Lipophorin from the tsetse fly, Glossina morsitans morsitans.

1. Lipophorin was isolated from the haemolymph of adult tsetse fly, Glossina morsitans morsitans, by ultracentrifugation in a potassium bromide density gradient. 2. The tsetse fly lipophorin (Mr congruent to 600,000) has a density of congruent to 1.11 g/ml and consists of two apoproteins, apolipophorin-I (apoLp-I, Mr congruent to 250,000) and apolipophorin-II (apoLp-II, Mr congruent to 80,000), both of which are glycosylated as shown by staining with periodate-Schiff reagent. The protein complex is composed of 49% protein and 51% lipids. 3. The finding of lipophorin in tsetse fly haemolymph suggests that, although these flies primarily utilize proline for their energy needs, there is an active transport mechanism for the supply of lipid requirements.     

Seasonal variations in the distribution and abundance of the tsetse fly,Glossina morsitans morsitans in eastern Zambia

The seasonal changes in the distribution of Glossina morsitans morsitans Westwood (Diptera: Glossinidae) and its main host, cattle, were examined in a cultivated area of the plateau of eastern Zambia. During four consecutive years, the tsetse and cattle populations were monitored along a fly-round transect traversing the two main vegetation types in the study area. These were miombo, a one-storied open woodland with the genera Brachystegia and Julbernardia dominant, and munga, a one- or two-storied woodland where the principal tree genera were Acacia, Combretum and Terminalia. Concurrently, a capture/mark/release/recapture (CMRR) exercise was conducted along two other transects also traversing both vegetation types. The index of apparent abundance of tsetse (IAA) in miombo increased at the beginning of the rainy season (November), reached its peak at the end of the rainy season (April) and was low during the cold season (May to late August), but especially the hot dry season (September to late October). The IAA of tsetse in munga showed a pattern that was the reverse of that in miombo. The seasonal changes in the IAA of tsetse in both vegetation types were in accordance with changes in the movement patterns of tsetse between the two vegetation type as observed using CMRR. The distribution and abundance of cattle along the transect also showed a seasonal trend. This was especially so in munga, during the first three years of observations, where cattle abundance increased gradually from June onwards, reached a maximum at the end of the hot dry season (October-November) and declined steeply at the start of the rainy season (November-December). In both vegetation types, the monthly mean IAA of tsetse was positively correlated with the abundance of cattle in the previous month. It is concluded that the distribution of tsetse in cultivated area of the eastern plateau of Zambia undergoes substantial seasonal changes, which can partly be attributed to changes in the distribution of cattle. The implications of these observations for the control of tsetse are discussed.     

Juvenile hormone mimics as effective sterilants for the tsetse fly Glossina morsitans morsitans

The development of puparia of Glossina morsitans morsitans Westwood was disrupted by topical applications of the juvenile hormone mimics S-methoprene (the resolved enantiomer of 11-methoxy-3,7,11-trimethyl-2,4-dodecadienoic acid 1-methyl ester) (Zoecon), S21149 (propionaldoxime-0-4-phenoxyphenoxyethylether) (Sumitomo), or S31183 (2-[1-methyl-2-(4-phenoxyphenoxy)ethoxy]pyridine) (Sumitomo) dissolved in acetone. Puparia so treated during the first 4 days of life suffered developmental abnormalities, the severity of which were dose-dependent. Similarly, puparia produced by adult females treated with these compounds were abnormal. Dose-response data showed that effects were greatest with S31183 and least with S-methoprene. Abnormalities in the form of abdominal lesions and wing crumpling were typical of flies emerging from puparia produced by S-methoprene-treated females. However, arrested development at the red eye and pigmented seta stage within the puparium were typical of offspring of females treated with S21149 and S31183. A dose of 2 micrograms per female of S31183 was sufficient to prevent emergence of offspring produced for the rest of the life of the fly. The same dose resulted in partial recovery of females treated with S21149 some 18 days following treatment. Treatment with 2 micrograms S-methoprene did not suppress completely the production of normal offspring and recovery was complete some 27-35 days after treatment. Exposure of males to 20 micrograms S31183 did not impair their ability to inseminate females; transfer of material during copulation was sufficient to prevent the production of viable offspring by their mates.(ABSTRACT TRUNCATED AT 250 WORDS)     

