Salivary gland hyperplasia in wild caught tsetse from Zimbabwe

Hypertrophied salivary glands were collected from wild populations of the tsetse flies Glossina morsitans morsitans Westwood and G. pallidipes Austen in the Zambezi valley, Zimbabwe. Examination of the glands by electron microscopy showed that the associated virus was identical in form in both species. The incidence of salivary gland hypertrophy was significantly higher in G. pallidipes than in G.m.morsitans, and 83% of the enlarged glands of the former were, in addition, found to be infected with Rickettsia-like organisms. There was no indication from this small sample that viral infections predisposed flies to infections with trypanosomes.

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Résumé Des glandes salivaires hypertrophiées ont été extraites de Glossina morsitans et de G. pallidipes provenant de populations sauvages capturées dans la vallée du Zambèze au Zimbabwe. L'examen des glandes au microscope électronique a montré que la forme du virus associé était identique dans les deux espèces. La fréquence d'hypertrophie des glandes salivaires était significativement plus élevée chez G. pallidipes que chez G. morsitans et la fréquence des glandes hypertrophiées de G. pallidides contaminèes par des organismes ressemblant à des Rickettsia était de 0,02. Rien n'indique à partir de ce petit échantillon que la contamination virale favorise l'infection par des trypanosomes.

     

The response of tsetse flies to artificial baits in relation to age, nutritional and reproductive state

In various vegetation types in Zimbabwe, the catches of Glossina pallidipes Austen and G. morsitans morsitans Westw. (Diptera: Glossinidae) at a target baited with odour (acetone, 1-octen-3-ol and two phenols) were positively correlated with catches of the same species at an unbaited net. No correlation existed between target catches and hand net catches of tsetse flies sitting on the vegetation. G. pallidipes females caught at a target and at an unbaited net were older than those caught from vegetation. Of the female G. pallidipes caught at the target, 46% were in the first 3 days of pregnancy. Of those caught at the unbaited net, significantly fewer, 21%, were in this stage. G. pallidipes males caught from vegetation contained more fat (3.07±0.333 mg) than those caught at the unbaited net (2.06±0.339 mg) or at the target (2.19±0.218 mg). It is inferred that target catches consisted predominantly of tsetse which were already in flight when they sensed the stimuli from the target, and that target catches were biased towards female G. pallidipes in the first 3 days of pregnancy.     

Age‐specific changes in sperm levels among female tsetse (Glossina spp.) with a model for the time course of insemination

The age, insemination and ovulation status of tsetse flies Glossina pallidipes Austen (n = 154369) and Glossina morsitans morsitans Westwood (n = 19659), captured over 11 years in Zimbabwe, are assessed by ovarian dissection. Instantaneous rates of insemination increase exponentially with age in both species; 90% insemination levels are reached after 5 days post‐emergence in G. m. morsitans and 7 days in G. pallidipes, varying little with season. More than 95% of both species have ovulated by the age of 8 days and 99% by 12 days. Older flies that have not ovulated are > 100‐fold more likely to be caught in October and November than in other months. A 500‐fold decrease in trap catches did not result in any detectible decrease in the probability of females being inseminated. The proportion of partially filled spermathecae rises for approximately 6 days then declines, consistent with some flies having mated more than once. For flies caught on electric nets, with wings undamaged during capture, wing‐fray data are used to extend ovarian age estimates up to 11 ovulations. Among these flies, the volume of sperm in the spermathecae declines little in flies that have ovulated up to seven times; thereafter, it declines by approximately 1% per ovulation. The time course of insemination and the mating frequency of females are important considerations in modelling tsetse fly populations, as well as for the dynamics of interventions involving the release of genetically‐modified insects, which should not be seriously compromised by the limited levels of polyandry currently observed.     

