A white eye color mutant in the tsetse fly Glossina morsitans submotsitans Newstead (Diptera: Glossinidae).

A spontaneous mutation in Glossina morsitans submorsitans Newstead is described. The mutant, designated wht, has white compound eyes but the ocelli and testes have normal coloration. Mutants have lower than normal amounts of xanthommatin and pteridines in their heads. The lesion occurs late in the tryptophan to xanthommatin pathway, in the storage of xanthommatin in the compound eyes, or, most likely, in the transport of precursors into the compound eyes. The locus wht is on the X chromosome.     

Experiments on the elimination of symbionts from the tsetse fly,Glossina morsitans morsitans (Diptera: Glossinidae), by antibiotics and lysozyme

One sulfonamide and ten antibiotics were tested for symbiont elimination in Glossina morsitans morsitans. Only tetracycline, penicillin, and kanamycin could be used in concentrations which destroyed the symbionts and impeded host reproduction, but did not affect host longevity. The later the treatment with penicillin and kanamycin began, the smaller was the damage to symbionts from these two antibiotics. Small doses damaged the symbionts to an extent that flies could produce offspring, but these were free of symbionts. Lysozyme was used as an alternative to antibiotics. After both injection and oral administration of lysozyme the symbionts were damaged, and host reproduction ceased, although host longevity remained unaffected. It can be concluded from the results of these experiments that tsetse flies do not require their symbionts for survival but probably do need them for reproduction.     

Does reproductive investment change with age in tsetse flies, Glossina morsitans morsitans (Diptera: Glossinidae)?

1. Viviparous insects such as tsetse ( Glossina spp.) provide unusual opportunities to compare age-related changes in the proportion of maternal resources transferred to offspring.
2. In laboratory populations of Glossina morsitans morsitans the survival of females was high for the first 60 days of adult life but declined rapidly thereafter.
3. Average longevity did not differ significantly between mated and unmated females (93·6 and 90 days, respectively).
4. Nutritional state in terms of fat content and residual dry mass did not decline with adult female age.
5. The fecundity of mated females was constant for the first 60 days of adult life and declined only slightly thereafter.
6. Offspring size did not change towards the end of the adult female lifespan and there was no evidence of an increase in the allocation of resources to reproduction in older females.
7. Results contrast with those obtained recently for vertebrates and may indicate that age-related changes in offspring size in Glossina are not adaptive, or that so few females reach old age under natural conditions that there is no selection for a strategy of terminal investment.     

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.     

Macrogeographic population structure of the tsetse fly, Glossina pallidipes (Diptera: Glossinidae)

Tsetse flies are confined to sub-Saharan Africa where they occupy discontinuous habitats. In anticipation of area-wide control programmes, estimates of gene flow among tsetse populations are necessary. Genetic diversities were partitioned at eight microsatellite loci and five mitochondrial loci in 21 Glossina pallidipes Austin populations. At microsatellite loci, Nei's unbiased gene diversity averaged over loci was 0.659 and the total number of alleles was 214, only four of which were shared among all populations. The mean number of alleles per locus was 26.8. Random mating was observed within but not among populations (fixation index FST=0.18) and 81% of the genetic variance was within populations. Thirty-nine mitochondrial variants were detected. Mitochondrial diversities in populations varied from 0 to 0.85 and averaged 0.42, and FST=0.51. High levels of genetic differentiation were characteristic, extending even to subpopulations separated by tens and hundreds of kilometres, and indicating low rates of gene flow.     

Characterization of microsatellite markers in the tsetse fly, Glossina pallidipes (Diptera: Glossinidae)

Glossina pallidipes is a vector of African trypanosomiasis. Here we characterize eight new polymorphic microsatellite loci in 288 G. pallidipes sampled from 12 Kenya populations. The number of alleles per locus ranged from four to 36 with a mean of 20.5 +/- 10.1. Expected single locus heterozygosities varied from 0.044 to 0.829. Heterozygosity averaged 0.616 +/- 0.246. No linkage disequilibrium was found. We also report results in eight other tsetse species estimated by using the primers developed in G. pallidipes. The primers worked best in G. swynnertoni and G. austeni and worst in G. m. morsitans and G. m. submorsitans.     

Persistent courtship reduces male and female longevity in captive tsetse flies Glossina morsitans morsitans Westwood (Diptera: Glossinidae)

Where males can increase their mating success by harassing femalesuntil they accept copulation, harassing tactics can be expectedto evolve to a point where they have costs to the longevityof both sexes. By experimentally manipulating the sex ratioin captive groups of tsetse flies Glossina morsitans morsitans,we demonstrated that the longevity of females declines wheresex ratios are biased toward males, while the longevity of malesdeclines where the sex ratio is biased toward females. Neitherirradiation of males nor prevention of copulation by blockingor damaging the external male genitalia increased the longevityof females caged with them, suggesting that female longevitywas reduced by the physical aspects of male harassment ratherthan by components of the ejaculate     

Mark-recapture and Moran curve estimates of the survival probabilities of an island population of tsetse flies Glossina morsitans morsitans (Diptera: Glossinidae)

