Effects of temperature and photoperiod on daily activity rhythms of Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract

BackgroundInsect vectors have been established as models in Chronobiology for many decades, and recent studies have demonstrated a close relationship between the circadian clock machinery, daily rhythms of activity and vectorial capacity. Lutzomyia longipalpis, the primary vector of Leishmania (Leishmania) infantum in the New World, is reported to have crepuscular/nocturnal activity in the wild. However, most of these studies applied hourly CDC trap captures, which is a good indicative of L. longipalpis behaviour, but has limited accuracy due to the inability to record the daily activity of a single insect during consecutive days. In addition, very little is known about the activity pattern of L. longipalpis under seasonal variations of average temperature and day length in controlled laboratory conditions.MethodsWe recorded the locomotor activity of L. longipalpis males under different artificial regimes of temperature and photoperiod. First, in order to test the effects of temperature on the activity, sandflies were submitted to regimes of light/dark cycles similar to the equinox photoperiod (LD 12:12) combined with different constant temperatures (20°C, 25°C and 30°C). In addition, we recorded sandfly locomotor activity under a mild constant temperature (25°C with different day length regimes: 8 hours, 12 hours and 16 hours).ResultsL. longipalpis exhibited more activity at night, initiating dusk-related activity (onset time) at higher rather than lower temperatures. In parallel, changes of photoperiod affected anticipation as well as all the patterns of activity (onset, peak and offset time). However, under LD 16:08, sandflies presented the earliest values of maximum peak and offset times, contrary to other regimes.ConclusionsHerein, we showed that light and temperature modulate L. longipalpis behaviour under controlled laboratory conditions, suggesting that sandflies might use environmental information to sustain their crepuscular/nocturnal activity, as well as other important aspects as mating and host-seeking at appropriate times in different seasons. Our results depict previously unappreciated aspects of the L. longipalpis daily rhythms of activity that might have important epidemiological implications.

Co‐occurrence and seasonal and environmental distributions of the sandflies Lutzomyia longipalpis and Nyssomyia whitmani in the city of Puerto Iguazú, northeastern Argentina

“…The explanation for this could be the fact that seasonal dynamics is a complex process resulting from abiotic variables modulating biotic ones. Temperature, rainfall, and RH have previously been studied as possible factors associated with phlebotomine seasonal dynamics (Oliveira et al, 2008, Zeilhofer et al, 2008de Oliveira et al, 2013;de Andrade et al, 2014), as well as photoperiod (Rivas et al, 2014). However, climatic variables not only have effects on current activity and therefore the success of trapping, but also have delayed effects mediated by breeding site availability and population size-cohort progression (Salomón et al, 2004).…”

“…Lutzomyia longipalpis and Ny. whitmani show spatial and temporal variations in their abundances (Brandão-Filho et al, 2011;Donalisio et al, 2012;Fernández et al, 2012Fernández et al, , 2013, and there are also studies of the distribution of these species at the village/city spatial scale (Oliveira et al, 2008;de Souza et al, 2014). However, studies simultaneously examining the seasonal−village abundance distributions of both species, with a focus on TL/VL, are scarce.…”

Leishmaniose visceral e sua relação com fatores climáticos e ambientais no Estado do Tocantins, Brasil, 2007 a 2014

“…Além disso, o aumento da temperatura também aumenta a densidade de flebotomíneos adultos e, por sua vez, o contato entre vetor e hospedeiros e consequentemente a disseminação da doença 16,17 . Corroborando isso, a temperatura pode aumentar a atividade dos flebotomíneos 18 , e repastos sanguíneos repetidos elevam a carga parasitária no vetor 19 , aumentando, dessa forma, a infectividade dos flebotomíneos.…”

“…Ao que parece, não seriam nem temperaturas muito elevadas e nem tão baixas, associadas à ocorrência da LV neste estado 26 , pois assim como se cita a relação da temperatura com a reprodução do parasito, esta também influencia a atividade vetorial. A L. longipalpis apresenta tendência a ser mais ativa à noite, em temperatura de 30ºC 18 , que coincide com as baixas temperaturas diurnas identificadas neste estudo. Os flebotomíneos são vulneráveis a mudanças bruscas de temperatura e, geralmente, preferem regiões nas quais ocorre baixa variação entre as temperaturas mínimas e máximas, visto que sua sobrevivência pode ser reduzida se o clima ficar muito quente e seco 16,27 e, dessa maneira, temperaturas altas diminuem também os casos de LV humana 26 .…”

Effects of El Niño-Southern Oscillation on human visceral leishmaniasis in the Brazilian State of Mato Grosso do Sul

“…Thus, the exposure of individuals -hosts and reservoir -to the vectors can be increased. Rivas et al (23) showed that at 30ºC, the maximum peak of the abundance of Lu. longipalpis was considered lower than the other lower temperature regimes (20ºC and 25ºC).…”