Seasonal variation of tsetse fly species abundance and prevalence of trypanosomes in the Maasai Steppe,Tanzania

Tsetse flies, the vectors of trypanosomiasis, represent a threat to public health and economy in sub‐Saharan Africa. Despite these concerns, information on temporal and spatial dynamics of tsetse and trypanosomes remain limited and may be a reason that control strategies are less effective. The current study assessed the temporal variation of the relative abundance of tsetse fly species and trypanosome prevalence in relation to climate in the Maasai Steppe of Tanzania in 2014–2015. Tsetse flies were captured using odor‐baited Epsilon traps deployed in ten sites selected through random subsampling of the major vegetation types in the area. Fly species were identified morphologically and trypanosome species classified using PCR. The climate dataset was acquired from the African Flood and Drought Monitor repository. Three species of tsetse flies were identified: G. swynnertoni (70.8%), G. m. morsitans (23.4%), and G.pallidipes (5.8%). All species showed monthly changes in abundance with most of the flies collected in July. The relative abundance of G. m. morsitans and G. swynnertoni was negatively correlated with maximum and minimum temperature, respectively. Three trypanosome species were recorded: T. vivax (82.1%), T. brucei (8.93%), and T. congolense (3.57%). The peak of trypanosome infections in the flies was found in October and was three months after the tsetse abundance peak; prevalence was negatively correlated with tsetse abundance. A strong positive relationship was found between trypanosome prevalence and temperature. In conclusion, we find that trypanosome prevalence is dependent on fly availability, and temperature drives both tsetse fly relative abundance and trypanosome prevalence.     

Polytene chromosome maps in four species of tsetse flies Glossina austeni, G. pallidipes, G. morsitans morsitans and G. m. submorsitans (Diptera: Glossinidae): a comparative analysis

Photographic polytene chromosome maps from pupal trichogen cells of four tsetse species, Glossina austeni, G. pallidipes, G. morsitans morsitans and G. m. submorsitans were constructed and compared. The homology of chromosomal elements between the species was achieved by comparing banding patterns. The telomeric and subtelomeric chromosome regions were found to be identical in all species. The pericentromeric regions were found to be similar in the X chromosome and the left arm of L1 chromosome (L1L) but different in L2 chromosome and the right arm of L1 chromosome (L1R). The L2 chromosome differs by a pericentric inversion that is fixed in the three species, G. pallidipes, G. morsitans morsitans and G. m. submorsitans. Moreover, the two morsitans subspecies appeared to be homosequential and differ only by two paracentric inversions on XL and L2L arm. Although a degree of similarity was observed across the homologous chromosomes in the four species, the relative position of specific chromosome regions was different due to chromosome inversions established during their phylogeny. However, there are regions that show no apparent homology between the species, an observation that may be attributed to the considerable intra—chromosomal rearrangements that have occurred following the species divergence. The results of this comparative analysis support the current phylogenetic relationships of the genus Glossina.     

Glossina morsitans morsitansandGlossina palpalis palpalis:Dosage Compensation Raises Questions about the Milligan Model for Control of Trypanosome Development

Gooding, R. H., and McIntyre, G. S. 1998.Glossina morsitans morsitansandGlossina palpalis palpalis: Dosage compensation raises questions about the Milligan model for control of trypanosome development.Experimental Parasitology90, 244–249. Evidence that dosage compensation occurs in tsetse flies was obtained by comparing the activities of X chromosome-linked enzymes, arginine phosphokinase and glucose-6-phosphate dehydrogenase inGlossina m. morsitansand hexokinase and phosphoglucomutase inGlossina p. palpalis, with the activity of an autosome-linked enzyme, malate dehydrogenase, in each species. The shortcomings of the X chromosome model for the control ofTrypanozoonmaturation in tsetse are discussed in light of these findings and previously published reports on the lack of fitness effects of matureTrypanozooninfections in tsetse and on published results on antitrypanosomal factors in male and female tsetse flies.     

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

ABSTRACT.

• 1 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.
• 2 The way in which this can be achieved and further work which would improve the accuracy of the technique are discussed.

     

Effect of temperature on the reproduction of Glossina pallidipes, with reference to G. m. morsitans

The reproductive biology of G. pallidipes Austen was studied at 28°, 25° and 22° C. Experiments showed that incubation of puparia at 28° C resulted in sterility of both males and females. Incubation at 22° C resulted in a reduced fecundity of the females due to egg retention; the fertility of the males was not affected.Comparative studies with G. m. morsitans Westw. showed that G. m. morsitans puparia are less affected by a temperature of 28° C than are G. pallidipes puparia.

