Tsetse Fly Glossina Morsitans Research Articles

Field experiments on a new method for determining age in tsetse flies (Diptera: Glossinidae)

ABSTRACT. Data are presented which suggests that the accurate determination of the age of tsetse flies (Glossina morsitans morsitans Westwood and G. pallidipes Austen) in the field can be achieved by measuring the fluorescence content of the head capsule. The way in which this can be achieved and further work which would improve the accuracy of the technique are discussed.

Evolution of the secondary structures and compensatory mutations of the ribosomal RNAs of Drosophila melanogaster.

This paper examines the effects of DNA sequence evolution on RNA secondary structures and compensatory mutations. Models of the secondary structures of Drosophila melanogaster 18S ribosomal RNA (rRNA) and of the complex between 2S, 5.8S, and 28S rRNAs have been drawn on the basis of comparative and energetic criteria. The overall AU richness of the D. melanogaster rRNAs allows the resolution of some ambiguities in the structures of both large rRNAs. Comparison of the sequence of expansion segment V2 in D. melanogaster 18S rRNA with the same region in three other Drosophila species and the tsetse fly (Glossina morsitans morsitans) allows us to distinguish between two models for the secondary structure of this region. The secondary structures of the expansion segments of D. melanogaster 28S rRNA conform to a general pattern for all eukaryotes, despite having highly divergent sequences between D. melanogaster and vertebrates. The 70 novel compensatory mutations identified in the 28S rRNA show a strong (70%) bias toward A-U base pairs, suggesting that a process of biased mutation and/or biased fixation of A and T point mutations or AT-rich slippage-generated motifs has occurred during the evolution of D. melanogaster rDNA. This process has not occurred throughout the D. melanogaster genome. The processes by which compensatory pairs of mutations are generated and spread are discussed, and a model is suggested by which a second mutation is more likely to occur in a unit with a first mutation as such a unit begins to spread through the family and concomitantly through the population. Alternatively, mechanisms of proofreading in stem-loop structures at the DNA level, or between RNA and DNA, might be involved. The apparent tolerance of noncompensatory mutations in some stems which are otherwise strongly supported by comparative criteria within D. melanogaster 28S rRNA must be borne in mind when compensatory mutations are used as a criterion in secondary-structure modeling. Noncompensatory mutation may extend to the production of unstable structures where a stem is stabilized by RNA-protein or additional RNA-RNA interactions in the mature ribosome. Of motifs suggested to be involved in rRNA processing, one (CGAAAG) is strongly overrepresented in the 28S rRNA sequence. The data are discussed both in the context of the forces involved with the evolution of multigene families and in the context of molecular coevolution in the rDNA family in particular.

Proline synthesis in the fat body of the tsetse fly Glossina morsitans, and its stimulation by isocitrate

The in vitro synthesis of proline from glutamate was followed in fat body homogenates from the tsetse fly Glossina morsitans. Rates of synthesis were much higher in freeze-thawed or sonicated homogenate than in untreated homogenate. Synthesis in the presence of added glutamate was significantly stimulated by addition of NADH, NADPH and ATP, the effects of these coenzymes being approximately additive. Isocitrate stimulated proline production in the presence of glutamate. This effect was most marked when no coenzymes were added, but was observed also when all three coenzymes were present. α-Oxoglutarate was without action. α-Oxoglutarate was produced when freeze-thawed fat body homogenate was incubated with isocitrate. Production was enhanced when glutamate was also present, and enhanced further by the combined addition of NADH, NADPH and ATP. The role of isocitrate in proline synthesis is discussed. It is suggested that synthesis from glutamate utilizes NADPH generated by the oxidation of isocitrate through the mitochondrial NADP-isocitrate dehydrogenase reaction.

