MSc Research

'Time flies like an arrow, fruit flies like a banana'

We have all witnessed fruit flies hovering over a clutch of bananas in our kitchen, the older the better! My research delved into understanding the neurobiology of taste in fruit flies.

Animals are inherently attracted towards sweet compounds which helps them in fulfilling their calorie needs while they are averse to bitter compounds which are mostly associated with toxic substances like denatonium, caffeine, etc. A fly uses not only its proboscis but also its tarsi which is the fifth segment of its legs to evaluate and taste compounds. These organs are decorated with hair-like structures called the sensilla which house different taste neurons. When the fly walks over a bitter compound assessing it, it leads to the firing of the bitter taste neurons which elicits an aversive response in the fly, however, when it comes across a sweet compound, it leads to the firing of the sweet taste neurons and the fly extends its proboscis as an appetitive response. But what about sour taste? We might prefer a dash of vinegar in french fries but surely not hydrochloric acid. How does the brain essentially decide what is appetitive and what is aversive on the basis of taste? 

To understand sour taste mechanisms we decided to delve into studying the gustatory mechanisms of lactic acid taste, which at a lower concentration is appetitive and beneficial for the body. However, at higher concentrations, it is corrosive like most acids.

This was both the more fun as well as the blood-draining (literally!) part of my thesis! Female Aedes aegypti are hematophagous in nature, that is they utilize the protein from the blood they draw to mature their eggs.

Lactic acid is a predominant component of human sweat, which we reasoned could be a potential bite initiation cue for the female Aedes aegypti mosquitoes. They integrate a number of sensory cues like olfactory, visual, thermal, and gustatory cues while seeking a host.  We wanted to evaluate whether lactic acid on human skin was an appetite cue for the female mosquitoes, which elicited the engorgement behavior. 

However, crafting a suitable engorgement assay to evaluate taste preference was a rocky road. The fly two-choice assay could not be adapted to the mosquitoes owing to their different morphology and homeostasis-dependent feeding behavior. Only gravid female mosquitoes engorged on blood, while virgin females and males would fulfill their nutrient requirement from nectar feeding.  After many rounds of trial and error, we could craft a robust assay to evaluate female engorgement preference. We also adapted the assay to evaluate feeding preference in males.