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Effet de la température sur la reproduction de Glossina pallidipes, avec référence à G. m. morsitans

Résumé Les productivités de G. pallidipes Austen élevés au laboratoire pendant tout leur cycle à 22, 25 et 28° C, ont été comparées.A 28° C, la vie intrapupale est réduite à environ 23 jours, contre 30 jours environ à 25° C; la survie des adultes est plus brève qu'à 25° C et les mouches ne s'accouplent pas. Les ovaires présentent une rétention d'oeufs et seulement 1/3 des mâles contient des spermatozoïdes mobiles. A 22° C, le cycle est considérablement prolongé, la vie intrapupale durant environ 40 jours. Les femelles s'accouplaient environ 14 jours après l'émergence. Les ovaires présentaient une rétention d'oeufs, bien que moins souvent qu'à 28° C. Les mâles contenaient des spermatozoïdes mobiles.Des expériences avec changements de température à différents moments du cycle ont montré que la stérilité des mâles et des femelles est provoquée par l'incubation de pupes de G. pallidipes à 28° C. La mensuration des ovocytes montre à 28° C un effet nocif sur leur maturation. Des observations sur les testicules dans les pupes révèlent, par comparaison avec 25° C, que l'enroulement des testicules et des spermatozoïdes est retardé à 28° C, tandis que la pigmentation des testicules est retardée à 22° C. Les pupes de G. m. morsitans sont moins affectées à 28° C que celles de G. pallidipes.

     

Do tsetse flies ‘see’ zebras? A field study of the visual response of tsetse to striped targets

Abstract A field study in Zimbabwe of Glossina pallidipes Austen and G. morsitans morsitans Westwood supported Waage's (1981) hypothesis that the striped pattern of zebras may protect them from being bitten by blood-sucking flies. In addition, the results suggest that the orientation of the stripes may be crucially important for the unattractiveness of zebras. The relative attractiveness of five different stationary targets (black, white, grey, vertically-striped and horizontally-striped; stripe width = 5 cm) were each tested on their own and in pairs of all combinations, with artificial host odour (CO₂ plus acetone) always present. Electric nets were used to catch flies as they attempted to land on or circle the targets. The results were similar for the two species of tsetse. When tested on their own, grey and vertically-striped targets caught similar numbers of flies and both caught significantly fewer than black or white targets (c. 36% as many). Horizontally-striped targets caught <10% as many flies as any other single target. Although there was no significant difference between the attractiveness of grey and vertically striped targets when they were presented together, when paired with the other targets, grey was as attractive as black or white, but the vertically-striped target was significantly less attractive than black or white (P < 0.001). In other words, a difference between grey and vertical stripes was found only in their attractiveness in relation to other targets. The horizontally-striped target, however, always caught the fewest flies, regardless of whether it was presented alone or alongside another target.     

Odorant and Gustatory Receptors in the Tsetse Fly Glossina morsitans morsitans

Tsetse flies use olfactory and gustatory responses, through odorant and gustatory receptors (ORs and GRs), to interact with their environment. Glossina morsitans morsitans genome ORs and GRs were annotated using homologs of these genes in Drosophila melanogaster and an ab initio approach based on OR and GR specific motifs in G. m. morsitans gene models coupled to gene ontology (GO). Phylogenetic relationships among the ORs or GRs and the homologs were determined using Maximum Likelihood estimates. Relative expression levels among the G. m. morsitans ORs or GRs were established using RNA-seq data derived from adult female fly. Overall, 46 and 14 putative G. m. morsitans ORs and GRs respectively were recovered. These were reduced by 12 and 59 ORs and GRs respectively compared to D. melanogaster. Six of the ORs were homologous to a single D. melanogaster OR (DmOr67d) associated with mating deterrence in females. Sweet taste GRs, present in all the other Diptera, were not recovered in G. m. morsitans. The GRs associated with detection of CO₂ were conserved in G. m. morsitans relative to D. melanogaster. RNA-sequence data analysis revealed expression of GmmOR15 locus represented over 90% of expression profiles for the ORs. The G. m. morsitans ORs or GRs were phylogenetically closer to those in D. melanogaster than to other insects assessed. We found the chemoreceptor repertoire in G. m. morsitans smaller than other Diptera, and we postulate that this may be related to the restricted diet of blood-meal for both sexes of tsetse flies. However, the clade of some specific receptors has been expanded, indicative of their potential importance in chemoreception in the tsetse.     

