Salivation pattern of Rhodnius prolixus (Reduviidae; Triatominae) in mouse skin
Introduction
Triatomines are paurometabolous insects that are obligatory blood feeders in all stages of the life cycle. Their normal hosts are birds or mammals, although they may also feed on other vertebrates. In addition to producing significant blood loss in their hosts (Schofield, 1981), triatomines are medically important as vectors of the flagellate protozoan Trypanosoma cruzi, causative agent of Chagas’ disease in the Americas (Chagas, 1909).
On introducing the mouthparts in the skin of the host in search of blood, hematophagous arthropods unleash a series of physiological responses related to hemostasis, inflammation and immune response (Ribeiro and Francischetti, 2003).
To allow rapid and efficient feeding, triatomines possess a wide variety of bioactive molecules in the saliva, including anticoagulants (Hellmann and Hawkins, 1964, Hellmann and Hawkins, 1965; Ribeiro et al., 1995; Pereira et al., 1996), vasodilators (Ribeiro et al., 1990, Ribeiro et al., 1993; Ribeiro and Nussenzveig, 1993), antihistamine (Ribeiro and Walker, 1994), sialidase (Amino et al., 1998), sodium channel blocker (Dan et al., 1999), immunosuppressor (Kalvachova et al., 1999), pore former (Amino et al., 2002), complement inhibitor system (Cavalcante et al., 2003) and inhibitors of platelet aggregation induced by collagen (Ribeiro and Garcia, 1981; Noeske-Jungblut et al., 1994), ADP (Ribeiro and Garcia, 1980; Sarkis et al., 1986), arachidonic acid (Ribeiro and Sarkis, 1982), thrombin (Noeske-Jungblut et al., 1995; Francischetti et al., 2000), serotonin, epinephrine and norepinephrine (Andersen et al., 2003).
Although triatomine saliva is important to blood feeding (Ribeiro and Garcia, 1981), the process of salivation is still not well known. Thus, the objective of this work was to study the pattern of salivation of triatomines during feeding on the skin of a vertebrate host.
Section snippets
Mice
Hairless mice (HRS/J) aged 30–40 days, reared in the animal facility care from Department of Parasitology (ICB/UFMG) and with a mean weight of 20 g were used in the study. They were provided with standard rodent chow and water ad libitum. Mice used in the experiments had no prior contact with triatomines.
Insects
Third instar specimens of Rhodnius prolixus (Honduras) and second instars of Triatoma infestans (Bolívia) were used, these having been maintained in colonies in the Department of Parasitology,
Labelling of saliva with vital fluorochromes
Although the exoskeletons of R. prolixus and T. infestans fluoresced 24 h after ingesting small quantities of both acridine orange and fluorescein solution, it was only possible to label the saliva of the R. prolixus effectively with the former (Fig. 1A). Third instar nymphs of R. prolixus that ingested this solution were able to feed on the host and complete their life cycle.
Measurement of pH in saliva and hemolymph
The use of indicator stains in capillaries allowed us to measure the pH of saliva and hemolymph for both triatomine
Discussion
In the present study, the fluorochrome acridine orange was used for the first time to label triatomine saliva. The fact that only the saliva of R. prolixus showed fluorescence can probably be explained by the difference in pH between the saliva (⩽6.0) and the hemolymph (6.5–7.0). Due to the higher pH of the hemolymph, many of the molecules of acridine orange dissolved in it are uncharged and thus cross the cell membranes, diffusing to all regions of the insect body. However, on reaching an acid
Acknowledgements
This study was supported by Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and benefited from international collaboration through the ECLAT network.
References (28)
- et al.
Identification and characterization of a sialidase released by the salivary gland of the hematophagous insect Triatoma infestans
Journal of Biological Chemistry
(1998) - et al.
Trialysin, a novel pore-forming protein from saliva of hematophagous insects activated by limited proteolysis
Journal of Biological Chemistry
(2002) - et al.
Inhibition of hemostasis by a high affinity biogenic amine-binding protein from the saliva of a blood-feeding insect
Journal of Biological Chemistry
(2003) - et al.
Purification, cloning, expression, and mechanism of action of a novel platelet aggregation inhibitor from the salivary gland of the blood-sucking bug, Rhodnius prolixus
Journal of Biological Chemistry
(2000) - et al.
An inhibitor of collagen-induced platelet aggregation from the saliva of Triatoma pallidipennis
Journal of Biological Chemistry
(1994) - et al.
Triabin, a highly potent exosite inhibitor of thrombin
Journal of Biological Chemistry
(1995) - et al.
Anticoagulant activity of Triatoma infestans and Panstrongylus megistus saliva (Hemiptera/Triatominae)
Acta Tropica
(1996) - et al.
The salivary and crop apyrase activity of Rhodnius prolixus
Journal of Insect Physiology
(1980) - et al.
Nitric oxide synthase activity from a hematophagous insect salivary gland
Federation of European Biochemical Societies Letters
(1993) - et al.
Anti-thromboxane activity in Rhodnius prolixus salivary secretion
Journal of Insect Physiology
(1982)
Feeding behaviour of morphologically similar Rhodnius species: influence of mechanical characteristics and salivary function
Journal of Insect Physiology
Chagas disease, triatomine bugs, and blood loss
Lancet
Determination of mosquito bloodmeal pH in situ by ion-selective microelectrode measurement: implications for the regulation of malarial gametogenesis
Parasitology
Anti-complement activity in the saliva of phlebotomine sand flies and other haematophagous insects
Parasitology
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