A study on populations of Glossina morsitans morsitans Westwood on Antelope Island, Lake Kariba, Zimbabwe provided Jolly-Seber (J-S) mark-recapture estimates of adult survival and Moran curve estimates of the overall survival of all developmental stages. For females, Moran survival estimates derived using ox fly-round catches showed similar trends to, but were more variable than, those calculated from J-S population estimates. Regression of one set on the other removed only 26% of the variance. Undue emphasis should not be placed on small changes in Moran survival estimates based on sequences of catches. Catch data cannot provide Moran estimates of male survival probabilities and no comparison is thus possible with estimates from the J-S data. The J-S and the Moran approaches were combined to estimate survival probabilities of the immature stages of male and female tsetse. The overall survival per three-week period averaged 45% for males and 59% for females, comprising mature adult survivals of 27 and 46%, and pooled survivals of immature stages of 59 and 77%, respectively. The high survival of immature flies is due to the sheltered, inactive nature of pupal life. Adult and overall survival probabilities were highly correlated in males (r(2) = 0.61) but less so in females (r(2) = 0.24) where capture rates were lower and variance in the results greater. Immature and overall survival was more highly correlated for both sexes, with r(2) = 0.77 and 0.53 for males and females respectively. When a fixed pupal mortality of 1% per day was assumed, estimates of the survival of young adult males suggested that these were even lower than the survival of mature flies at the harshest times of the year, but were not markedly different when overall survival was high. Assuming equal mortality in all adults enabled the estimation of pupal survival. These had high variances but there was no evidence of any difference between the survival probabilities of male and female pupae.     

Identification and properties of microsatellite markers in tsetse flies Glossina morsitans sensu lato (Diptera: Glossinidae)

Genomic libraries enriched for simple sequence repeats were constructed for Glossina morsitans morsitans, G. m. submorsitans, and G. m. centralis. Sixteen microsatellite markers were isolated from the libraries and evaluated on flies from natural G. m. morsitans populations and other Glossina species in the Morsitans and Palpalis species groups. The primers amplified appropriate sized DNA fragments in the Morsitans and Palpalis groups. In G. morsitans s.l., eight of 12 dinucleotide repeats and four of 12 trinucleotide repeats were polymorphic. The polymorphic loci showed a mean 7.5 +/- 4.8 alleles per locus and their mean heterozygosity was 55.8 +/- 7.7%.     

Octopamine distribution in the tsetse fly Glossina morsitans

Tissues of Glossina morsitans were assayed for octopamine using an enzymatic technique. Octopamine was detected at the highest concentration in the brain (7.06-7.99 ng mg-1 tissue protein) and thoracic ganglion (10.9-13.89 ng mg-1 tissue protein). Octopamine was present in haemolymph at a concentration of 1.0-1.27 X 10(-7) M. This was not found to vary when insects were flown or mechanically stressed. Nervous tissue, flight muscle and haemolymph showed a significant ability to metabolize octopamine. The greatest enzyme activity was present in the haemolymph.     

Population genetics of Glossina morsitans submorsitans (Diptera: Glossinidae)

Breeding structure of Glossina morsitans submorsitans Newstead was evaluated by using genetic markers in mitochondrial DNA where diversity was scored at two loci in five natural populations from The Gambia and two populations in Ethiopia (form ugandensis Vanderplank), countries separated by c. 5450 km. Twenty six haplotype combinations were found, of which 17 were shared among two or more populations. Nine haplotypes were found in The Gambia and 23 haplotypes in Ethiopia. There were 12 unique haplotypes. Only six haplotypes were shared between the two countries. Populations in The Gambia (he = 0.26 +/- 0.04) showed less than a third of the diversity of populations in Ethiopia (he = 0.84 +/- 0.03). This suggests recovery from an earlier reduction in population. In a nested analysis of molecular variance of haplotype frequencies, 65% of the variance was due to differences within populations, 34% to differences between populations grouped by country, and only 1% was due to differences among populations within countries. In terms of gene flow, the fixation index FST = 0.35, which leads to an estimate by Wright's island model of less than one reproducing migrant per generation exchanged between the eastern and western submorsitans populations. Nei's genetic similarity measure showed a deep division between Gambian and Ethiopian populations.     

Maturation of the tsetse fly Glossina pallidipes (Diptera: Glossinidae) in relation to trap-orientated behaviour

ABSTRACT The fat free dry weight or residual dry weight of the thorax (Trdw) increased linearly for the first 10 days of adult life in both sexes of G.pallidipes in the laboratory as their flight muscles developed. Using ovarian dissection to estimate the ages of nulliparous adult females of G.pallidipes , the Trdw was also found to increase linearly for at least 14 days in the field. Significant increases in pteridine fluorescence with age were measured in both laboratory-reared males and females of known chronological age and in wild-caught nulliparous females whose ages were estimated by ovarian dissection. A linear relationship existed between pteridine fluorescence and wing fray category for a wide range of ages of field-caught flies of both sexes. A stationary trap baited with ox odour was selective in that only the hungrier portion of the flies attracted to it actually entered. However, it was not selective in terms of the mean ages of flies caught. Comparisons were made of the age compositions of catches of both sexes of G.pallidipes attracted to a stationary trap baited with synthetic odours or to a mobile electrified net by plotting Trdw values against pteridine fluorescence. Nulliparous females were not attracted to the stationary trap, but were attracted to the mobile bait. Males of all ages appeared to be equally attracted to both. It is concluded that nulliparous females do not respond to host odour stimuli until they are ready to mate, perhaps relying on the energy-conserving strategy of watching for a moving host animal before attempting to feed. Alternatively, synthetic odours may differ from natural host odours in terms of their attractiveness to young females. Males, however, probably exhibit dual sexual and feeding behaviour by responding to an odour-baited stationary trap even when young.     

Genetics of Glossina morsitans morsitans (Diptera: Glossinidae). X. A mutant (sabr) having long scutellar apical bristles in females

A line of Glossina morsitans morsitans Westwood was established in which females have scutellar apical bristles approximately three times as long as normal. In other respects the flies appear normal. The mutant allele, sabr, is recessive to the wild-type allele. The locus for sabr is located in linkage group III, 50 or more map units from the locus for malic dehydrogenase. Scutellar apical bristles in mutant flies are longer in flies emerging from puparia maintained at 30 degrees C than in flies emerging from puparia maintained at 25 degrees C.