| dc.description | Background: Insect 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.
Methods: We 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).
Results: L. 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.
Conclusions: Herein, 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. | |