Predicted and observed droplet deposition on tsetse flies (Glossina morsitans) following aerosol application from aircraft

AbstractA non‐toxic formulation containing fluorescent tracer was dispersed as an aerosol over savannah woodland in stable meteorological conditions, with only light wind, shortly after sunrise. Droplet deposition on wild caught tsetse flies (Glossina morsitans) was measured by means of a fluorescent tracer technique and compared with the deposit levels predicted from rotary sampler measurements using droplet collection efficiency data for samplers and flies derived from a laboratory wind tunnel study. Good correlation was found between the predicted and observed dose. An additional comparison, based only on rotary sampler data, between a typical spray (measured v.m.d. 27 μm) and a spray with smaller drop size (measured v.m.d. 21 μm) suggested that the latter might be significantly more effective as a means of control.

Comparative study of some expanding arthropod cuticles: The relation between composition, structure and function

The abdominal cuticles of the adult female ticks Argas (Persicargas) robertsi and Boophilus microplus, sp der Badumna insignis, tsetse fly Glossina morsitans morsitans, sheep ked Melophagus ovinus and locust Locusta migratoria migratorioides and of the fifth-instar larva of the bug Rhodnius prolixus stretch greatly, some of them quite rapidly, when they are feeding, laying eggs or carrying a developing larva or egg mass. During this expansion the epicuticle, which is convoluted, unfolds and the underlying endocuticle stretches. There is an increase in the volume of each of the cuticles on expansion. The fine structures of those cuticles which go through cycles of expansion and contraction do not become disrupted. Cuticles with acidic proteins have much higher chitin contents than those with basic proteins. Plasticization, i.e. breaking of intermolecular non-covalent bonds, precedes rapid expansion of cuticles but is unnecessary for slow expansion. The compositions of the cuticles and the properties of the proteins are discussed in relation to the expansions which take place in the cuticles.

Lesions and saliva-specific antibody responses in rabbits with immediate and delayed hypersensitivity reactions to the bites of Glossina morsitans centralis.

Rabbits exposed to feeding tsetse flies developed cutaneous hypersensitivity responses to fly bites. These responses had characteristics of immediate and delayed type hypersensitivity. Saliva components from the tsetse fly Glossina morsitans centralis were electrophoretically separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Major salivary proteins of 160, 92, 66, 64, 55, 42, 33, 28, and 15 kilodaltons were identified. Separated salivary components were transferred to nitrocellulose filters and probed with lectins and with whole sera and purified IgG from rabbits which had been exposed, via fly feeding, to tsetse antigens for variable periods. Many of the salivary proteins were identified as glycoproteins. Several major salivary proteins were recognized by antibodies from sensitized rabbits.

Trypanosoma brucei: Infectivity and immunogenicity of cultured parasites

Trypanosoma brucei brucei, derived from the salivary glands of infected tsetse flies ( Glossina morsitans morsitans) and maintained in culture for over 4 years, were infective to both albino rats and tsetse flies. Virulence was markedly enhanced during the first passage in albino rats or tsetse flies. Irradiated cultured trypanosomes induced immunity to homologous challenge but not to tsetse fly or blood-induced challenge with the same stock.

Induction of systemic and local basophil and eosinophil responses in guinea pigs by the feeding of the tsetse fly Glossina morsitans

Guinea pigs infested with Glossina morsitans weekly for 5 weeks exhibited marked peripheral blood basophil and eosinophil responses to each infestation, with a dominant cutaneous basophil response to challenge infestation. G. morsitans feeding was completed within 3–10 min, depending upon prior exposure, and flies were reluctant to feed and probed longer on hyperexposed animals. Blood basophil responses exhibited the greatest increases over controls (up to 12-fold) compared to eosinophils (up to 3-fold). After the first and third infestations, both basophil and eosinophil levels increased, whereas after the second and fourth infestations both cell types declined. Greatest blood basophil responses developed after the first infestation with levels ranging from 0 to 14 ± 9 cells/mm 3 in infested animals to 0 and 2 ± 2 cells/mm 3 in uninfested controls. Eosinophilia increased with each infestation where levels ranged from 57 ± 23 cells/mm 3 after the first tsetse feeding to 110 ± 20 cells/mm 3 after the fourth infestation; compared to 11 ± 11 to 50 ± 12 cells/mm 3 in uninfested controls. Fly-feeding sites were marked by hemorrhages, and probing behavior resulted in a line of small hemorrhages when the underside of the skin was examined. Histologically, G. morsitans feeding sites in naive guinea pigs 24 h post-infestation were dominated by mononuclear cells (93% of the infiltrate) with a weak granulocyte component, of which eosinophils were dominant (1.3%). Tsetse feeding sites in guinea pigs exposed 3 times previously were again dominated by mononuclear cells (57% of the infiltrate), but granulocytes comprised a significant part of the response (43% of the infiltrate) where basophils were dominant (25%).

