No Impact of Biocontrol Agent's Predation Cues on Development Time or Size of Surviving Aedes albopictus under Optimal Nutritional Availability.

Marie C Russell,Lauren J Cator

doi:10.3390/insects13020155

Abstract

Simple SummaryAedes albopictus is a highly invasive species of mosquito that can infect humans with chikungunya, dengue, yellow fever, and Zika. Within the next few decades, this mosquito species is predicted to invade South East England. Cyclopoid copepods are small crustaceans that have previously been used as biocontrol agents due to their high efficiency at killing small early instar mosquito larvae. We assessed the effect of Megacyclops viridis, a copepod species local to South East England, on the survival and traits of mosquito larvae exposed to these predators during the larger late instar stage. Our experiment was designed to measure the impact of copepod predation on both the development time and adult body size of Ae. albopictus. These traits can shape mosquito population dynamics and disease transmission. While we found that copepod attacks cause a small increase in late instar mortality, our methods did not detect a significant difference in either development time or size between the predator and control treatments. The lack of a strong sublethal effect on these traits supports the use of M. viridis copepods as biocontrol agents against Ae. albopictus in the UK. This information may be useful for guiding public health measures that aim to prevent outbreaks of mosquito-borne disease.Cyclopoid copepods have been applied successfully to limit populations of highly invasive Aedes albopictus mosquitoes that can transmit diseases of public health importance. However, there is concern that changes in certain mosquito traits, induced by exposure to copepod predation, might increase the risk of disease transmission. In this study, third instar Ae. albopictus larvae (focal individuals) were exposed to Megacyclops viridis predator cues associated with both the consumption of newly hatched mosquito larvae and attacks on focal individuals. The number of newly hatched larvae surrounding each focal larva was held constant to control for density effects on size, and the focal individual’s day of pupation and wing length were recorded for each replicate. Exposing late instar Ae. albopictus to predation decreased their chances of surviving to adulthood, and three focal larvae that died in the predator treatment showed signs of melanisation, indicative of wounding. Among surviving focal Ae. albopictus, no significant difference in either pupation day or wing length was observed due to copepod predation. The absence of significant sublethal impacts from M. viridis copepod predation on surviving later stage larvae in this analysis supports the use of M. viridis as a biocontrol agent against Ae. albopictus.

Highlights

Aedes albopictus is an important vector of dengue, chikungunya, yellow fever, and Zika [1]
While cyclopoid copepod predation by M. viridis significantly increases the mortality of late instar Ae. albopictus, related predation cues do not significantly change the development time or adult size of those late instar Ae. albopictus that survive, assuming optimal nutritional availability
A small increase in mortality among late instar larvae due to predation, such as the 10% increase shown in this study, is unlikely to result in increased body size among surviving late instars, especially when nutrients are available at high levels, as is often the case in Ae. albopictus larval habitats observed in the field [65]

Summary

Introduction

Aedes albopictus is an important vector of dengue, chikungunya, yellow fever, and Zika [1]. This species is highly invasive, in part due to its ability to lay desiccation-resistant eggs that can be transported across long distances, often by the shipment of used tires [2,3,4,5,6]. The sterile insect technique (SIT) was tested on Ae. albopictus mosquitoes from Italy, but it did not significantly reduce their population due to detrimental effects on mating competitiveness among irradiated males [11]. Cyclopoid copepods were used successfully as biocontrol agents against mosquito larvae in the US [12], Australia [13], Vietnam [14], and Italy [15]. Exposure to predators over multiple generations can result in greater mosquito population performance, as measured by a composite index of performance (r’) that takes mosquito wing length into account [17,18]

Methods

Results

Discussion

Conclusion