Glossina Austeni Research Articles

Variation in thickness and protein content of the cuticle of the female of Glossina austeni

AbstractThe thickness and total protein content of the ventral abdominal cuticle of the female tsetse, Glossina austeni, increase during the early part of each pregnancy cycle, reaching a maximum at approximately 2 days after ovulation. They decrease thereafter, and reach a minimum value just before larviposition. Virgin females do not exhibit a cycle of protein content or thickness in the cuticle. Preliminary data on the incorporation of [3H]tyrosine or [3H]leucine into the water‐soluble proteins of the ventral abdominal cuticle at the time of the second larviposition suggest that there is rapid turnover of protein in the cuticle at this time. These observations are consistent with the net storage of protein in the cuticle during the early part of pregnancy cycle followed by a net depletion of that store as the nutritional demands of the rapidly growing larva in utero exceed the capacity of the ingested blood meals to supply them.

Characterization of Trypanosoma congolense serodemes in stocks isolated from cattle introduced onto a ranch in Kilifi, Kenya.

A herd of 20 cattle was introduced on a ranch in Kilifi, Coast Province of Kenya, where they were in contact with Glossina austeni for 6 months. In total, 65 trypanosome isolates were made from these animals. Examination of the isolates revealed that 61 were Trypanosoma congolense and 4 were T. theileri. Out of the 61 T. congolense isolates, 55 were successfully passaged and cloned in mice to provide trypanosome populations for further analyses. The stocks and their clones were inoculated into goats on which teneral G. morsitans centralis were later fed in order to provide metacyclics for use in serodeme analysis. Identification of serodemes was carried out by indirect immunofluorescence and neutralization using antimetacyclic hyperimmune sera prepared in mice against metacyclics of cloned trypanosome populations. So far 4 serodemes have been identified in 8 stocks and 7 clones. Each of the 9 stocks contained a mixture of at least 2 of the 4 serodemes identified. Furthermore, stocks isolated sequentially from individual animals contained the same serodemes despite repeated treatment with a curative dose (6 mg/kg body weight) of Berenil between isolations. From the latter finding, it can be inferred that the 4 serodemes were present on the ranch throughout the study period.

Does cuticular elasticity regulate the size of the blood meal imbibed by female Glossina austeni?

In tsetse flies, a larva grows to maturity inside the uterus of the female. The size of the blood meal imbibed by females is known to increase at ovulation and decrease as the larva gets larger, so that the total volume of the fly remains constant. This has led to the hypothesis that meal size is determined by cuticular elasticity. Direct measurement of the elasticity of abdominal cuticle in mated females, before and after ovulation, and in virgin females, which do not ovulate, demonstrates that cuticular elasticity is unrelated to ovulation. Further, meal size is not closely correlated with cuticular elasticity. The hypothesis is therefore rejected.

Sublethal insecticide effects on the probing responsiveness of tsetse flies and blowflies

ABSTRACT. Tethered Glossina austeni Newst. males and females were tested for daily and starvation‐related changes in their probing responsiveness to a warmed sponge surface presented to their tarsi. The change in responsiveness of the two sexes was indistinguishable, both following a marked V‐shape pattern across the photophase of LD 12:12 and an increase from a mean of c. 5% responding on day 3 after a blood‐meal to over 60% doing so on day 6. Sublethal doses (c. LD15) of endosulfan had no detectable effect on this pattern, but of DDT caused a temporary doubling of responsiveness, and of permethrin caused a marked and long‐lasting reduction in responsiveness. Tethered Protophormia terraenovae (R.‐D.) tested similarly for changes in threshold to tarsal stimulation with sucrose solutions (assessed by whether or not they extended the proboscis), showed a marked threshold decrease following LD15 diazinon treatment and, like the tsetse, no effect of LD15 endosulfan treatment, though unlike tsetse they showed no increase in threshold following permethrin treatment. The results are discussed in relation to what is known of the mode of action of these four insecticides, and in relation to circadian rhythm physiology in insects.

Some effects of prolonged virginity on feeding and milk-gland activity in females of the tsetse Glossina austeni (Newst.)