Enzyme activities in the fat body of the tsetse fly Glossina morsitans and the fleshfly Sarcophaga tibialis in relation to proline metabolism

Enzymes were assayed in the fat body of the tsetse fly Glossina morsitans and compared with those in the fat body of the fleshfly Sarcophaga tibialis. Alanine aminotransferase, 3-hydroxyacyl-CoA dehydrogenase, NADP-linked isocitrate dehydrogenase and proline synthetase were much more active in G. morsitans. NADP-linked malic enzyme, pyruvate carboxylase, citrate synthase and aconitase were also more active in G. morsitans, but α-oxoglutarate dehydrogenase, fumarase, malate dehydrogenase and various glycolytic enzymes were more active in S. tibialis. Pyruvate carboxylase was mainly mitochondrial in the fat body of both insects, whereas NADP-linked malic enzyme was cytoplasmic. Alanine aminotransferase and NADP-linked isocitrate dehydrogenase were more predominantly mitochondrial in G. morsitans than in S. tibialis. In the fat body of G. morsitans the K m values of pyruvate carboxylase for pyruvate and bicarbonate were quite low, whereas those of NADP-linked malic enzyme were high. Alanine aminotransferase from G. morsitans fat body had lower apparent K m values for alanine and α-oxoglutarate than flight muscle enzyme from the same species. The proline synthesizing potential of G. morsitans fat body is discussed. It is suggested that the pathway involves the enzymes pyruvate carboxylase and NADP-linked isocitrate dehydrogenase.

Infection, immunity and the development of local skin reactions in rabbits infected with cyclically-transmitted stocks of Trypanosoma congolense.

The development of local skin reactions following bites by tsetse flies (Glossina morsitans) infected with Trypanosoma congolense was observed in normal rabbits, in rabbits with concurrent infections with T. congolense and in rabbits challenged after immunization by infection and treatment. Local reactions developed in normal rabbits within seven days of fly bite and were resolved by approximately 19 days after infection. In rabbits with concurrent infections no typical local reactions developed when they were bitten by infected tsetse flies. By allowing a single infected fly to bite a rabbit sequentially it was established that suppression of reaction development to homologous secondary challenge occurred within three to eight days of primary infection. Suppression of reaction development also occurred in infected rabbits challenged with an antigenically heterologous trypanosome stock within 14 to 18 days of primary infection, suggesting that reaction suppression is not associated with the specific immune response. It was also found that no neutralizing antibodies had developed against the parasites used for secondary infection by 28 days post-challenge. Rabbits were immunized by allowing an infected tsetse fly to feed on a rabbit and seven days later, when local reactions had appeared, treating it with homidium chloride. All rabbits challenged within 75 days of immunization by a tsetse fly infected with a homologous trypanosome stock resisted re-infection and some animals were immune up to 300 days after treatment. In most of the immunized animals specific neutralizing antibody activity against homologous parasites was low, suggesting that local expression of immunity in the skin might be more important in resistance to cyclically transmitted infections than serum antibodies. No local reactions developed on immune rabbits challenged with a homologous trypanosome stock but immunized rabbits challenged with heterologous trypanosome stocks developed typical local reactions.