Experimental demonstration of possible cryptic female choice on male tsetse fly genitalia

A possible explanation for one of the most general trends in animal evolution - rapid divergent evolution of animal genitalia - is that male genitalia are used as courtship devices that influence cryptic female choice. But experimental demonstrations of stimulatory effects of male genitalia on female reproductive processes have generally been lacking. Previous studies of female reproductive physiology in the tsetse fly Glossina morsitans suggested that stimulation during copulation triggers ovulation and resistance to remating. In this study we altered the form of two male genital structures that squeeze the female's abdomen rhythmically in G. morsitans centralis and induced, as predicted, cryptic female choice against the male: sperm storage decreased, while female remating increased. Further experiments in which we altered the female sensory abilities at the site contacted by these male structures during copulation, and severely altered or eliminated the stimuli the male received from this portion of his genitalia, suggested that the effects of genital alteration on sperm storage were due to changes in tactile stimuli received by the female, rather than altered male behavior. These data support the hypothesis that sexual selection by cryptic female choice has been responsible for the rapid divergent evolution of male genitalia in Glossina; limitations of this support are discussed. It appears that a complex combination of stimuli trigger female ovulation, sperm storage, and remating, and different stimuli affect different processes in G. morsitans, and that the same processes are controlled differently in G. pallidipes. This puzzling diversity in female triggering mechanisms may be due to the action of sexual selection.     

Characterization of a composite with enhanced attraction to savannah tsetse flies from constituents or analogues of tsetse refractory waterbuck (Kobus defassa) body odor

Savannah tsetse flies avoid flying toward tsetse fly-refractory waterbuck (Kobus defassa) mediated by a repellent blend of volatile compounds in their body odor comprised of δ-octalactone, geranyl acetone, phenols (guaiacol and carvacrol), and homologues of carboxylic acids (C₅-C₁₀) and 2-alkanones (C₈-C₁₃). However, although the blends of carboxylic acids and that of 2-alkanones contributed incrementally to the repellency of the waterbuck odor to savannah tsetse flies, some waterbuck constituents (particularly, nonanoic acid and 2-nonanone) showed significant attractive properties. In another study, increasing the ring size of δ-octalactone from six to seven membered ring changed the activity of the resulting molecule (ε-nonalactone) on the savannah tsetse flies from repellency to attraction. In the present study, we first compared the effect of blending ε-nonalactone, nonanoic acid and 2-nonanone in 1:1 binary and 1:1:1 ternary combination on responses of Glossina pallidipes and Glossina morsitans morsitans tsetse flies in a two-choice wind tunnel. The compounds showed clear synergistic effects in the blends, with the ternary blend demonstrating higher attraction than the binary blends and individual compounds. Our follow up laboratory comparisons of tsetse fly responses to ternary combinations with different relative proportions of the three components showed that the blend in 1:3:2 proportion was most attractive relative to fermented cow urine (FCU) to both tsetse species. In our field experiments at Shimba Hills game reserve in Kenya, where G. pallidipes are dominant, the pattern of tsetse catches we obtained with different proportions of the three compounds were similar to those we observed in the laboratory. Interestingly, the three-component blend in 1:3:2 proportion when released at optimized rate of 13.71mg/h was 235% more attractive to G. pallidipes than a combination of POCA (3-n-Propylphenol, 1-Octen-3-ol, 4-Cresol, and Acetone) and fermented cattle urine (FCU). This constitutes a novel finding with potential for downstream deployment in bait technologies for more effective control of G. pallidipes, G. m. morsitans, and perhaps other savannah tsetse fly species, in ‘pull’ and ‘pull-push’ tactics.     