The effects of virginity on feeding and milk-gland (MG) activity were investigated in 4-week-old virgin females of Glossina austeni. The flies take in smaller but constant amount of blood roughly equivalent to their own weight during each feed. This syndrome of feeding to a constant weight with time leads to fatbody hypertrophy largely because of decreased metabolic demands due to the absence of a larva. It is suggested that the small blood-meals of virgin females are probably related to the space limitations in their abdomens, and are probably hormone-mediated, possibly operating via the cuticle. The MG of virgin flies is well-differentiated but the cycles of synthetic activity which the distal MG tubules exhibit in mated flies during a pregnancy cycle are not so apparent in virgins. The secretions of this gland are used to nourish the developing larva and if the MG were very active the secretions produced would be lost. It is concluded that in virgin females the blood-meal is reduced in size, probably as a result, at least partly, of a reduction or absence of neurosecretory out-flow related to mating and ovulation, and the products of their blood-meal apparently are diverted not to the MG but to the fatbody for storage. These effects of virginity on blood-meal size, fatbody and MG activity can be reversed at any time by mating.

The toxicities of some analogues of dieldrin, endosulfan and isobenzan to bloodsucking diptera, especially tsetse flies

AbstractThe dieldrin analogue, 1, 8, 9, 10, 11, 11‐hexachloro‐4, 5‐exo‐epoxy‐2, 3‐7, 6‐endo‐tricyclo‐[6.2.1.02, 7]undec‐9‐ene (HEOM), and the isomeric 3, 4‐exo‐epoxy‐and 3, 6‐endo‐epoxy compounds (HCE and ODA, respectively), incorporating structural modifications of the non‐chlorinated ring system, were tested against adult mosquitoes (mainly Anopheles stephensi List.), tsetse flies (mainly Glossina austeni Newst.) and stable flies, Stomoxys calcitrans (L.). The order of toxicity was ODA > HCE > HEOM. In further tests of residual activity against A. stephensi, ODA was better than HCE but neither was sufficiently persistent to be a promising mosquito toxicant. Analogues of dieldrin (HEOD), endosulfan and isobenzan with reduced numbers of chlorine atoms were tested against G. austeni. In the pentachloro‐analogues of dieldrin and α‐endosulfan, the anti‐bridge chlorine was more important than the syn‐chlorine for toxicity. The general effect of reductive dechlorination was to reduce toxicity, but the effect was small for some endosulfan analogues and in one case there was an increase in toxicity. In the main, toxicities of the endosulfan analogues compared favourably with those of the dieldrin analogues. However, toxicity fell drastically following replacement of the second ethylenic chlorine in isobenzan. The effect of these structural changes on toxicity evidently varied from one series to another and was influenced in an unpredictable manner by the rest of the molecule.

Some Effects of Prolonged Virginity on Feeding and Milk Gland Activity in Females of the Tsetse fly, Glossina Austeni (Newstead)

Some Effects of Prolonged Virginity on Feeding and Milk Gland Activity in Females of the Tsetse fly, Glossina Austeni (Newstead)

The effect of feeding on the cerebral neurosecretory system of the adult male tsetse, Glossina austeni Newst

An analysis of the intensity of staining of the corpus cardiacum and of the neurosecretorty cells of the pars intercerebralis in 3-day-old fed or fasting adult male tsetse has revealed two periods of apparent release of neurosecretion. In fed males, stainable neurosecretion disappears from 14 of the 20 recognizable neurosecretory cells within 10 min of the termination of feeding. There is always less neurosecretory material in the corpora cardiaca of fed males. Secondly, there is an indication of a depletion of material from the cardiaca of both fed and fasted males at about 1700 hours EST.

Some laboratory investigations relevant to the possible use of new pyrethroids in control of mosquitoes and tsetse flies

AbstractCypermethrin, fenvalerate, permethrin, (S)‐α‐cyano‐3‐phenoxybenzyl (1R,cis)‐3‐(2, 2‐dibromovinyl)‐2, 2‐dimethylcyclopropanecarboxylate (NRDC 161) and (R,S)‐α‐cyano‐3‐phenoxybenzyl 2, 2,3, 3‐tetramethylcyclopropanecarboxylate (S‐3206; WL 41706) have been tested against adult mosquitoes (Anopheles stephensi) and tsetse flies (Glossina austeni). They possess many of the necessary characteristics such as high intrinsic toxicity, low volatility, and high stability but vary considerably in the contact action of their spray residues.

Some effects of mating in female tsetse, Glossina austeni Newst.

