Biology subjects

Lazzari, C. R.

Publications and source records attributed to Lazzari, C. R..

5 recordsLinked to original sources

bioRxiv2026

Passive copper release from ornamental rain chains is harmful to mosquito larvae and deters egg-laying

Urban mosquitoes use accumulated rainwater in private gardens and public green spaces for reproduction. We found that ornamental copper chains, which direct rainwater from gutters into open containers, can significantly reduce the number of mosquito larvae in the collected water, sometimes eliminating them entirely. Although the impact of copper salts or copper objects in water on mosquito larvae is well documented, a detailed analysis of the effects of dissolved copper in terms of concentration and biological impact has yet to be conducted. In this study, we present the results of two experimental analyses: one conducted in gardens and the other in the laboratory. These experiments were designed to corroborate consistent, albeit circumstantial, observations, and to describe the sensitivity of mosquito larvae to rainwater containing low quantities of copper. Field experiments were conducted during a period of high tiger mosquito (Aedes albopictus) abundance, while laboratory experiments used the yellow fever mosquito (Aedes aegypti) as a biological model. Our field experiments revealed that rain chains release sufficient copper into the water to drastically reduce the number of juvenile mosquitoes. In the laboratory, rainwater containing copper released by the chains affected hatching and larval development; however, the most significant effect was that females laid almost no eggs in the presence of copper-containing water.

zoology↗

bioRxiv2023

Mosquitoes do not like bitter: new perspectives for biorational repellents

Chemical repellents play a crucial role in personal protection, serving as essential elements in reducing the transmission of vector-borne diseases. A biorational perspective that extends beyond the olfactory system as the classical target may be a promising direction to move. The taste system provides reliable information regarding food quality, helping animals discriminate between nutritious and potentially harmful food sources, often associated with a bitter taste. Understanding how bitter compounds affect feeding in blood-sucking insects could unveil novel molecules with the potential to reduce biting and feeding. Here, we investigated the impact of two naturally occurring bitter compounds, caffeine and quinine, on the feeding decisions in female Aedes aegypti mosquitoes at two distinctive phases: (1) when the mosquito explores the biting substrate using external taste sensors and (2) when the mosquito takes a sip of food and tastes it using internal taste receptors. We assessed the aversiveness of bitter compounds through both an artificial feeding condition (artificial feeder test) and a real host (arm-in-cage test). Our findings revealed different sensitivities in the external and internal sensory pathways responsible for detecting bitter taste in Ae. aegypti. Internal detectors exhibited responsiveness to lower doses compared to the external sensors. Quinine exerted a more pronounced negative impact on biting and feeding activity than caffeine. The implications of our findings are discussed in the context of mosquito food recognition and the potential practical implications for personal protection.

zoology↗

bioRxiv2023

Challenging popular belief, mosquito larvae breathe underwater

It is taken for granted that immature mosquito only breathe atmospheric air through their siphons. However, there is no quantitative study that demonstrated it. We analysed the survival of the last instar larvae of Aedes aegypti fully submerged at different temperatures, and measured oxygen consumption from air and dissolved in water, of larvae and pupae of this species under different conditions. Results revealed that under water, larvae survived much longer than expected, reaching 50% mortality only after 58, 10, and 5 days at 15{degrees}, 25{degrees} and 35{degrees}C, respectively. Interestingly, whereas we registered moults to pupae in larvae with access to air, individuals kept submerged never moulted. When remaining at the water surface, larvae obtained 12.72% of O2 from the water, while pupae only 5.32%. When completely submerged, larvae consumed less oxygen than in contact with the surface, but enough for surviving, while pupae did not. At both media, temperature affected larvae respiration rate, with relatively close Q10 values. In the related species, Ae. albopictus, a similar pattern of O2 consumption were observed. Larvae got 12.14% of their oxygen from the water. Interestingly, no significant differences in total O2 consumption were found between water O2 consumption, when Ae. albopictus larvae were submerged, or when they also have access to air (dual O2 consumption). Our findings not only challenge the classical idea that mosquito larvae only breathe atmospheric O2, but also force us to reconsider the potential effectiveness of control methods based on asphyxiating larvae by detaching from water surface. Summary statementWe present the first quantitative analysis of mosquito larvae respiration in air and water, unravelling the unknown capacity of larvae of the most cosmopolitan disease vector of breathing underwater.

zoology↗

bioRxiv2020

Response to thermal and infection stresses in an American vector of visceral leishmaniasis.

The phlebotomine sand fly Lutzomyia longipalpis is the primary insect vector of visceral leishmaniasis in the Americas. For ectothermic organisms such as sand flies, the ambient temperature is a critical factor influencing all aspects of their life. However, the impact of temperature has been ignored in previous investigations of stress-induced responses by the vector, such as taking a blood meal or during Leishmania infection. Therefore, this study explored the interaction of Lu. longipalpis with temperature by evaluating sand fly behaviour across a thermal gradient after sugar or blood-feeding, and infection with Leishmania mexicana. Thermographic recordings of sand fly females fed on mice were analysed, and the gene expression of heat shock proteins HSP70 and HSP90(83) was evaluated when insects were exposed to extreme temperatures or infected. The results showed that 72h after blood ingestion females of Lu. longipalpis became less active and preferred relatively low temperatures. However, at later stages of blood digestion females increased their activity and remained at higher temperatures prior to taking a second blood meal; this behaviour seems to be correlated with the evolution of their oocysts and voracity for a second blood meal. No changes in the temperature preferences of female sand flies were recorded in the presence of a gut infection by Le. mexicana, indicating that this parasite has not triggered behavioural immunity in Lu. longipalpis. Real-time imaging showed that the body temperature of female flies feeding on mice increased to the same temperature as the host within a few seconds after landing. The body temperature of females remained around 35 {+/-} 0.5 {degrees}C until the end of blood-feeding, revealing a lack of thermoregulatory behaviour. Analysis of expression of heat shock proteins revealed insects increased expression of HSP90(83) when exposed to higher temperatures, such as during blood feeding. Our findings suggest that Lu. longipalpis interacts with the environmental temperature by using its behaviour to avoid temperature-related physiological damage during the gonotrophic cycle. However, the expression of certain heat shock proteins might be triggered to mitigate against thermal stress in situations where a behavioural response is not the best option.

microbiology↗

bioRxiv2020

Soft ticks perform evaporative cooling during blood-feeding

Feeding on the blood of warm-blooded vertebrates is associated to thermal stress in haematophagous arthropods. It has been demonstrated that blood-sucking insects protect their physiological integrity either by synthesising heat-shock proteins or by means of thermoregulatory mechanisms. In this work, we describe the first thermoregulatory mechanism in a tick species, Ornithodoros rostratus. By performing real-time infrared thermography during feeding on mice we found that this acarian eliminates big amounts of fluid (urine) through their coxal glands; this fluid quickly spreads over the cuticular surface and its evaporation cools-down the body of the tick. The spread of the fluid is possible thanks to capillary diffusion through the sculptured exoskeleton of Ornithodoros. We discuss our findings in the frame of the adaptive strategies to cope with the thermal stress experienced by blood-sucking arthropods at each feeding event warm-blooded hosts.

zoology↗