Behavior of triatomines (Hemiptera, Reduviidae) vectors of Chagas' disease. II. Influence of feeding, lighting and time of day on the number of mating, mating speed and duration of copulation of Panstrongylus megistus (Burm, 1835) under laboratory conditions

To determine in influence of feeding, lighting and time of day on the copulating behavior of Panstrongylus megistus, 480 insect pairs were divided into four groups of 120 each and tested in the following respective situations: without food deprivation (F.D.), with five days of F.D., with ten days of F.D., and with 20 days of F. D. The tests were performed between 9:00 a.m. to 12:00a.m. and 7:00 p.m. to 10:00 p.m., with light (700-1400 lux) and in the dark (1.4-2.8 lux) and behavior was recorded by the time sampling technique. Mating spped (MS) and duration of copulation (DC) were also calculated for each situation. The maximum frequency of copulation was observed after five days of F.D., at night, in the dark (n = 16), and the minimum was observed for recently-fed pairs, at night, with light (n = 4). Males approached females more often than females approached males. MS was lowest in pairs with twenty days of F.D., at night, with light (X = 23.0 ± 16.0 minutes), and highest in recently-fed pairs, during the day, with light (X = 2.9 ± 2.5 minutes). DC was shortest in recently-fed insects, during the day, in the dark (X = 23.5 ± 6.7 minutes), and longest in recently-fed animals, at night, in the dark (X = 38.3 ± 6.9 minutes).

The hemocytes of Panstrogyllus Megistus (Hemiptera: Reduviidae)

Five hemocyte types were identified in the hemolymph of Panstrongylus megistus by phase contrast and common light microscopy using some histochemical methods. These are: Prohemocytes, small cells presenting a great nucleus/cytoplasm ratio; Plasmatocytes, the most numerous hemocytes, are polymorphic cells mainly characterized by a large amount of lysosomes; Granulocytes, hemocytes very similar to plasmatocytes which contain cytoplasmic granules and are especially rich in polysaccharides; Oenocytoids, cells presenting a small nucleus and a thick cytoplasm; they show many small round vacuoles when observed in Giemsa smears and many cytoplasmic granules under phase microscopy; Adipohemocytes, very large hemocytes, presenting many fat droplet inclusions which could correspond to free fat bodies which entered the hemolymph. Only prohemocytes and plasmatocytes can be clearly classified; all the other hemocyte types have a more ambiguous classification.

Midgut of Lepidopteran pupae is a major depot of sequestered, mobilizable, ecdysteroids

Extirpation of endocrine organs - a classic maneuver in hormonal research - has been difficult or impossible in the case of the prothoracic glands (PG) of insects. In larval and pupal Lepidoptera the glands are virtually inaccessible unless one sacrifices the insect. Even then, the PG are not easy to remove in their entirety. Consequently, in order to obtain viable preparations lacking PG, one costomarily makes use of abdomens isolated by litigation or surgery.

Effects of precocene and azadirachtin in Rhodnius prolixus: some data on development and reproduction

The results presented in this paper clearly indicate that precocene and azadirachtin are effective inhibitors of moulting and reproduction in the hemipteran Rhodnius prolixus. The time of application is important and only applications of these substances early in the intermoulting period cause their effects in nymphs. The inhibition of moulting is fully reversed by ecdysone therapy. Precocene and azadirachtin also affected drastically the oogenesis and egg deposition in this insect. Precocene-induced sterilization is reversed by application of juvenile hormone III. However, this hormone is unable to reverse the effect of azadirachtin on reproduction. Ecdysteroid titers in nymphs and adult females are decreased by these treatments. In vitro analysis suggest that precocene and azadirachtin may act directly on the prothoracic glands and ovaries producing ecdysteroids. Based on these and other findings the possible mode of action of these compounds on the development and reproduction of Rhodnius prolixus is discussed.

Vitellogenesis in Manduca sexta

Eggs of Manduca sexta contain four well-characterized protein derived from hemolymph: vitellogenin and lipophorin (very high density lipoproteins); microvitellogenin, a 26,000 dalton female-specific protein lacking lipid and carbohydrate, and insecticyanin, a blue biliprotein composed of four identical 22,000 dalton subunits. In addition, eggs contain a large store of triacyl glycerols. It has been shown that vitellogenin and lipophorin are actively taken up by follicles in vitro. The lipid components of these two proteins together account for only 10% of egg lipid. The follicle actively sequesters intact high density lipophorin, which, inside the oocyte, is stripped of much of its neutral lipid and two molecules of apolipophorin III. On the other hand, low density lipophorin donates diacylglycerol to the oocyte without its protein components being sequestered. Most of the egg lipid is transported from the fat body by a shuttle system involving low density lipophorin.