Virgin females of G. austeni were mated at carefully chosen physiological states to determine the effect of mating on ovulation, neurosecretion and blood meal size. The results suggest that ovulation and larviposition are controlled by neurosecretion, and that the release of neurosecretion requires both a mating stimulus and the presence of a mature egg in one of the ovarioles. The mating stimulus was also found to lead to an increase in blood meal size. Unmated female flies do not ovulate and their mature eggs eventually disintegrate. Virgin blood meal sizes remain relatively low.

Some effects of allatectomy in the female tsetse, Glossina austeni

The effects of juvenile hormone on the milk gland, ovaries, and fat body of adult female G. austeni were studied by allatectomy and hormone replacement therapy. In the absence of juvenile hormone, milk synthesis is slow, leading to the production, in a few cases, of small larvae over a prolonged inter-larval period. In most cases, no viable larva is produced and the fat body hypertrophies. Replacement of the corpus allatum with C 16JH leads to a rapid synthesis of milk, production of normal-sized larvae and a reversal of the effect on the fat body. It is therefore suggested that the milk gland activity is directly influenced by JH. Allatectomy in most cases also results in only one egg being matured. The others do not enter vitellogenesis. Similarly, this effect on the ovaries can be reversed by topical application of C 16JH.

A cytogenetical study of Glossina fuscipes fuscipes including a comparison of the polytene chromosome maps with those of Glossina austeni (Diptera, Glossinidae)

The male meiotic sequence is described for the tsetse fly Glossina fuscipes fuscipes together with the polytene chromosome maps and all principal cytological markers. The diploid chromosome number is 2n=6 and includes a pair of large submetacentric autosomes (L1), a shorter pair of metacentric autosomes (L2), and an X and Y which constitute a heteromorphic pair. Male meiosis is normally achiasmate although evidence is presented which suggests that chiasmata do form in about 1% of males. A detailed comparison between the polytene chromosomes of this species and Glossina austeni indicates that although they must have had a common ancestor, G. austeni is genetically more closely related to morsitans group tsetses.

Diuresis in the tsetse fly Glossina austeni.

After taking a blood meal, the tsetse fly Glossina austeni excretes the excess water and salts of the meal in approximately 30 min. During this period a volume of fluid equivalent to 80% of the unfed weight of the fly passes through the haemolymph, whose composition nevertheless remains almost constant. The fluid excreted has a higher sodium and lower potassium concentration than the haemolymph, indicating that sodium may be the prime mover in urine formation in Glossina.

The control of diuresis in the tsetse fly Glossina austeni: a preliminary investigation of the diuretic hormone.

The rate of secretion of the Malpighian tubules of Glossina austeni is controlled by a diuretic hormone. This hormone is present in the nervous tissue of the fly together with a degradative enzyme that can be activated by boiling. It is demonstrated that the Malpighian tubules are able to destroy the diuretic hormone; they may therefore participate in the control of diuresis. The diuretic hormone appears to be a heat-stable, non-dialysable, alcohol-soluble molecule, containing amino acid, glucose and sialic acid residues.

Variations in the amino acids of haemolymph protein in females of Glossina austeni Newst. (Diptera, Glossinidae) during the reproductive cycle

AbstractThe amino acids of the haemolymph proteins of female Glossina austeni Newst. have been analysed at selected times during the first two pregnancy cycles by automatic amino acid analysis. The most prominent amino acids were glutamate, aspartate, lysine and leucine, with these amino acids accounting for almost 50% of the total amino acid residues. The molar percentage of all 16 amino acids observed varied only slightly throughout the pregnancy cycles. The amino acids of the perchloric acid-precipitable fraction of the gut contents of third-instar larvae (considered to be equivalent to milk secretion) have also been analysed and differ considerably from the haemolymph proteins, with glutamate and phenylalanine particularly prominent. Because of their low content of aromatic amino acids, the haemolymph proteins are not regarded as an important store of these compounds.

Synthesis and turnover of haemolymph proteins during the reproductive cycle of Glossina austeni.

