Darker Flies Research Articles

Survey of conceptual and taxonomic characteristics of the Families Acartophthalmidae, Canacidae and Carnidae (Insecta: Diptera)

The Acartophthalmidae family includes tiny to small dark flies with hyaline or infuscate wings along the coast. Adults live in the forest, where they are associated with decaying substances such as wood, fungi, carrion, excrement and rotten meat. The Canacidae are found along the sea coasts, on the surface of small bodies of water, saline and fresh, in places protected from the wind. They feed on infusoria and other tiny organisms. In Carnidae, the larvae are saprophagous or coprophagous (they live in the litter of birds' nests). Pupae are enclosed within a puparium and bird nests are micro-ecosystems with diverse communities of invertebrates, from ectoparasitoids to commensal species. The objective of this manuscript was to carry out a survey of the Families Acartophthalmidae, Canacidae and Carnidae regarding their biology, ecology, geographic distribution, and taxonomy. The systematized bibliographic study, of the descriptive and exploratory type of the Families Acartophthalmidae and Canacidae. The bibliographic search included the LILACS databases at: http://www.bireme.br/, in electronic journals available at the SciELO and USP databases: http: //www.usp.br/ and in theoretical books, these banks, university dissertations, national and international scientific articles, scientific journals, documents. The main terms used were: Diptera, flies, Acartophthalmidae, Canacidae and Carnidae.

Divergence of larval resource acquisition for water conservation and starvation resistance in Drosophila melanogaster

Laboratory selection experiments have evidenced storage of energy metabolites in adult flies of desiccation and starvation resistant strains of D. melanogaster but resource acquisition during larval stages has received lesser attention. For wild populations of D. melanogaster, it is not clear whether larvae acquire similar or different energy metabolites for desiccation and starvation resistance. We tested the hypothesis whether larval acquisition of energy metabolites is consistent with divergence of desiccation and starvation resistance in darker and lighter isofemale lines of D. melanogaster. Our results are interesting in several respects. First, we found contrasting patterns of larval resource acquisition, i.e., accumulation of higher carbohydrates during 3rd instar larval stage of darker flies versus higher levels of triglycerides in 1st and 2nd larval instars of lighter flies. Second, 3rd instar larvae of darker flies showed ~40h longer duration of development at 21°C; and greater accumulation of carbohydrates (trehalose and glycogen) in fed larvae as compared with larvae non-fed after 150h of egg laying. Third, darker isofemale lines have shown significant increase in total water content (18%); hemolymph (86%) and dehydration tolerance (11%) as compared to lighter isofemale lines. Loss of hemolymph water under desiccation stress until death was significantly higher in darker as compared to lighter isofemale lines but tissue water loss was similar. Fourth, for larvae of darker flies, about 65% energy content is contributed by carbohydrates for conferring greater desiccation resistance while the larvae of lighter flies acquire 2/3 energy from lipids for sustaining starvation resistance; and such energy differences persist in the newly eclosed flies. Thus, larval stages of wild-caught darker and lighter flies have evolved independent physiological processes for the accumulation of energy metabolites to cope with desiccation or starvation stress.

Trade-off of energy metabolites as well as body color phenotypes for starvation and desiccation resistance in montane populations of Drosophila melanogaster

Storage of energy metabolites has been investigated in different sets of laboratory selected desiccation or starvation resistant lines but few studies have examined such changes in wild-caught populations of Drosophila melanogaster. In contrast to parallel selection of desiccation and starvation tolerance under laboratory selection experiments, opposite clines were observed in wild populations of D. melanogaster. If resistance to desiccation and starvation occurs in opposite directions under field conditions, we may expect a trade-off for energy metabolites but such correlated changes are largely unknown. We tested whether there is a trade-off for storage as well as actual utilization of carbohydrates (trehalose and glycogen), lipids and proteins in D. melanogaster populations collected from different altitudes (512–2500 m). For desiccation resistance, darker flies (> 50% body melanization) store more body water content and endure greater loss of water (higher dehydration tolerance) as compared to lighter flies (< 30% body melanization). Based on within population analysis, we found evidence for coadapted phenotypes i.e. darker flies store and actually utilize more carbohydrates to confer greater desiccation resistance. In contrast, higher starvation resistance in lighter flies is associated with storage and actual utilization of greater lipid amount. However, darker and lighter flies did not vary in the rate of utilization of carbohydrates under desiccation stress; and of lipids under starvation stress. Thus, we did not find support for the hypothesis that a lower rate of utilization of energy metabolites may contribute to greater stress resistance. Further, for increased desiccation resistance of darker flies, about two-third of total energy budget is provided by carbohydrates. By contrast, lighter flies derive about 66% of total energy content from lipids which sustain higher starvation tolerance. Our results support evolutionary trade-off for storage as well as utilization of energy metabolites for desiccation versus starvation resistance in D. melanogaster.