The cell biology of mosquito vitellogenesis

Insect vitellogenesis involves coordinated activities of the fat body and oocytes. We have studied these activities at the cellular level in the mosquito. During each vitellogenic cycle, the fat body undergoes three successive stages: 1) proliferation of biosynthetic organelles, 2) vitellogenin synthesis, 3) termination of vitellogenin synthesis and degradation of biosynthetic organelles by lysosomes. Analysis with monoclonal antibodies and radiolabelling demonstrated that the mosquito yolk protein consists of two subunits (200-kDa and 65-kDa). Both subunits are glycosylated, their carbohydrate moieties are composed of high-mannose oligosaccharides. The yolk protein subunits are derived from a single 220 kDa precursor detected by an in vitro translation. Oocytes become competent to internalize proteins as a result of juvenile hormone-mediated biogenesis of endocytotic organelles. The yolk protein is then accumulated by receptor-mediated endocytosis. A pathway of the yold protein and factors determining its routing in the oocyte have been studied.

The vitellogenin gene family of Aedes aegypti

We have been interested in identifying genes that play a role in reproduction of the mosquito Aedes aegypti. Our interests are currently focused on the vitellogenin genes which in the mosquito are expressed only in the fat body in response to the insect steroid hormone, 20-hydroxyecdysone. Four of the five vitellogenin genes in the genome have been cloned. We have examined the relationships between these genes and find that they form a small gene family exhibiting different levels of relationship.

Analysis of the interacting components between larval Schistosoma mansoni and schistosome-susceptible and resistant Biomphalaria glabrata

Cell-free hemolymph (serum) and hemocytes from Schistosoma mansoni-susceptible (PR albino M-line) and resistant (10-R2) strains of Biomphalaria glabrata were compared by SDS-PAGE, immunoblotting and radioiodination. Whole serum of both snail strains is dominated by hemoglobin (Hb) (MW = 160 Kd). SDS-PAGE. of Hb-depleted serum indicated that the 10-R2 strain has dominant polypeptides in the 50 to 30 Kd range whereas PR albino snails have few low MW proteins. Antibodies raised to whole PR albino and 10-R2 serum, and the 160 Kd (Hb) band reacted similarly in immunoblot assays. Analysis of hemocytes revealed that 10-R2 snails have a surface-exposed protein at about 80 Kd which is not present on PR albino hemocytes. An examination of primary cultured sporocysts indicated the presence of four major surface proteins (40, 50, 55, 70 Kd) and two minor surface-exposed polypeptides (92, 170 Kd). Antibodies raised against live, intact sporocysts reacted almost exclusively with sporocyst-surface proteins when tested by immunoblotting.

From a mono to a digenetic life-cycle: how was the jump for flagellates of the family trypanosomatidae?

It has been found that species of the digenetic genus Trypanosoma as well as species of monogenetic trypanosomatids of insects can grow in the lumen of the scent glands of opossums reproducing the cycle they perform in the intestinal tract of their insect hosts. Based on these findings, speculations are made on the incompletely known cycles of many mammalian trypanosomes and on the evolution of the family Trypanosomatidae.

Ultrastructural studies of the hemocytes of Panstrongylus megistus (Hemiptera: Reduvidae)

Ultrastructural analyses revealed the presence of six hemocyte types in the hemolymph of Panstrogylus megistus, partially confirming our previous results obtained through light microscopy. Prohemocytes: small, round hemocytes with a thin cytoplasm layer, espcieally rich in free ribosomes and poor in membranous systems. Plasmatocytes: polymorphic cells, whose cytoplasm contains many lysosomes and a well developed rough endoplasmic reticulum (RER).They are extremely phagocytic. Sometimes, they show a large vacuolation. Granulocytes: granular hemocytes whose granules show different degrees of electrondensity. Most of them, have an internal structuration. Coagulocytes: oval or elongated hemocytes, which show pronounced perinuclear cisternae as normally observed in coagulocytes. The cytoplasm is usually electrondense, poor in membranous systems and contains many labile granules. Oenocytoids: large and very stable hemocytes, whose homogeneous cytoplasme is rich in loose ribosomes and poor in membranous systems. Adipohemocytes: large cells, containing several characteristic lipid droplets. The cytoplasm is also rich in glycogen, RER and large mitochondria. The total and differential hemocyte count (THC and DHC) were also calculated for this reduviid. THC increases from 2,900 hemocytes/cubic millimeter of hemolymph in the 4th intar to 4,350 in the 5th and then, decreases to 1,950 in the adults. Plasmatocytes and coagulocytes are the predominant hemocyte types.