A model for the relationship between wing fray and chronological and ovarian ages in tsetse (Glossina spp)

Age-dependent mortality changes in haematophagous insects are difficult to measure but are important determinants of population dynamics and vectorial capacity. A Markov process was used to model age-dependent changes in wing fray in tsetse (Glossina spp), calibrated using published mark–recapture data for male G. m. morsitans in Tanzania. The model was applied to female G. m. morsitans, captured in Zimbabwe using a vehicle-mounted electric net and subjected to ovarian dissection and wing fray analysis. Rates of fray increased significantly with age in males but not females, where the rate was constant for ovarian categories 0–3. A jump in mean fray between ovarian categories 3 and 4 + 4n is consistent with the latter category including flies that have ovulated 4, 8, 12, 16 times and so on. The magnitude of the jump could, theoretically, facilitate improved mortality estimates. In practice, although knowledge of fly mortality was required for modelling wing fray, mortality estimates derived from ovarian dissection data are independent of patterns and rates of change in wing fray. Significantly better fits to ovarian age data resulted when age-specific mortality was modelled as the sum of two exponentials, with high mortality in young and old flies, than when mortality was constant at 2.3% per day.     

Effect of antibiotic treatment and gamma-irradiation on cuticular hydrocarbon profiles and mate choice in tsetse flies (Glossina m. morsitans)

Background

Symbiotic microbes represent a driving force of evolutionary innovation by conferring novel ecological traits to their hosts. Many insects are associated with microbial symbionts that contribute to their host’s nutrition, digestion, detoxification, reproduction, immune homeostasis, and defense. In addition, recent studies suggest a microbial involvement in chemical communication and mating behavior, which can ultimately impact reproductive isolation and, hence, speciation. Here we investigated whether a disruption of the microbiota through antibiotic treatment or irradiation affects cuticular hydrocarbon profiles, and possibly mate choice behavior in the tsetse fly, Glossina morsitans morsitans. Four independent experiments that differentially knock down the multiple bacterial symbionts of tsetse flies were conducted by subjecting tsetse flies to ampicillin, tetracycline, or gamma-irradiation and analyzing their cuticular hydrocarbon profiles in comparison to untreated controls by gas chromatography – mass spectrometry. In two of the antibiotic experiments, flies were mass-reared, while individual rearing was done for the third experiment to avoid possible chemical cross-contamination between individual flies.

Results

All three antibiotic experiments yielded significant effects of antibiotic treatment (particularly tetracycline) on cuticular hydrocarbon profiles in both female and male G. m. morsitans, while irradiation itself had no effect on the CHC profiles. Importantly, tetracycline treatment reduced relative amounts of 15,19,23-trimethyl-heptatriacontane, a known compound of the female contact sex pheromone, in two of the three experiments, suggesting a possible implication of microbiota disturbance on mate choice decisions. Concordantly, both female and male flies preferred non-treated over tetracycline-treated flies in direct choice assays.

Conclusions

While we cannot exclude the possibility that antibiotic treatment had a directly detrimental effect on fly vigor as we are unable to recolonize antibiotic treated flies with individual symbiont taxa, our results are consistent with an effect of the microbiota, particularly the obligate nutritional endosymbiont Wigglesworthia, on CHC profiles and mate choice behavior. These findings highlight the importance of considering host-microbiota interactions when studying chemical communication and mate choice in insects.

     

Factors influencing the radiative surface temperature of grey seal (<Emphasis Type="Italic">Halichoerus grypus</Emphasis>) pups during early and late lactation

The aim of this study was to examine the variation in body surface temperature of grey seal (Halichoerus grypus) pups throughout lactation in response to different environmental conditions. Radiative surface temperatures (T _r, °C) of pups were measured on the Isle of May (56°11′N, 02°33′W), southeast Scotland from 29 October to 25 November 2003. Records were obtained from a total of 60 pups (32 female and 28 male) from three different pupping sites during early and late lactation. Pups were sheltered from high wind speeds but air temperature, humidity and solar radiation at pupping sites were similar to general meteorological conditions. The mean T _r of all pups was 15.8°C (range 7.7–29.7°C) at an average air temperature of 10.2°C (range 6.5–13.8°C). There was no difference in the mean T _r of pups between early and late lactation. However, the T _r varied between different regions of the body with hind flippers on average 2–6°C warmer than all other areas measured. There was no difference in mean T _r of male and female pups and pup body mass did not account for the variation in T _r during early or late lactation. Throughout the day there was an increase in the T _r of pups and this explained 20–28% of the variation in T _r depending on stage of lactation. There was no difference in the mean T _r of pups between pupping sites or associated with different substrate types. Wind speed and substrate temperature had no effect on the T _r of pups. However, solar radiation, air temperature and relative humidity accounted for 48% of the variation in mean T _r of pups during early lactation. During late lactation air temperature and solar radiation alone accounted for 43% of the variation in T _r. These results indicate that environmental conditions explain only some of the variation in T _r of grey seal pups in natural conditions. Differences in T _r however indicate that the cost of thermoregulation for pups will vary throughout lactation. Further studies examining intrinsic factors such as blubber thickness and activity levels are necessary before developing reliable biophysical models for grey seals.     