A study on isoenzyme polymorphism in the tsetse fly Glossina morsitans

Polymorphism was studied for a number of enzyme systems in the tsetse fly Glossina morsitans. Enzyme polymorphism was observed for -glycerophospate dehydrogenase, aldehyde oxidase and esterases. For esterases, the operation of null alleles was assumed, as otherwise no explanation could be given for the observed frequencies of the variants.Two laboratory colonies and two field populations were compared with respect to their variation at the leucine aminopeptidase (Lap) loci, for which polymorphism was shown to occur in previous work. Conspicuous differences were found between material originating from Tanzania and from Rhodesia. In addition, allelic relationships were established for the Lap ₃-locus.

---

Résumé Faisant suite à des études antérieures, le polymorphisme d'un certain nombre de systèmes enzymatiques a été étudié chez Glossina morsitans. Un polymorphisme a été observé pour l' -glycerophosphate déhydrogénase, pour l'aldéhyde-oxydase et pour les estérases. Pour les estérases, on a supposé l'intervention d'allèles nuls, les fréquences observées chez les variants ne pouvant être expliquées d'autre façon.Deux colonies élevées au laboratoire et deux populations naturelles ont été comparées quant à leur variation au niveau des loci (Lap) pour la leucine aminopeptidase, pour lesquels un travail antérieur avait mis en évidence un polymorphisme. Des différences nettes ont été trouvées entre le matériel provenant de Tanzanie et celui de Rhodésie. En outre des parentés alléliques ont été établies en ce qui concerne le locus Lap ₃.

     

Cloning and expression of the yolk protein of the tsetse fly Glossina morsitans morsitans

Two major families of nutritional proteins exist in insects, namely the vitellogenins and the yolk proteins. While in other insects only vitellogenins are found, cyclorraphan flies only contain yolk proteins. Possible sites of yolk protein synthesis are the fat body and the follicle cells surrounding the oocyte. We report the cloning of the yolk protein of the tsetse fly Glossina morsitans morsitans, a species with adenotrophic viviparity. The tsetse fly yolk protein could be aligned with other dipteran yolk proteins and with some vertebrate lipases. In contrast to the situation in most fly species, only a single yolk protein gene was found in the tsetse fly. Northern blot analysis showed that only the ovarian follicle cells, and not the fat body represents the site of yolk protein synthesis.     

Proline transport by tsetse fly Glossina morsitans flight muscle mitochondria.

1. Proline accumulation by tsetse fly Glossina morsitans flight muscle mitochondria was studied in vitro by the swelling technique and direct measurement of (U-14C) proline. 2. Proline transport was inhibited by the uncharged liposoluble -SH reagent, N-ethylmaleimide but not by ionic reagent, mersalyl, suggesting that the -SH groups involved in the transport of proline are located in a hydrophobic part of the membrane or on the matrix side of the membrane. 3. The kinetic study of proline accumulation revealed saturation kinetics and a high temperature dependence. It gave a Km of 85 microM and a Vmax of 962 pmol/min/mg protein and an activation energy (Ea) of 11 kcal/mol. 4. Certain other amino acids (L-valine, L-alanine, L-methionine, L-phenylalanine, L-tryptophan and L-hydroxyproline) significantly stimulated proline uptake. 5. These observations indicate that tsetse fly Glossina morsitans flight muscle mitochondria contain a proline transport mechanism.     