Activity Rhythm ofDrosophilaKept in Complete Darkness for 1300 Generations

Locomotor activity rhythms of dark stock flies of Drosophila melanogaster kept in complete darkness for 700 to 1340 generations were examined. The stock was established by the late Prof. S. Mori in November 1954 to investigate long-term effects of darkness on organisms. The activity of flies was recorded under three types of light conditions: DD after LD12:12, and DD after exposure to a 3.5 h (P3) or 7.5 h (P7) light pulse. In all of these conditions, the experimental dark flies exhibited clear circadian rhythms similar to those of control light flies. We compare our results with those of various studies on troglobites.

Phenotypic variability and sex dimorphism in Drosophila (Diptera: Drosophilidae): comparison of wild and laboratory grown adults of two sympatric cosmopolitan species

Phenotypic variability of several morphological traits was investigated in the two sibling cosmopolitan species (Drosophila melanogaster and D. simulans) collected simultaneously at the same place (Marrakech, Morocco). The phenotypic plasticity of wild living flies due to heterogeneous (but unknown) environmental conditions (HEC) was compared to the plasticity due to growth temperature in the protected environment of laboratory. Three metric, size-related traits were measured and 3 shape indices calculated. A meristic trait, thoracic bristles was also analyzed as well as another quantitative trait, abdomen pigmentation. Measurements were done on both sexes, allowing the analyses of sexual dimorphism. Developmental temperature in laboratory experiments (17 and 25 °C) confirmed a known plasticity, i.e. larger and darker flies at a lower temperature, while the bristle number was almost not affected. In nature, the main result was an average smaller size and a huge increase in the phenotypic variance of size. This suggests that, in nature, larval feeding conditions are less favorable and highly variable. Bristle number remained, as well as pigmentation, practically not affected by HEC. A negative correlation, between pigmentation and wing loading, suggested that, although wild flies were collected at the same time and place, the breeding sites were not exactly at the same temperature. D. simulans developed, on average, at a lower temperature than D. melanogaster, in agreement with a known behavioral difference, with respect to domestic habitats. Sexual dimorphism (SD) revealed a consistent shape difference between sexes, i.e. a more elongated thorax in females. In D. simulans size SD was significantly less in nature, suggesting that males were less affected by HEC. SD of pigmentation was always close to one in D. melanogaster, while it could be much more in D. simulans.

Correlated changes in thermotolerance traits and body color phenotypes in montane populations of Drosophila melanogaster : analysis of within‐ and between‐population variations

Thermotolerance traits vary across geographical gradients but there is a lack of clinal variation in some Drosophila species. Thus, it is not clear whether thermotolerance or other correlated traits are the target of natural selection. In order to test selection responses, we investigated body melanization and thermotolerance traits in six altitudinal populations of Drosophila melanogaster. Based on rearing different geographical populations under uniform growth conditions at 21 °C (common garden experiments), clinal variations for cold resistance are in the direction opposite to heat resistance along an altitudinal gradient, that is darker flies from highland populations evidenced higher levels of cold resistance while lowland populations showed higher heat resistance. Phenotypic plastic responses for body melanization at 17–28 °C showed significant correlations with thermotolerance traits. At 17 °C, regression coefficients as a function of altitude are highly significant and positive for cold resistance but negative for heat knockdown. However, for flies reared at 28 °C, there is no elevational change in melanization as well as thermotolerance traits. Thus, both genetic and plastic changes of body melanization and thermotolerance traits suggest a correlated selection response. Further, within-population analyses of body melanization (based on dark, intermediate and light color phenotypes) showed significant associations with thermotolerance traits. Correlated variations in body melanization and thermal tolerances are associated with climatic thermal variability (Tcv) but not with Tmin. or Tmax. along an altitudinal gradient.

Spineless Fish and Dark Flies Prove Gene Regulation Crucial

On page 1663 of this week's issue of Science and in last week's Science Express , two teams independently report that changes in regulatory DNA were responsible for an adaptation in natural populations of fish and insects. Each group has also pieced together details of the underlying genetic alterations in those animals.

