Circadian entrainment by light and host in the haematophagous Chagas vector, Triatoma infestans.

VALENTINUZZI VS; AMELOTTI I, VALENTINUZZI VS, LAZZARI C, CATALÁ S Y D GORLA; GORLA DE; CATALA SS; RALPH MR

Florida

Congreso; Society for Research in Biological Rhythms- SRBR; 2012

SRBR

Triatoma infestans (kissing bug) is the main insect vector of Chagas Disease, a chronic and usually fatal trypanosomiasis. In June, 2011 there were an estimated 80,000-120,000 chronic cases in the United States and between 7-8 million world wide (confirmed cases only), mainly in South America. The haematophagous bug feeds on various diurnal and nocturnal species during the host?s quiescent time. Moreover, the same hosts are also major predators of the bug. We hypothesized that in response to dual selective pressures (temporal patterns of food availability and predation) related to multiple hosts, T. infestans would exhibit flexible circadian responses that would allow it to entrain rapidly to a potential host as a Zeitgeber so that feeding activity is coincident with the inactive period of the host. We used rocking actigraphs to record locomotor patterns of kissing bugs under three conditions: 24h photic entrainment (LD12:12); constant dark (DD); and DD with a daily nonphotic stimulus. Animals entrained to LD cycles with unimodal bouts of activity concentrated during the dark phase. Free-running periods in DD following LD entrainment were longer than 24h (27.08 ± 0.36 h). Sporadic phase shifts in DD were associated with bouts of extended activity. Bugs exhibited a positive phase angle of entrainment to LD (y = 2.8 ± 0.6h), with nocturnal onsets heavily masked by light in the late subjective day. Nonphotic stimuli (proximity of a live chicken, mechanical disturbance) also produced entrainment. Two stable phase angles of entrainment were established such that the stimulus either preceded activity onset (y = -2.2 ± 0.5h) or occurred at the end of the bugs´ activity (y = +9.1 ± 1.1h).  While responsive to light and dark, T. infestans is also highly sensitive to disturbances and other signals that might indicate the presence of a potential host. In nature, this combination would provide this parasite with great flexibility in organizing physiology and behavior in anticipation of a quiescent host, implying a more easily accessible food source with reduced predation risk.