Oxidation of proline by sarcosomes of the tsetse fly,Glossina morsitans

Mitochondria isolated from the flight muscles of tsetse flies are capable of oxidizing proline at rates commensurate with the requirements of the flight system. The rate of oxidation of other substrates is negligible by comparison. In the presence of phosphate, the oxidation of proline is completely controlled by ADP, acting at the level of the respiratory chain and not at the level of the dehydrogenases. The amount of alanine formed during the in vitro oxidation of ¹⁴C-proline is substantially less than the amount of proline used. The result is interpreted on the basis of a branching of the metabolic pathway at the level of glutamate, with the aminotransferase accounting for approximately 80% of the flux, and glutamic dehydrogenase for the remainder.     

The control of receptivity and ovulation in the tsetse fly, Glossina morsitans

ABSTRACT. A rapid decline in receptivity of mated female Glossina morsitans morsitans Westwood is shown to depend on both physical and chemical stimuli associated with copulation. Radiolabelling revealed the transfer of substances from the male to the haemolymph of the female during copulation. Implantation of male tissues or their injection as homogenates into virgin females showed the chemical stimulus to come from the male accessory glands. Receptivity decreased in females mated to males with ejaculatory ducts severed or testes removed and also in females which had a glass bead inserted into their uterus and/or the tip of their abdomen covered with wax, suggesting that a physical stimulus inducing refractoriness is provided by distension of the uterus and/or stimulation of their terminalial setae. Exposing virgin females to daily short matings in which no male materials were transferred, confirmed this. Receptivity also declined slowly with age in unexposed virgin females. Transfusion of haemolymph from mated females (up to 11 days old) into virgins did not indicate the existence of a haemolymph-borne ovulation-inducing factor; apparently only physical stimuli from mating are involved in the induction of ovulation, and somehow prime the ovarian tissue so that it responds appropriately later when the egg has matured. Whether the stimulus is transmitted to the ovary neurally or hormonally is unknown.     

Wolbachia symbiont infections induce strong cytoplasmic incompatibility in the tsetse fly Glossina morsitans

Tsetse flies are vectors of the protozoan parasite African trypanosomes, which cause sleeping sickness disease in humans and nagana in livestock. Although there are no effective vaccines and efficacious drugs against this parasite, vector reduction methods have been successful in curbing the disease, especially for nagana. Potential vector control methods that do not involve use of chemicals is a genetic modification approach where flies engineered to be parasite resistant are allowed to replace their susceptible natural counterparts, and Sterile Insect technique (SIT) where males sterilized by chemical means are released to suppress female fecundity. The success of genetic modification approaches requires identification of strong drive systems to spread the desirable traits and the efficacy of SIT can be enhanced by identification of natural mating incompatibility. One such drive mechanism results from the cytoplasmic incompatibility (CI) phenomenon induced by the symbiont Wolbachia. CI can also be used to induce natural mating incompatibility between release males and natural populations. Although Wolbachia infections have been reported in tsetse, it has been a challenge to understand their functional biology as attempts to cure tsetse of Wolbachia infections by antibiotic treatment damages the obligate mutualistic symbiont (Wigglesworthia), without which the flies are sterile. Here, we developed aposymbiotic (symbiont-free) and fertile tsetse lines by dietary provisioning of tetracycline supplemented blood meals with yeast extract, which rescues Wigglesworthia-induced sterility. Our results reveal that Wolbachia infections confer strong CI during embryogenesis in Wolbachia-free (Gmm(Apo)) females when mated with Wolbachia-infected (Gmm(Wt)) males. These results are the first demonstration of the biological significance of Wolbachia infections in tsetse. Furthermore, when incorporated into a mathematical model, our results confirm that Wolbachia can be used successfully as a gene driver. This lays the foundation for new disease control methods including a population replacement approach with parasite resistant flies. Alternatively, the availability of males that are reproductively incompatible with natural populations can enhance the efficacy of the ongoing sterile insect technique (SIT) applications by eliminating the need for chemical irradiation.