Hytrosavirus genetic diversity and eco-regional spread in Glossina species

Background

The management of the tsetse species Glossina pallidipes (Diptera; Glossinidae) in Africa by the sterile insect technique (SIT) has been hindered by infections of G. pallidipes production colonies with Glossina pallidipes salivary gland hypertrophy virus (GpSGHV; Hytrosaviridae family). This virus can significantly decrease productivity of the G. pallidipes colonies. Here, we used three highly diverged genes and two variable number tandem repeat regions (VNTRs) of the GpSGHV genome to identify the viral haplotypes in seven Glossina species obtained from 29 African locations and determine their phylogenetic relatedness.

Results

GpSGHV was detected in all analysed Glossina species using PCR. The highest GpSGHV prevalence was found in G. pallidipes colonized at FAO/IAEA Insect Pest Control Laboratory (IPCL) that originated from Uganda (100%) and Tanzania (88%), and a lower prevalence in G. morsitans morsitans from Tanzania (58%) and Zimbabwe (20%). Whereas GpSGHV was detected in 25–40% of G. fuscipes fuscipes in eastern Uganda, the virus was not detected in specimens of neighboring western Kenya. Most of the identified 15 haplotypes were restricted to specific Glossina species in distinct locations. Seven haplotypes were found exclusively in G. pallidipes. The reference haplotype H1 (GpSGHV-Uga; Ugandan strain) was the most widely distributed, but was not found in G. swynnertoni GpSGHV. The 15 haplotypes clustered into three distinct phylogenetic clades, the largest contained seven haplotypes, which were detected in six Glossina species. The G. pallidipes-infecting haplotypes H10, H11 and H12 (from Kenya) clustered with H7 (from Ethiopia), which presumably corresponds to the recently sequenced GpSGHV-Eth (Ethiopian) strain. These four haplotypes diverged the most from the reference H1 (GpSGHV-Uga). Haplotypes H1, H5 and H14 formed three main genealogy hubs, potentially representing the ancestors of the 15 haplotypes.

Conclusion

These data identify G. pallidipes as a significant driver for the generation and diversity of GpSGHV variants. This information may provide control guidance when new tsetse colonies are established and hence, for improved management of the virus in tsetse rearing facilities that maintain multiple Glossina species.

     

Proximate causes of sexual size dimorphism in Colorado pikeminnow, a long‐lived cyprinid

Evidence for sexual size dimorphism (SSD) and its possible causes were examined in the endangered Colorado pikeminnow Ptychocheilus lucius, a large, piscivorous, cyprinid endemic to the Colorado River system of North America. Individuals representing 18–24% of the upper Colorado River population were captured, measured, sexed and released in 1999 and 2000. Differing male and female total length‐(L_T) frequency distributions revealed SSD with females having greater mean and maximum sizes than males. Although both sexes exhibit indeterminate post‐maturity growth, growth trajectories differed. The point of trajectory divergence was not established, but slowed male growth might coincide with the onset of maturation. Differing growth rate was the dominant proximate cause of SSD, accounting for an estimated 61% of the observed difference in mean adult L_T. The degree of SSD in adults, however, was also related to two other factors. Evidence suggests males become sexually active at a smaller size and earlier age than females; a 2 year difference, suggested here, accounted for an estimated 12% of the between‐sex difference in mean adult L_T. Temporal shifts in gender‐specific survival accounted for an additional 27% of the observed between‐sex difference in mean adult L_T. Estimated age distributions indicated a higher number of older females than older males and more younger males than younger females in the population during the period of sampling. Dissimilarity of age distributions was an unexpected result because the male : female population sex ratio was 1 : 1 and estimates of long‐term annual survival for adult males and females were equal (88%). Future assessments of SSD in this population are apt to vary depending on the prior history of short‐term gender‐specific survival. Without recognizing SSD, non‐gender‐specific growth curves overestimate mean age of adult females and underestimate mean age of adult males of given L_T. Assuming age 8 years for first reproduction in males and age 10 years for females, the adult male : female ratio was estimated as 1·1 : 1 and mean adult age, or generation time, was estimated as 16·4 years for males and 18·4 years for females.     

