Quantitative Evaluation of the Behavioral Response to Attractant and Repellent Compounds in Anopheles pseudopunctipennis and Aedes aegypti (Diptera: Culicidae) Larvae.

The mosquito Anopheles pseudopunctipennis (Theobald) is the principal vector for malaria in Latin-America. Aedes aegypti (L.) (Diptera: Culicidae) is the key vector of four important arboviral diseases: dengue, yellow fever, Zika, and chikungunya. Controlling larval stages to reduce the production of new adult mosquitoes is part of the integrated vector management strategies. However, there are few studies about the olfactory behavior on immature stages of mosquitoes, especially in An. pseudopunctipennis. In this work, we have evaluated the behavior of An. pseudopunctipennis and Ae. aegypti larvae in response to attractant or repellent stimuli through a video-tracking analysis. We used the software EthoVision to obtain behavioral variables related to the swimming activity, such as distance, speed, and mobility status. The response to the repellents stimulus results in an increase of the swimming activity and the absolute angular velocity in both species. Otherwise, the responses to the possible attractants stimulus results in a decrease of the activity of the larvae only for Ae. aegypti. The effects of these compounds were weaker in Anopheles; probably as a consequence of their adaptations to different aquatic ecosystems. The study of the larval olfactory response could contribute to the development of new control tools based on 'push-pull' strategies by 'pushing' mosquitoes away from certain places using repellents, and 'pulling' them towards other places like traps baited with attractive cues.

Effect of Environmental Conditions and Toxic Compounds on the Locomotor Activity of Pediculus humanus capitis (Phthiraptera: Pediculidae).

In this work, we evaluated the effect of environmental variables such as temperature, humidity, and light on the locomotor activity of Pediculus humanus capitis. In addition, we used selected conditions of temperature, humidity, and light to study the effects of cypermethrin and N,N-diethyl-3-methylbenzamide (DEET) on the locomotor activity of head lice. Head lice increased their locomotor activity in an arena at 30°C compared with activity at 20°C. When we tested the influence of the humidity level, the locomotor activity of head lice showed no significant differences related to humidity level, both at 30°C and 20°C. Concerning light influence, we observed that the higher the intensity of light, the slower the movement of head lice. We also demonstrated that sublethal doses of toxics may alter locomotor activity in adults of head lice. Sublethal doses of cypermethrin induced hyperactivated responses in adult head lice. Sublethal doses of DEET evocated hypoactivated responses in head lice. The observation of stereotyped behavior in head lice elicited by toxic compounds proved that measuring locomotor activity in an experimental set-up where environmental conditions are controlled would be appropriate to evaluate compounds of biological importance, such as molecules involved in the host-parasite interaction and intraspecific relationships.