Go home mosquito, you are confused!

We often experience confusion when faced with too many options. For example, imagine you entered a hypermarket to buy a jar of jam but came back without buying anything as there were more than twenty options to choose from and you just couldn’t decide. It turns out that mosquitoes too, get overwhelmed by an overload of choice when they set out to decide where to lay eggs.

A study conducted by researchers from Ashoka University and the Indian Institute of Science, Bengaluru, tested how large choice repertoires impact decision-making in the Asian tiger mosquito, Aedes aegypti.

This study investigated the mosquitos’ egg-laying behaviour and revealed that when overwhelmed with too many choices, mosquitoes stop paying attention to the presence of predators. Instead, mosquitoes may adopt alternative strategies for egg-laying, such as bet-hedging where they distribute eggs in multiple pools. Bet hedging is a strategy used by organisms in uncertain or variable environments to increase their chances of survival and reproductive success over time.

This finding has important implications for mosquito control strategies. Currently, biological control methods, such as the release of mosquito fish, Gambusia affinis, in water bodies, are thought to be effective in preventing mosquitoes from laying eggs. However, we might need to consider how choice overload affects mosquitoes and test how effective these biological control methods really are.

The researchers also explore a broader question about animal behaviour. They challenge the predictions from rational choice theory, which states that options presented to a chooser have fixed reward values and are independent of the context in which the choice is made.

In other words, this concept of rational choice theory from economics and decision theory is often used to understand human behaviour. It assumes that individuals make decisions based on a rational evaluation of available options, aiming to maximise their utility or satisfaction. However, there is now a growing body of evidence which suggests that animals fail to choose the options predicted by rational choice theory in multiple contexts – females choosing mates or foraging honeybees choosing flowers for nectars.

Lead author Manvi Sharma, Assistant Professor of Environmental Studies at Ashoka University, explains that animals need to acquire information for making decisions, and in complex environments, this can be a costly exercise. These costs may lead to the evolution of bet-hedging in mosquitoes, i.e., spreading eggs in multiple pools. But we have no clue if other animals also use bet-hedging strategies.

The experiments done in the study also demonstrate that frugal science can contribute to the progress of scientific knowledge. The researchers conducted choice trials in the backyard of the field research station using plastic tubs and a microscope to count eggs. If we had known about foldscopes back then, we could have saved more resources, says the lead author.

The project was funded by the Department of Biotechnology – Indian Institute of Science (DBT-IISc) partnership grant.

(Edited by Dr. Yukti Arora, Senior Manager, Academic Communications, RDO, Ashoka University)

Reference Article:
Spoilt for choice: Do female mosquitoes experience choice overload when deciding where to lay eggs?
doi.org/10.1016/j.beproc.2023.104963

Authors: Manvi Sharma and Kavita Isvaran