Hexamermis glossinae [Nematoda: Mermithidae] parasitizing tsetse [Diptera: Glossinidae] in Kenya

Glossina pallidipes Austen,G. brevipalpis Newstead andG. austeni Newstead were collected from 5 sites along the south Kenyan coast over a 2 year period. They were dissected and examined for nematodes. Three of the sites yielded tsetse parasitized by juvenile mermithids identified asHexamermis glossinae Poinar et al. Glossina pallidipes andG. brevipalpis are new host records for this parasite, whileG. austeni was captured infrequently and only at a site that failed to yield other parasitized tsetse. Parasite prevalence was low (0.16–0.61 %) and did not differ between male and female hosts. More tsetse than expected by chance harboured nematodes during the long rains season (April–August) than during the short rains (September–November) or dry season (December–March). Early juvenile stages (0.5–2.5 mm long) were recovered mainly from tsetse less than 50 days old, while late juvenile stages (35–85 mm long) were only found in flies older than 30 days. Late stages occurred singly while early ones usually occurred as two or more per host.     

Dietary constraints on sexual activity, mating success, and survivorship of male Delia antiqua

The effects of protein-deprivation on the sexual activity and reproductive fitness of male onion flies, Delia antiqua (Meigen) (Diptera: Anthomyiidae), were investigated under laboratory conditions. The percentage of males inseminating gravid females, the magnitude of ovipositional response, and the total numbers of eggs deposited in 1:1 or 1:10 male:female matchings over two days was unaffected by deprivation of dietary protein. The LT₅₀'s (median survival time) for solitary males provided proteinaceous, sucrose, or water diets were 38.0, 25.8, and 6.0 days, respectively. Yet independent of diet effects, males lost 50% of their wing tissue by fragmentation after 26 days, suggesting that wing condition is more important in determining male reproductive fitness than longevity. Male mating frequency in single pairings with previtellogenic females deprived of proteinaceous diet for ten days was similar to that of gravid, protein-fed females. In no-choice and choice mating bioassays at a 10:1 female:male ratio, however, males inseminated significantly fewer previtellogenic than gravid females over 24 h. Despite evidence for male autogeny, removal of exogenous protein resources in the Allium agroecosystem may have important effects on the reproductive competency and fecundity of D. antiqua.     

Olfactory and behavioural responses of tsetse flies, <Emphasis Type="Italic">Glossina</Emphasis> spp., to rumen metabolites

Herbivores provide tsetse flies with a blood meal, and both wild and domesticated ruminants dominate as hosts. As volatile metabolites from the rumen are regularly eructed with rumen gas, these products could serve tsetse flies during host searching. To test this, we first established that the odour of rumen fluid is attractive to hungry Glossina pallidipes in a wind tunnel. We then made antennogram recordings from three tsetse species (G. pallidipes morsitans group, G. fuscipes palpalis group and G. brevipalpis fusca group) coupled to gas chromatographic analysis of rumen fluid odour and of its acidic, mildly acidic and neutral fractions. This shows tsetse flies can detect terpenes, ketones, carboxylic acids, aliphatic aldehydes, sulphides, phenols and indoles from this biological substrate. A mixture of carboxylic acids at a ratio similar to that present in rumen fluid induced behavioural responses from G. pallidipes in the wind tunnel that were moderately better than the solvent control. The similarities in the sensory responses of the tsetse fly species to metabolites from ruminants demonstrated in this study testify to a contribution of habitat exploitation by these vertebrates in the Africa-wide distribution of tsetse.