The synthesis of haemolymph proteins during the first two pregnancy cycles of the tsetse fly, Glossina austeni, has been investigated by observing the incorporation of 14C-tyrosine and 3H-leucine into the TCA-precipitable fraction. In general, there is a rapid synthesis of haemolymph proteins, with a preferential utilization of 3H-leucine, in newly emerged flies. By the time of the first ovulation, the level of synthesis has dropped, and after this time, there is an apparent preferential incorporation of l4C-tyrosine into haemolymph protein. However, at the first larviposition (L1), there is a rise in incorporation of both amino acids. Haemolymph protein rich in tyrosine has a lower rate of turnover than leucine-rich protein.The percentage incorporation of both 3H-leucine and 14C-tyrosine into haemolymph protein was also determined. At most times during the first-two pregnancy cycles, there is about 2% incorporation. However, in newly emerged flies, the incorporation of 3H-leucine reaches 7%, whereas at L1, about 7% of the 14C-tyrosine is incorporated into haemolymph protein.TCA-soluble label remaining in the haemolymph has been observed during the pregnancy cycles. Whereas 3H-leucine is apparently continuously removed from the haemolymph, 14C-tyrosine, at least at certain stages, may be released into the haemolymph. The significance of these results is discussed in terms of nutrient transfer in Glossina.

Structural and functional dynamics of oogenesis in Glossina austeni: General features, previtellogenesis and nurse cells

Glossina austeni oogenesis throughout its nine-day pregnancy cycle is described with the focus on previtellogenic stages. The ultrastructural details of the oocyte-nurse cell relationship and cyst formation is presented. The oocyte develops in a syncytial association with 15 nurse cells with the entire unit surrounded by a follicular epithelium. The nurse cells have large elaborate nucleoli. Evidence of nuclear emissions and the presence of an unusual cytoplasmic membrane association were found. A variety of nuclear inclusions are seen in the oocyte. Glycogen, lipid, ribosomes and membrane organelles accumulate in the oocyte during previtellogenesis.

Male accessory secretions, their use and replenishment in Glossina (Diptera, Glossinidae)

AbstractThe male accessory glands of Glossina austeni Newst. contain an apical secretion—a dense, opaque, whitish secretion at the apical end of the gland, and a diffuse secretion—a bulkier, more mobile, translucent, whitish secretion occupying nearly all the remainder of the gland. There is also a plug of clear solidified accessory material preventing the outflow of secretions from the resting gland. By immersing the whole accessory gland in a saline medium at pH 2·2, and then transferring the specimen to distilled water, the apical secretion can be separated manually from the rest of the gland, as an apical body. Measurements of the apical body in virgin male flies show that the apical body increases in width according to the equation: Age ≐ constant Χ width 2.5, but individual deviations from this relation were considerable. Immediately after mating the apical body is long and thin; recovery to approximately the resting condition is complete after 48 h, but, on average, mated males have thinner apical bodies than virgin males of the same age. The use of apical secretion measurements to assess mating frequency under field conditions might be possible if adequate samples of males were available.

Changes in the neurosecretory cells, corpus cardiacum and corpus allatum during pregnancy in Glossina austeni Newst. (Diptera, Glossinidae)

AbstractThe neurosecretory cells of the pars intercerebralis, the corpus cardiacum and the corpus allatum were examined in histological sections of Glossina austeni Newst. females fixed at daily intervals over the first two cycles of pregnancy. Two groups of neurosecretory cells corresponding to the lateral and median cells of other insects were recognised. The median neurosecretory cells were found to undergo cyclic changes of net synthesis and net release, which were correlated with ovulation and larviposition. The single ellipsoid corpus allatum undergoes cyclic changes in volume and histological appearance which are correlated with changes in the volume of the milk gland.

Potassium-induced release of the diuretic hormones of Rhodnius prolixus and Glossina austeni: Ca dependence, time course and localization of neurohaemal areas.

ABSTRACT Exposure of neurohaemal areas to solutions of elevated K concentration (above 40 mM) causes a maximal release of diuretic hormone in Rhodnius prolixus and Glossina austeni. An involvement of Ca in hormone release is indicated by the reduction caused by low concentrations of this cation (below 2 mM) or by the presence of Mn. During prolonged treatment with K-rich solutions the rate of hormone release is initially high, but then declines. This response parallels that for Ca entry into squid giant axons during maintained potassium depolarization and suggests that the rate of Ca entry controls the rate of hormone release. Tetrodotoxin did not reduce the potassium-induced release of the hormone, suggesting that K acts directly on the neurosecretory axon endings in the neurohaemal areas.