Larval feeding duration affects ecdysteroid levels and nutritional reserves regulating pupal commitment in the yellow fever mosquitoAedes aegypti(Diptera: Culicidae)

Abstract

SUMMARY What little is known about the endocrine regulation of mosquito development suggests that models based on Lepidoptera and Drosophila may not apply. We report on basic parameters of larval development and the commitment to metamorphosis in the yellow fever mosquito Aedes aegypti that are affected by varying the length of feeding time for last instar larvae. A critical mass for pupal commitment was achieved after 24 h of feeding by last instars, also the age at which tissue production and hemolymph titers of ecdysteroids are increasing. A greater proportion of last instars successfully pupated and eclosed as adults as the length of their feeding time increased. Less than 24 h of feeding time resulted in last instars that were developmentally arrested; these larvae tolerated starvation conditions for up to 2 weeks and retained the capacity to pupate if re-fed. Starvation tolerance may be a common trait among container-inhabiting species, and this period is an important factor to be considered for vectorial capacity and control measures. To distinguish cues for metamorphosis related to a larva's nutritional status versus its age, newly molted last instars were fed for different periods of time but sampled at the same age; ecdysteroid levels,body mass and nutrient reserves were then measured for each group. Our data suggest that metamorphic capacity is dependent on a larva's nutritional condition and not just the age at which ecdysteroid titers increase. Last instars that have fed for a particular length of time may initiate their metamorphic molt when both threshold levels of nutrient reserves and ecdysteroid titer have been met. Future studies will lead to a conceptual model specific for the nutritional and hormonal regulation of mosquito post-embryonic development. This model should facilitate the exploitation of current and novel insect growth regulators that are among favored strategies for vector population suppression.

Physical characteristics and reproductive performance in Aedes (Diptera: Culicidae)

“…The small-sized males and females (SMs and SFs) tested here were produced by rearing 200 newly hatched larvae with limited food supplies, whereas LMs and LFs were generated by raising 100 first instar larvae with an abundant food supply. Larvae maintained in a highly nutritious environment have more energy stores than those reared under cro wded conditions with inadequate nutrition (Telang et al, 2007). All had similar sugar feeding opportunities.…”

Testing mechanistic models of growth in insects

“…Among these species it has been variously found that commitment to moulting is triggered by abdominal stretch receptors [37], the exhaustion of a prepackaged food supply [38], or size-imposed oxygen limitation [39]. More recently it has been found that nutritional condition may better describe the process of moulting [40][41][42]. As the DEB model considers both size (structure) and nutritional condition (reserve), it offers natural handles to both of these quantities, which could be used to explore developmental triggers in insects.…”

Comparative account of energy reserves in four co-occurring mosquito species in Kolkata, India (Diptera: Culicidae)

“…Following eclosion, the water in the glass vials was removed and the glass vials along with the adult mosquitoes were stored at -20°C for 2 hours to kill the insects. Then the vials were placed in a hot air oven with a temperature of 40°C maintained for 48 hours to dry the samples, following the protocol used elsewhere (TELANG et al 2006(TELANG et al , 2007. This process was adopted for adults emerging within a 2 hour time frame; the remainder were continuously monitored for eclosion to adult stage.…”