Fonte alimentar e potencial vetorial de Triatoma vitticeps (Stal, 1859) com relação à doença de Chagas humana no estado do Espírito Santo, Brasil (Hemiptera, Reduviidae)

In paralel with several other epidemiologic and entomologic data of 19 Municipalities of Espírito Santo State, Brazil, the feeding pattern of 222 Triatoma vitticeps is studied through precipitin tests. Very high levels of natural infection with Trypanosoma cruzi are observed in adult insects, in contrast with the abscence or minimum degrees of infection among nymphs and human individuals. The precipitin tests showed the contact of the insects with multiple blood sources, chiefly human and birds, followed by rodents and marsupials. The data suggest that T. vitticeps in spite of being highly antropophilic, become infected by T. cruzi in sylvatic ambient and occasionally invade houses. The species doesn't seem to be - at least until now - a good vector in the domestic cycle of Chagas' disease. Several factors seem to be involved in this conclusion, mainly the low density of the insect in the houses, its hardness to coloniza them, its slowness concerning to suction and defecation and possibly its low susceptibility to different T. cruzi strains.

Histogical and ultrastructural aspects of the brindley's glands of pantrongylus megistus (Burmeister, 1835) (Hemiptera: Reduviidae)

The Brindley's glands of Panstrongylus megistus were studied under the antomic, histologic and ultrastructural point of view. These glands located in the insect's methatorax are paired and have an opening near the third parir of the feet. Beside this aperture, ther are evaporation areas. Shape, sixe and aspect of the gland vary according to the feeding status. The glands are composed by a tubular part corresponding to the duct and a sack-like portion corrsponding to the secretory part. By electron microscopy we observed that the basal part of the epithelium has many interdigitations associated with mitochondria. On the apical surface where epicuticular foldings are located an electonlucent space is often seen. The glands are composed of the following elements: 1) superficial epithelial cells, located just below the apical surface foldings; 2) secretory cells; which are long and have an intracellular canalicule which changes according to the functional state of the cell; 3) a collecting duct to the secretory cells and covered with an epicuticle, reaching up to the gland's lumen; and 4) cells around the duct.

Estudos bionomicos de Cavernicola lenti Barrett & Arias, 1985 (Hemiptera, Reduviidae, Triatominae)

In the biological study, the development of the biological cycle of the insect under different feeding conditions was evaluated. The insects were fed on either mouse blood (c) or pigeon blood (p) using two types of rearing techniques (individual or group) at 28(graus) C and 90% relative humidity (which is equivalent to their natural environment). A fifth cycle studied, was fed on mouse blood reared on group, and mantained at laboratory environmental temperature. In the five cycles analyzed, it was found that groups on mouse blood at near natural conditions developed more rapidly (between 60 and 73 days) and had a lower rate of mortality (16.66%). The daily handling and changes in environment, of the individually reared insects, for observation of biological characteristics (no. and duration of bloodmeal, defecation and first fed of each stage) had a negative influence. None of the individuals fed on mouse or pigeon blood reached adult hood. It was found that the longevity and the fertility rate were significantly superior on couples maintained individually on mouse blood. These males had an average lifespan of 110,26 days and the females had an average lifespan of 104,46 days. The average number of eggs laid by each female was 21,26. Four couples kept in groups (five couples in each group) under the same condition, the longevity for males was 51,86 days and for females was 81,06 days. An average of 10,5 eggs were laid by each female. However, the percentage of fertile eggs was higher in couples kept in groups (72.15%) than in the individual couples (57.68%).

Trypanosomatid protozoa in fruit of solanaceae in southeastern Brazil

Fruits of cultivated and indigenous Solanaceae from Southeastern Brazil have been examined for the presence of trypanosomatid flagellates. The 14 species found infected were: Capsicum annum, C. praetermissum, Lycopersicon esculentum, Nicandra physaloides, Physalis angulata, Solanum sp., S. americanum, S. concinnum, S. diflorum, S. erianthum, S. gilo, S. robustum, S. variable and S. viarum. The pentatomid hemipteran Arvelius albopunctatus experimentally transmitted flagellates to fruits of some species. Cultures of flagellates were obtained form fruits of eight species of Salonaceae and from A. albopunctatus.

Effects of azadirachtin in Rhodnius prolixus: data and hypotheses

The effects of azadirachtin A, a tetranortriterpenoid from the neem tree Azadirachta indica J., on both development and interaction between Trypanosoma cruzi, the causative agent of Chagas' disease, and its vector Rhodnius prolixus were studied. Given through a blood meal, a dose-rsponse relationship of azadirachtin was established using antifeedant effect and ecdysis inhibition as effective parameters. A singlo dose of azadirachtin A was able to block the onset of mitosis in the epidermis and ecdysteroid titers in the hemnolymph, determined by radioimmuneassay, were too low for an induction of ecadysis. The survival of T. cruzi was also studied in R. prolixus treated with the drug. If the trypomastigotes were fed in presence of azadirachtin A the number of parasites drastically decreased. If the drug was applied after infection of the bug with T. cruzi, the parasite was still abolished from the gut. If the insect was pretreated with azadirachtin A before infection the same observation was obtained. A single dose of azadirachtin A was enough for a permanent resistance of the insect host against its reinfection with T. cruzi and for blocking the ecdysis for a long time. The effects of azadirachtin A on the hormonal balance of the host and growth inhibition of the parasite will be discussed on the basis of the present results.