Neuroendocrine stimulation of uterine gland protein synthesis in the tsetse fly, Glossina morsitans

ABSTRACT. The uterine gland of the tsetse fly Glossina morsitans morsitans Westw. synthesizes a secretion which nourishes the developing larva in the uterus. Aqueous extracts of the brain have been shown to stimulate the synthesis of the protein and amino acid components of this secretion from L‐ [U‐14C]leucine by uterine gland tubules in vivo and in vitro. A linear dose response relationship was demonstrated in vitro with extract concentrations ranging from 1 × 10‐4 to 1 × 10‐2 brains μl‐1. The maximum response, a > 300% increase in the rate of protein and amino acid synthesis, was achieved with as little as 1 × 10‐2 brains μl‐1 The concentration of active factor(s) in the brain declined during a single interlarval period coincident with the period of release of secretion associated with larval growth. The stimulatory activity in brain extracts was destroyed by proteolytic enzymes indicating that it is probably a protein or peptide. Results suggest that the active factor(s) is a hormone responsible for the stimulation of uterine gland protein synthesis essential for larval nutrition.

Parturition in the tsetse fly Glossina morsitans: Pattern of activity, sound production and evidence for control by the mother's brain

The mature tsetse larva descends slightly in the uterus causing a protrusion of the female's abdomen and a thrusting open of the female vulva 5–6 h before parturition. Coinciding with larval descent, the female becomes conspicuously restless. The activity pattern monitored by measuring oxygen consumption shows a progression of four discrete stages of activity before and after parturition. Immediately following parturition, the female emits a low frequency sound of 5.8 min duration that differs markedly from sounds produced during feeding or mating. Parturition can be blocked by neck-ligation of the female, thus suggesting a crucial role for the brain. Both neural and hormonal pathways appear to be involved. Transection of the nerve that innervates the uterine muscles reduces the incidence of successful parturition, and parturition in neck-ligated females can be stimulated by transfusion of haemolymph from females that have recently given birth. When parturition is blocked, larvae are retained in utero but eventually pupariate after a delay of 2.3 days.

Effects of a synthetic juvenile hormone mimic on the reproduction of the tsetse fly Glossina morsitans

Topical application of the juvenile hormone mimic 1™75 to pregnant Glossina morsitans 15 or 20 days after emergence resulted in a significant increase in abortions of eggs and larvae of all developmental stages. Small doses (0.25 ng per fly) were sufficient to elicit a response which was more pronounced if application occurred 20 days after emergence. Flies fed once on rabbit ears, which had been treated with 5 ng of the mimic per ear, resulted in abortions and the effect persisted for up to 40 days. The hormone mimic did not induce abortions in isolated pregnant uteri kept in organ cultures for up to 7 days.

Effects of sodium-transport inhibitors on diuresis and mid-gut (Na + + K +)-ATPase in the tsetse fly Glossina morsitans

The effects of four inhibitors of specific sodium-transport mechanisms on diuresis in the tsetse fly Glossina morsitans, have been determined. Ouabain (1.0, 0.1 mM) and ethacrynic acid (1.0, 0.2 mM) reduced the rate of water loss, whereas amiloride (1.0 mM) and furosemide (1.0 mM) did not. The effects of ouabain, ethacrynic acid and meal size upon the anterior mid-gut (Na + + K +)-ATPase activity were also determined. For ouabain, the negative logarithm causing 50% inhibition of (Na + + K +)-ATPase (pI 50) was 6.0, whilst ethacrynic acid together with meal size did not affect the activity of this enzyme. These results show that diuresis in this insect involves the active transport of sodium ions by both electrogenic and Na + K + exchange pumps.

African sleeping sickness: new evidence that mature tsetse flies ( Glossina morsitans) can become potent vectors

Starved mature male tsetse flies (21 to 25 days old) are capable of developing salivary gland (SG) infections of Trypanosoma brucei rhodesiense at rates nearly comparable to teneral males < 24 hours old when given an infective meal containing parasites, horse red cells and culture medium. Although the over-all SG infection rate for mature males starved for three, four or five days before infection was about half that for teneral males < 48 hours old (8 · 0% v. 15 · 6%), males starved for four days developed infection rates (12 · 3%) that were comparable to those of teneral flies < 24 hours old (11 · 8%). It is suggested that the acquisition of infection by mature flies should be considered when evaluating factors contributing either to maintenance of endemic infections or perhaps even epidemic infections of human sleeping sickness.