Fitness consequences of body melanization inDrosophila immigransfrom montane habitats

AbstractWe investigated eight populations ofDrosophila immigransfrom low to high montane localities (600–2202 m) for altitudinal variations in abdominal melanization and fitness‐related traits (desiccation resistance, copulation duration, and fecundity). On the basis of common garden experiments, persistence between‐population differences at 21°C suggests that observed variations in fitness‐related traits have a genetic basis. Parent–offspring regression analyses showed higher heritability (h2= 0.77) for melanization patterns on all the abdominal tergites. All the traits showed significantly higher repeatability across generations. Under colder and drier environments in dispersed montane localities, abdominal melanization and desiccation resistance significantly increased (1.5–1.9 fold) along altitude. Thus, there are correlated effects of abdominal melanization on desiccation resistance. Genetic correlations, based on family means, were significantly high between abdominal melanization and other fitness traits. Furthermore, darker flies along increasing altitude resulted in a 35–40% increase in copulation duration as well as fecundity. There are significantly positive correlations of abdominal melanization with copulation duration as well as fecundity on the basis of within‐ as well as between‐population variations. Such observations are in agreement with the thermal budget hypothesis. Present data suggest that changes in body melanization impact fitness‐related traits in montane populations ofDrosophila immigrans.

Variations in body melanization impact desiccation resistance inDrosophila immigransfrom Western Himalayas

AbstractEctothermic species face problems of water balance under colder and drier climatic conditions in montane localities. We investigated five ecophysiological traits (body melanization, desiccation resistance, rate of water loss or gain and body size) in eight populations ofDrosophila immigransfrom an altitudinal gradient (600–2226 m) in the Western Himalayas. The traits showed bell‐shaped variability patterns characteristic of quantitative traits. For body melanization, we observed high heritability (0.65) on the basis of parent–offspring regression. A comparison of highland versus foothill populations showed significant divergence for all the traits except body size. Darker flies from the highlands exhibited higher desiccation resistance but reduced rate of water loss or gain as compared with lighter flies from the foothills, which showed lower desiccation resistance and higher rates of water loss as well as gain. Lack of differences in the amount of epicuticular lipids cannot account for differential reduction in cuticular water loss in altitudinal populations. However, within‐ as well as between‐population differences in body melanization can account for changes in desiccation resistance and reduction in cuticular water loss. Analyses of highland versus lowland populations as well as in assorted darker and lighter flies from a highland population have shown differences in haemolymph and dehydration tolerance. For the mechanistic basis of desiccation resistance, our results on wild populations ofDrosophila immigransare not in agreement with those reported for laboratory‐selected desiccation‐resistant strains inDrosophila melanogaster. Thus, ecophysiological mechanisms could be different under laboratory versus field selection.

Climatic adaptations of body melanisation in Drosophila melanogaster from Western Himalayas

We investigated population divergence in body melanisation in wild samples of Drosophila melanogaster across an elevational gradient (512 - 2202m) in the Western Himalayas. Wild populations are characterized by higher phenotypic variability as compared with laboratory populations. Significant differences in elevational slope values for three posterior abdominal segments (5th, 6th and 7th) in wild versus laboratory populations suggest plastic effects. However, elevational slope values do not differ for the three anterior abdominal segments (2nd, 3rd and 4th). Thus, elevational changes in melanisation include genetic as well as plastic effects. Fitness consequences of within population variability were analyzed on the basis of assorted darker and lighter flies from two highland as well as from two lowland localities. There is lack of correlation of melanisation with body size as well as ovariole number in assorted darker and lighter flies. For each population, darker flies showed higher desiccation resistance, lower rate of water loss, longer copulation duration and greater fecundity as compared with lighter flies. Phenotypic variations in body melanisation can be interpreted in relation with seasonal changes in temperature as well as humidity (Tcv and RHcv) of the sites of origin of populations. Thus, elevational changes in body melanisation may represent genetic response to selection pressures imposed by colder and drier climatic conditions in the Western Himalayas.

