The Cator Lab

@ Imperial College London

The behavioural ecology of mosquitoes

Mosquito transmitted pathogens have an enormous impact of human health. A substantial amount of funding and resources are being spent to control the transmission of diseases such as malaria and dengue fever. In many ways this investment is paying off. Innovative and exciting new strategies and technologies have been developed to help combat these plagues.  Improving our knowledge of mosquito behaviour and ecology will help us effectively control disease.   Our research aims to improve understanding of mosquito behaviour and how behaviour mediates interactions with other organisms, the parasites that they transmit, and the dynamic world that they live in.

Sex in a Swarm

Most medically important mosquitoes mate in aerial swarms. The aggregations are primarily composed of males with fewer numbers of female entering and mating. The entire mating event occurs in flight and in a matter of seconds. Despite the importance of mating in mosquito biology and the many control tools targeting reproductive biology, we understand relatively little about what is going on in these swarms. Currently most of the projects in the lab focus on these aggregations and the behavioral ecology of mating. 

What traits are associated with male mating success?

In order to give laboratory released males the best possible chance to compete with wild males we need to understand what traits are associated with male mating success.  It will also be important to understand to what degree female preferences affect this mating success. We are interested in identifying these traits both in the laboratory and in the field. I'm excited to work with Dr. Courtney Murdock at the University of Georgia and Laura Harrington at Cornell University on these questions. 

Do male mosquitoes signal information about their quality to females?  

When male and female meet in flight they alter their flight tone (that annoying buzz they beat their wings).  They change the frequency of their flight tone to match at overtones. We have found that males adjust this response depending on the perceived quality of females and that harmonic convergence signals appear to be correlated with heritable mating success. Better understanding these putative courtship signals may help us answer some long standing questions about what happens in mosquito mating swarms.  

To what degree does the female instead of the male determine the identity of successful males?

A major challenge to understanding what happens in swarms is the high speed at which they occur. We are developing tools that allow us to more precisely measure these behaviours. We developed a system that allows for synchronized high-speed video and audio recording of male and female interactions. We have found that while males are aggressive and persistent females are able to refuse matings. (See more of Andy's awesome videos here)

To what degree is male mating success due to environmental and genetic factors?  

Control of Ae. aegypti populations is vital for reducing the transmission of several pervasive human diseases. The success of new vector control technologies will be influenced by the fitness of laboratory-reared transgenic males. However, there has been relatively little published data on how rearing practices influence male fitness in Aedes mosquitoes. In laboratory experiments we have found that larval food availability was demonstrated to be positively correlated with adult body size, survival, and increased swarming activity. However, we also found that within a swarm larger males did not have an increased likelihood of copulating with a female. These results suggest that while increasing larval diet may improve the opportunities for males (increased swarming and survival).

When we investigated the effect of larval diet amount on adult male mating success in a genetically modified strain of Ae. aegypti in competition with wild-type conspecifics we found that food quantity did not affect male mating fitness. We used multiple laboratory and field based measures to assess mating performance. Regardless of diet, males from low generation (<F4) laboratory populations consistently outcompeted wild F1 males for wild F1 females in laboratory assays. Strikingly, when males from the same populations were competed under field conditions, we observed no such increase in performance. The increased performance of our low generation laboratory lines suggests that adaptation to laboratory conditions can occur in a very short amount of time. The findings also demonstrate that laboratory adaptation can influence the perceived quality of lines intended for mass release and highlight the need to incorporate field-based measurements of mating performance as part of control evaluations.