Changes in the contents of intermediates of proline and carbohydrate metabolism in flight muscle of the tsetse fly Glossina morsit ans and the fleshfly Sarcophaga tibialis

1. 1. The contents of intermediates of proline metabolism, the tricarboxylate cycle and glycolysis were measured over the initial phases of flight in the thorax of the tsetse fly Glossina morsitans and the fleshfly Sarcophaga tibialis. 2. The initial rates of proline loss and alanine increase in G. morsitans were approx. twelve times those found in S. tibialis. 3. In G. morsitans there was a sharp initial decrease in the contents of glutamate, ammonia and citrate. Pyruvate content increased rapidly and those of malate and α-oxoglutarate more slowly. Similar initial changes in the contents of these intermediates were observed in S. tibialis. The total concentration of measured tricarboxylate cycle compounds did not change greatly in either insect when flight commenced. 4. Hexose monophosphate concentrations were much lower in G. morsitans than in S. tibialis, but in both insects an increase in the fructose-1,6-diphosphate/fructose-6-phosphate ratio occurred at the onset of flight. 5. The control of the tricarboxylate cycle and the proline-alanine pathway is considered. The utilisation of proline by S. tibialis during flight is discussed.

Precocene treatment of the female tsetse flyGlossina morsitans morsitans sterilises her female offspring

When adult femaleGlossina morsitans morsitans were treated with either precocene I or precocene II, females of the F1 generation, emerging from pupae of the 2nd, 3rd and 4th reproductive cycles failed to develop oocytes.

Characteristics and implications of knockdown of the tsetse fly Glossina morsitans morsitans westw. by deltamethrin

AbstractLow doses of deltamethrin cause prolonged knockdown of the tsetse fly Glossina morsitans morsitans. Fifty per cent of female flies, treated with the LD15‐(48 h) of deltamethrin, failed to regain their capacity for normal flight for 30 h, compared with 6 h for bioresmethrin and 4 h for permethtin at the equivalent dose. Recovery after exposure to tetramethrin occurred within 1 h. The knockdown effect of deltamethrin on males was even more pronounced although, with both sexes, the onset of the effect was delayed for about 3 h. It is suggested that this prolonged knockdown effect of deltamethrin, at extremely low application rates, may make a significant contribution to the effectiveness of the compound against the tsetse fly.

X-Chromosome involvement in male hybrid sterility from Glossina morsitans sub-species crosses

Crosses between sub-species of the tsetse fly Glossina morsitans yield males which can mate but are unable to inseminate. To test the hypothesis of X-chromosome involvement in this form of male sterility, G. m. morsitans carrying the X-chromosome marker ocra were mated to wild type G. m. centralis, and the F1 females backcrossed to each parental population. The ocra gene was used to distinguish those male progeny which had inherited their X-chromosomes from each sub-species and these categories of male from each backcross differed significantly in the proportion which could inseminate. It is concluded that inability to inseminate is caused by an interaction of the X-chromosome from one sub-species with the Y-chromosome and/or autosomal factors from the other. The results are discussed in relation to similar observations from crosses within two Anopheles species complexes and to the genetic control of tsetse flies.

Occurrence of birds in acacia woodland in Northern Botswana related to endosulfan sprayed for tsetse fly control

The occurrence of birds was monitored in Acacia woodland during tsetse fly Glossina morsitans control operations in northern Botswana. These involved sequential applications of endosulfan applied as an ultra-low volume aerosol at rates of 6–12 g ha −1. During the spraying season bird species diversity increased along two sprayed and two unsprayed transects. No species suffered catastropic decline. Changes in the occurrence of insectivorous species were similar along the sprayed and unsprayed transects.