Changes in body melanisation and desiccation resistance in highland vs. lowland populations of D. melanogaster

Wild caught samples of Drosophila melanogaster from five highland localities showed parallel changes in melanisation and desiccation resistance in darker versus lighter phenotypes, i.e. darker flies (>45% melanisation) showed significantly higher desiccation resistance than lighter flies (<30% melanisation). In order to find an association between body melanisation and desiccation resistance, highland and lowland populations from tropical and subtropical regions (11.15–31.06°N) of the Indian subcontinent were raised and investigated at 21 °C for four physiological traits, i.e. per cent body melanisation, desiccation resistance, rate of water loss and rate of water absorption. On the basis of mother–offspring regression, body melanisation and desiccation resistance showed higher heritability (0.58–0.68) and thus these traits are suitable for laboratory analyses. Significantly higher melanisation as well as desiccation resistance were observed in highland populations as compared with lowland populations. The rates of water loss as well as absorption were negatively correlated with body melanisation, i.e. darker flies from highlands showed a reduced rate of water loss as well as a lower rate of water absorption while the reverse trend was observed in lighter flies from lowlands. On the basis of multiple regressions, significant effects due to combined altitude and latitude were observed for all the four physiological traits. Local climatic conditions (i.e. annual average temperature and relative humidity) helped in explaining parallel changes in body melanisation and desiccation resistance in D. melanogaster.

Temperature, urbanization and body color polymorphism in South Brazilian populations of Drosophila kikkawai (Diptera, Drosophilidae)

Body color polymorphism of urban populations of cosmopolite fly Drosophila kikkawai Burla, 1954 was investigated in relation to its possible association with environmental temperature. Samples of D. kikkawai were collected in spring, summer, autumn and winter between 1987 to 1988, in zones with different levels of urbanization in the southern Brazilian city of Porto Alegre, Rio Grande do Sul. A clear association was observed between darker flies and both seasons with low temperatures and areas of low urbanization (where temperature is generally lower than in urbanized areas). Results of preliminary laboratory experiments involving six generations of flies grown in chambers at temperatures of 17º and 25ºC confirmed this tendency to a relationship between body color and temperature, with allele frequency of the main gene involved in body pigmentation changing over time.

Survival of colour‐polymorphicEristalis arbustorumhoverflies in semi‐field conditions

1.The theory on adaptive phenotypic plasticity assumes different fitness optima in different environments. To demonstrate these fitness differences in the field or under laboratory conditions can be difficult.2.The size of the coloured patches on the abdomen ofEristalis arbustorumvaries with rearing temperature. At low temperatures small patches develop and at higher temperatures larger patches develop. Consequently, the colour patch size varies seasonally.3.To study the relative fitness of two extreme phenotypes in abdominal coloration in the summer, a total of 591 laboratory‐reared flies were released in six large population cages. As a measure of fitness, survival was estimated.4.In all replicate cages the survival of the pale phenotypes was higher than that of the dark phenotypes, indicating a higher fitness for the pale flies under summer conditions.5.The fat content of flies reared under identical conditions to those released in the cages was measured. Pale flies had ≈ 0·7 mg more fat than dark flies (± 25% extra fat). However, it is argued that this difference in fat reserves could not have been the only cause of the observed difference in survival.6.The results are discussed in relation to mimicry and thermoregulation.

Hygrothermal determinants of insect activity patterns: the Diptera of water‐lily leaves

Abstract. 1. The numbers and types of flies resting on water‐lily leaves varied through the diurnal cycle. The different patterns of occupancy were recorded in relation to time of day and to microclimatic conditions at the leaf surface.2. Overall fly activity on the leaves varied according to gross climatic patterns on particular days. The timing of activity differed according to species.3. Smaller, darker flies (especially ernpids and Notiphila) were common on the leaves early and late in the day, with the more reflective dolichopodids occurring only towards midday and in full sun. Hence there were clearcut correlations between both the size and reflectance properties of flies, and the climate (in particular radiation received at the leaf surface); though this pattern was superimposed on a diurnal activity effect.4. The timing of insect activity on the leaves could therefore be related to hygrothermal considerations, particularly the raising and maintenance of body temperature and avoidance of heat stress. Different types of fly used the favourable microclimate around the leaves as a resting site at times appropriate to their own biological requirements.

Influence of beta-alanine on mating and territorialism in Drosophila melanogaster.

