Microorganism-Based Larval Diets Affect Mosquito Development, Size and Nutritional Reserves in the Yellow Fever Mosquito Aedes aegypti (Diptera: Culicidae)

Abstract

Background Mosquito larvae feed on organic detritus from the environment, particularly microorganisms comprising bacteria, protozoa, and algae as well as crustaceans, plant debris, and insect exuviae. Little attention has been paid to nutritional studies in Aedes aegypti larvae. Objectives We investigated the effects of yeast, bacteria and microalgae diets on larval development, pupation time, adult size, emergence, survivorship, lifespan, and wing morphology. Materials and Methods Microorganisms (or Tetramin ® as control) were offered as the only source of food to recently hatched first instar larvae and their development was followed until the adult stage. Protein, carbohydrate, glycogen, and lipid were analyzed in single larvae to correlate energetic reserve accumulation by larva with the developmental rates and nutritional content observed. FITC-labeled microorganisms were offered to fourth instar larvae, and its ingestion was recorded by fluorescence microscopy and quantitation. Results and Discussion Immature stages developed in all diets, however, larvae fed with bacteria and microalgae showed a severe delay in development rates, pupation time, adult emergence and low survivorship. Adult males emerged earlier as expected and had longer survival than females. Diets with better nutritional quality resulted in adults with bigger wings. Asaia sp. and Escherichia coli resulted in better nutrition and developmental parameters and seemed to be the best bacterial candidates to future studies using symbiont-based control. The diet quality was measured and presented different protein and carbohydrate amounts. Bacteria had the lowest protein and carbohydrate rates, yeasts had the highest carbohydrate amount and microalgae showed the highest protein content. Larvae fed with microalgae seem not to be able to process and store these diets properly. Larvae were shown to be able to process yeast cells and store their energetic components efficiently. Conclusion Together, our results point that Ae. aegypti larvae show high plasticity to feed, being able to develop under different microorganism-based diets. The important role of Ae. aegypti in the spread of infectious diseases requires further biological studies in order to understand the vector physiology and thus to manage the larval natural breeding sites aiming a better mosquito control.

Yeast-encapsulated essential oils: a new perspective as an environmentally friendly larvicide

“…It has been reported that Ae. aegypti larvae, after reaching a critical body mass, stop eating and start preparation to metamorphosis if exposed to stressing factors, like xenobiotics or food with low nutritional value [37]. In this respect, the EO-yeast particles might be inducing pupation in L4 larvae, and that is consistent with the hypothesis that ingestion of the larvicide is an important step in its mechanism of action.…”

Determination of Chitin Content in Insects: An Alternate Method Based on Calcofluor Staining

“…The same tendency is seen in A. aegypti, with females having about 47 µg chitin/insect, and males around 25 µg of chitin per insect. The females tend to be larger than males in both cases and may have eggs in the ovaries (Farnesi et al, 2015;Souza et al, 2019), which would account for the differences seen in measurements. Rhodnius prolixus first instar nymphs have 41 µg of chitin/insect, and adult males increase this total to a mean of 4600 µg/insect, an enhancement of 1000 fold in the concentration of the polymer, which is consistent with the growth of the insects.…”

The effect of resource limitation on the temperature-dependence of mosquito population fitness

“…This is because microbial growth rates increase with temperature to some optimum, which may increase the concentration of food in the environment [8,70,71]. For example, Anopheles [72] and Aedes [73] mosquitoes can be reared exclusively on cultures of Asaia bacteria. The temperature-dependence of resource supply is an interesting and potentially important avenue of investigation that would further elucidate how the interaction between temperature and resource availability affects the fitness of mosquitoes.…”