonous carbon. Accordingly, mosquito larvae collected from open canopy vases had higher δ13C values, and higher C:N than larvae from closed canopy vases. The results of this study show a shift in food web dynamics driven by canopy cover in cemetery vases that directly influence the nutrient profiles of mosquito larvae. The implications for mosquito ecology, and vector management are discussed.

Insects to feed insects - feeding Aedes mosquitoes with flies for laboratory rearing

The black soldier fly, yellow mealworm and house fly are known for their wide distribution, ease of breeding, and environmental and nutritional attributes. Diets based on these fly proteins for the rearing of mosquito larvae are more accessible and affordable when compared to the reference IAEA diet which consists largely of costly livestock products such as bovine liver powder. Following a step-by-step assessment, we developed diet mixtures based on insect meal for the optimal mass production of Aedes albopictus and Ae. aegypti. Based on the assessed parameters including mosquito egg hatch, body size, flight ability, longevity and diet cost reduction, two mixtures are recommended: 1/2 tuna meal (TM) + 7/20 black soldier fly (BSF) + 3/20 brewer’s yeast and 1/2 TM + 1/2 BSF. These findings, which could be adapted to other mosquito species, provide alternative protein sources for mass rearing insects for genetic control strategies.

Performance of five food regimes on Anopheles gambiae senso stricto larval rearing to adult emergence in insectary

Background

Rearing of Anopheles gambiae s.s mosquitoes in insectary with quality cheap food sources is of paramount importance for better and healthy colony. This study evaluated larval survival and the development rate of aquatic stages of An.gambiae s.s under five food regimes; tetramin fish food (a standard insectary larval food), maize pollen, Cerelac, green filamentous algae and dry powdered filamentous algae.

Methods

Food materials were obtained from different sources, cerelac was made locally, fresh filamentous algae was taken from water bodies, dry filamentous algae was ground to powder after it was dried under shade, and maize pollen was collected from the flowering maize. Each food source type was used to feed three densities of mosquito larvae 20, 60, and 100 in six replicates each. Larval age structure was monitored daily until pupation and subsequently adult emergence. Tetramin was used and taken as a standard food source for An. gambiae s.s. larvae feeding in Insectary.

Results

Larval survivorship using maize pollen and Tetramin fish food was statistically insignificant (P = 0.564). However when compared to other food regime survivorship was significantly different with Tetramin fish food performing better than cerelac (P<0.001), dry algae (P<0.001) and fresh algae (P<0.001). The pupation rates and sex ratio of emerging adults had significant differences among the food regimes.

Conclusion

The findings of this study have shown that maize pollen had closely similar nutritional value for larval survivorship to tetramin fish food, a standard larvae food in insectary. Further studies are required to assess the effect of food sources on various life traits of the emerged adults.

Life stage-related differences in fatty acid composition of an obligate ectoparasite, the deer ked (Lipoptena cervi)-influence of blood meals and gender

Metamorphosis and diet often influence fatty acid (FA) signatures (FAS) of insects. We investigated FAS in a hematophagous ectoparasite, the deer ked (Lipoptena cervi). Deer keds shed their wings upon attachment on the host and, thus, the FAS of an individual blood-fed imago/pupa in the fur of its host can be traced back to the blood FA profile of a single moose (Alces alces). Host blood and different life stages of deer keds were investigated for FA by gas chromatography. The FAS of life stages resembled each other more closely than the diet. Blood meals modified the FAS of both sexes but the FAS of the blood-fed females were closer to those of the prepupae/pupae. The parasitizing males had higher proportions of major saturated FA (SFA) and polyunsaturated FA (PUFA) than the females, which contained more monounsaturated FA (MUFA) with higher ratios of n-3/n-6 PUFA and unsaturated FA (UFA)/SFA. The proportions of 16:1n-7 were <1% in the blood but 18% (males) and 29% (females) in the blood-fed keds. Allocation of lipids to offspring by the females and possible accumulation of PUFA in male reproductive organs may have induced these sex-related differences. MUFA percentages and UFA/SFA ratios increased while SFA and many PUFA decreased from the reproducing females to the pupae. The diapausing pupae displayed lowered n-3/n-6 PUFA ratios and could have mobilized 16:0 and 18:3n-3 for the most fundamental metabolic processes. In conclusion, FAS are modified through the life stages of the deer ked possibly due to their different FA requirements.

