Sensory Ecology. B: Communication

LORENZO FIGUEIRAS, AN; MANRIQUE, GABRIEL; LORENZO, MG; LAZZARI, CR; SCHILMAN, PABLO ERNESTO

Atlas of Chagas’ disease vectors in America

FIOCRUZ

Lugar: Rio de Janeiro; Año: 1999; p. 1089 - 1103

Sensory Ecology deals with informational interaction between organisms, and between them and the environment.  It addresses questions such as what strategies do animals use to locate resources, how information is obtained, and how it is used.  During the last decades, different efforts were made in order to analyse how Chagas´ disease vectors acquire and make use of the information from the environment, other organisms included.  Various aspects of the biology of Triatominae were studied, including habitat selection, host finding, spatial and temporal orientation, as well as intraspecific communication (Schofield, 1979; Zeledón & Rabinovich, 1981; Núñez, 1987).  Follows a brief summary of the present knowledge on some relevant questions.             Habitat selection involves the use of cues for orientation and selection of resting places.  Few data are available on the orientation of bugs to human houses, although light could be involved as a guiding cue during flight (Lehane & Schofield, 1982; Mc Ewen & Lehane, 1993; Insausti & Lazzari, 1996).  Inside houses bugs are not randomly distributed; besides of being found associated to host resting places, they also show active preferences for certain environmental conditions, i.e., temperature and humidity.  On one hand, the selection of a given temperature depends on the daytime, the presence of refuges and the physiological state of the animals (Di Luciano, 1983; Lazzari, 1991a; Lorenzo & Lazzari, 1996).  On the other hand, dry environments are actively chosen in a fixed fashion, i.e., to remain, to oviposit and at the time of ecdysis (Roca & Lazzari, 1994; Lorenzo & Lazzari, 1996).  Some triatomine bugs show a strong preference for staying in physical contact with other individuals and with the substrate, a behaviour named thigmotaxis.  As a consequence, these insects appear assembled inside wall cracks, crevices and other shelters.             Host finding is aided by a diversity of cues, including heat, and chemical substances carried by air currents.  Wigglesworth & Gillet (1934) showed that Rhodnius prolixus orientates using heat as a cue, and suggested that the antennae of this bug are involved in its reception.  The body heat radiation, of wavelengths in the infrared region, is perceived and exploited for orientation by Triatoma infestans (Lazzari & Núñez, 1989; Flores & Lazzari, 1996).  This species exhibits the highest thermal sensitivity known in animals at present (Lazzari, 1989).  In relation to chemical cues, odours released by hosts have been shown to attract bugs (Núñez, 1982; 1987; Taneja & Guerin, 1995; 1997).             Intraspecific communication occurs at least through two channels in triatomine bugs, the chemical (pheromones) and the vibratory one (stridulation).  An aggregation signal has been demonstrated to occur in the faeces of many species of this group (Schofield & Patterson, 1977; Lorenzo Figueiras et al., 1994).  In T. infestans, its biological role was shown to be the guidance of the insects to their refuges (Lorenzo & Lazzari, 1996).  In relation with the sexual context, the occurrence of the copula was shown to evoke the aggregation of males around mating pairs both, in R. prolixus and T. infestans (Baldwin et al., 1971; Manrique & Lazzari, 1995; de Brito Sánchez et al., 1995).  Moreover, in the same context, females stridulate to reject the copulatory attempts performed by males (Manrique & Lazzari, 1994; Roces & Manrique, 1996; Schilman & Manrique, 1997).             In this chapter, the existing evidences dealing with the orientation behaviour of triatomines towards different environmental and host related cues are analysed.  Besides, different modalities of communication between triatomines in several contexts are discussed.