Circadian system responses to nocturnal and diurnal hosts in the kissing bug,Triatoma infestans

Abstract

Insects express diverse behavioral rhythms synchronized to environmental cycles. While circadian entrainment to light-dark cycles is ubiquitous in living organisms, synchronization to non-photic cycles may be critical for hematophagous bugs that depend on rhythmic hosts. The purpose was to determine whether Triatoma infestans are capable of synchronizing to the circadian rhythms of potential hosts with temporally distinct activity patterns; and, if so, if this synchronization occurs through masking or entrainment. Precise synchronization with the food source may be critical for the insects' survival due to the specific predatory or defensive nature of each host. Kissing bugs were housed in a compartment in constant dark, air-flow-connected to another compartment with a nocturnal or a diurnal host; both hosts were synchronized to a light-dark cycle. The activity rhythms of kissing bugs were modulated by the daily activity rhythms of the vertebrates. Effects were a decrease in the endogenous circadian period, independent of the host being nocturnal or diurnal; in some cases relative coordination occurred and in others synchronization was clearly achieved. Moreover, splitting and bimodality arose, phenomena that were also affected by the host presence. The results indicate that T. infestans were able to detect the non-photic cycle of their potential hosts, an ability that surely facilitates feeding and hinders predation risk. Understanding triatomines behavior is of fundamental importance to the design of population control methods.

Spatial distribution of synanthropic triatomines in Piaui State, Northeastern Brazil

“…The various species of triatomines occupy specific geographic distributions, defined in part by their natural habitats within different regions and biomes on the American continent [2][3][4][5][6][7] . Distinct species of triatomines transmit T. cruzi with varying efficiency, defined by the insects' behavior, physiology and adaptation to the human domicile [8][9][10][11] . After an intensive utilization of pyrethroid insecticides in endemic areas in Brazil, the transmission of Chagas disease by triatomines (mainly Triatoma infestans) was virtually eliminated in many States 12 .…”

An increased number of individuals of a potential host facilitates non-photic synchronisation in the haematophagous insect Triatoma infestans

“…This high-number rodent result, contrasts with the one-rodent experiment of Lopez et al, 19 where in the latter, insects only showed modulation of their rhythmicity, reinforcing the idea that more rodents may imply in a stronger synchroniser. Domestic triatomine species tend to be more present in rural dwellings with a higher proportion of humans and/or domestic animals (chickens, goats, dogs, etc.)…”

“…Our Lab has a colony in which individual activity is constantly recorded, a fact that strongly facilitated the logistics of the present experiment; (c) In the field, diurnal tuco-tucos 24 share the same habitat with nocturnal T. infestans ; (d) In Lab, fasted kissing bugs have been monitored feeding on tuco-tucos during the light phase (Abrahan L and Tachinardi P, unpublished observations); (e) In the laboratory setup, the daily activity of a single tuco-tuco in close proximity, has been shown to modulate the activity of triatomines. 19 …”

“…Our Lab has a colony in which individual activity is constantly recorded, a fact that strongly facilitated the logistics of the present experiment; (c) In the field, diurnal tuco-tucos (24) share the same habitat with nocturnal T. infestans; (d) In Lab, fasted kissing bugs have been monitored feeding on tuco-tucos during the light phase (Abrahan L and Tachinardi P, unpublished observations); (e) In the laboratory setup, the daily activity of a single tuco-tuco in close proximity, has been shown to modulate the activity of triatomines. (19) Rodents were individually housed in running-wheel cages in the animal room, and their wheel-running activity rhythms were used as the marker of the potential non-photic synchroniser. The activity rhythms of the 24 rodents were clearly synchronised to the natural photoperiod (through a glass window).…”

“…On the other hand, free running rhythms of this same triatomine species was modulated by the daily activity of a single host (nocturnal or diurnal), housed in close proximity. 19 These authors conducted the experiments with the bugs in constant dark, so that the synchronising signals in question were strictly non-photic. Kissing bugs’ typical long period decreased in the presence of either host with some bugs achieving relative coordination.…”