Development of inexpensive and globally available larval diet for rearing Anopheles stephensi (Diptera: Culicidae) mosquitoes

Background

Success of sterile insect technique (SIT) is dependent upon the mass rearing and release of quality insects, the production of which is directly related to the suitability of the diet ingredients used. Commercial diets used for small-scale culture of mosquitoes are expensive and thus not feasible for mass production.

Methods

A series of low cost globally available diet ingredients including, wheat, rice, corn, chickpeas, and beans along with liver, were provided to 4 h larvae (L1) of Anopheles stephensi (Liston) to see their effect on fitness parameters including larval duration, percent emergence, survival, adult wing size and female fecundity. Different quantities of the candidate diet ingredients were then mixed together to work out a combination diet with a balanced nutritive value that can be used for efficient rearing of the mosquito larvae at relatively lower costs.

Results

Fastest larval and pupal development and highest survival rates were recorded using a combination diet of bean, corn, wheat, chickpea, rice, and bovine liver at 5 mg/day. The diet is easy to prepare, and much cheaper than the diets reported earlier. The estimated cost of the reported diet is 14.7 US$/ 1.3 kg for rearing one million larvae.

Conclusions

A combination diet with ingredients from cereals and legumes mixed with liver is a low cost balanced larval diet with the potential for use in both small scale laboratory rearing and mass production of Anopheles in SIT control programs.

An analysis of diet quality, how it controls fatty acid profiles, isotope signatures and stoichiometry in the malaria mosquito Anopheles arabiensis

BACKGROUND

Knowing the underlying mechanisms of mosquito ecology will ensure effective vector management and contribute to the overall goal of malaria control. Mosquito populations show a high degree of population plasticity in response to environmental variability. However, the principle factors controlling population size and fecundity are for the most part unknown. Larval habitat and diet play a crucial role in subsequent mosquito fitness. Developing the most competitive insects for sterile insect technique programmes requires a "production" orientated perspective, to deduce the most effective larval diet formulation; the information gained from this process offers us some insight into the mechanisms and processes taking place in natural native mosquito habitats.

METHODOLOGY/PRINCIPAL FINDINGS

Fatty acid profiles and de-novo or direct assimilation pathways, of whole-individual mosquitoes reared on a range of larval diets were determined using pyrolysis gas chromatograph/mass spectrometry. We used elemental analysis and isotope ratio mass spectrometry to measure individual-whole-body carbon, nitrogen and phosphorous values and to assess the impact of dietary quality on subsequent population stoichiometry, size, quality and isotopic signature. Diet had the greatest impact on fatty acid (FA) profiles of the mosquitoes, which exhibited a high degree of dietary routing, characteristic of generalist feeders. De-novo synthesis of a number of important FAs was observed. Mosquito C:N stoichiometry was fixed in the teneral stage. Dietary N content had significant influence on mosquito size, and P was shown to be a flexible pool which limited overall population size.

CONCLUSIONS/SIGNIFICANCE

Direct routing of FAs was evident but there was ubiquitous de-novo synthesis suggesting mosquito larvae are competent generalist feeders capable of survival on diet with varying characteristics. It was concluded that nitrogen availability in the larval diet controlled teneral mosquito size and that teneral CN ratio is a sex- and species-specific fixed parameter. This finding has significant implications for overall mosquito competitiveness and environmental management.

An inexpensive and effective larval diet for Anopheles arabiensis (Diptera: Culicidae): eat like a horse, a bird, or a fish?

A successful sterile insect technique program depends upon mass production of good-quality sterile insects for release into a target area. Specifically, to control Anopheles arabiensis Patton (Diptera: Culicidae) in a pilot area in northern Sudan, 1 million An. arabiensis sterile males per day are needed. To reach this production objective, mosquito mass rearing is indispensable and larval diet, a key parameter for the production of healthy male mosquitoes, needs to be cost-effective. The Koi Floating Blend fish food, previously used at the Food and Agriculture Organization/International Atomic Energy Agency Insect Pest Control Laboratory for the routine rearing of the An. arabiensis colony, is no longer available. The aim of this study was to find a cheap and effective substitute for the discontinued diet. Several candidate powdered diets that are commercially available were tested to determine the best diet. By using mixture experiment principles and response surface methodology, the combination of two components, bovine liver powder and tuna meal, showed the best results in terms of larval survival, developmental, rate and adult size. The addition of a vitamin mixture further improved the diet. These positive production results coupled with the relatively low cost of our blend demonstrated the possibility of its use for mass rearing purpose.