Effects of beta-alanine on mating behavior and aggression were studied in Drosophila melanogaster using the following competitive pairs: (1) homozygous black (b/b) flies, in which beta-alanine synthesis is decreased, vs. alanine is blocked vs. wild-type (e+/e+) flies; (2) dark flies, in which beta-alanine incorporation is reduced, owing mainly to chromosome 3, vs. light flies collected from the same population as were the dark flies; (3) homozygous black (b/b) flies, in which beta-alanine synthesis is decreased, vs. beta-alanine-infected b/b flies, which are phenocopies of wild-type flies. The behavior of mixed-sex groups was studied in a large, illumination-graded observation chamber containing food and in small uniformly illuminated cells also containing food. The relative competitive mating abilities of these types were measured in both experimental conditions. Uninjected black flies, but not injected ones, showed weak and unsteady gait and weak wing extension. In ebony these abnormalities were more extreme. Dark flies did not show these abnormalities. Accelerated sexual maturation was indicated in males by early onset of courtship and enhanced territorial aggression and in females by earliness of mating. Such acceleration was observed in ebony and dark flies, compared with light flies, and among beta-alanine-injected b/b flies competing with uninjected black flies. Ebony males, although maturing earlier than wild-type males, were less successful than wild-type males in mating. This difference was even greater when the flies were all allowed to mature before competing. Ebony females outmated wild-type females. Dark flies outmated light flies, and beta-alanine-injected b/b males outmated uninjected black males, especially in bright light. Ebony flies mated much longer than wild-type flies, and black flies mated slightly longer than injected b/b flies. There was some spatial isolation of ebony from wild type, dark from light, and beta-alanine-injected from uninjected b/b flies in the illumination-graded observation chamber. Ebony flies more than wild type concentrated near food. Flies were attracted to the current of moist inlet air. They were also attracted to deposited excrement, and males defended such deposits as a mating area, thus showing rudiments of arena behavior in which a mating area away from the oviposition site is defended. Usually, however, the defended area focused on food.

ON THE ETHOLOGICAL DIFFERENTIATION OF DROSOPHILA ANANASSAE AND DROSOPHILA PALLIDOSA IN SAMOA.

A number of significant studies of genetic divergence and speciation in island populations of Drosophila have been undertaken in recent years. Certainly the grandest example of this has been the detailed study of the spectacular array of Drosophila species native to the Hawaiian Islands begun under the leadership of the late Professor Wilson S. Stone of the University of Texas and Professor D. Elmo Hardy of the University of Hawaii, and still being carried on by Hardy and a number of their colleagues; e.g., see Carson et al. (1970). Other island groups and Drosophila species have also been investigated by Stone and others at the University of Texas. Among these studies are those on Drosophila ananassae populations from island groups in the central and western Pacific Ocean, including light (brownish-yellow) and dark (blackish-brown) D. ananassae-like populations found on the American Samoan island of Tutuila. These populations are especially interesting in that, aside from the pigmentation difference, they are morphologically nearly indistinguishable and, in spite of exhibiting no apparent postmating reproductive barriers (Stone et al., 1966), they coexist together on this island as separate, reproductively isolated units. That they are sexually isolated has been shown cytologically (Futch, 1966) and ethologically (Futch, 1966; Spieth, 1966) with strains from Pago Pago, Tutuila. In recent years other collections of similar light and dark D. ananassae-like flies have been obtained from other islands in the Samoan archipelago as well as from islands in the Fijian group. Based mainly on the cytological and ethological evidence cited above concerning the genetic isolation of these light and dark forms, Bock and Wheeler (1972) recognize the two as distinct species belonging to the D. ananassae subgroup of the D. melanogaster species group of Drosophila. The dark flies have been identified as Drosophila ananassae Doleschall, a polytypic, widespread (circumtropical) domestic species of the tropical and sub-tropical world, whereas they describe the light flies as Drosophila pallidosa. This recently described species has a relatively localized distribution presently known only to include the southcentral Pacific islands of Samoa and Fiji where it exists side-by-side with its widely distributed sibling, D. ananassae. That two such very closely related, potentially interfertile sympatric species have been found living together successfully and separately in the island groups of Samoa and Fiji seems to warrant further investigation. As a part of this continuing investigation, populations from other islands of the Samoan group have been analyzed cytologically and for crossing fertility as stocks have become available to me.

Adaptative and selective responses of a population ofDrosophila melanogaster containinge ande+ to differences in temperature, humidity and to selection for developmental speed

Selection was carried out for 14 months in populations ofDrosophila melanogaster containing at the outset equal numbers ofe ande+ genes. High temperature and to a less extent low humidity as well as selection for propagation of early flies tended to favour the light wild type, whereas the opposite conditions favoured the dark (ebony) flies. However, only a low temperature brought about an actual increase ofebony. In none of the eight lines was one allele completely eliminated, the only difference being the different level of equilibrium and the speed with which it was approached. This indicates that in all the conditions tested in the laboratory the heterozygotes are superior to both homozygotes, the wild type being fitter than ebony at high temperatures and less fit at lower temperatures.Ebony flies were slower to develop under all conditions. More flies emerged from a bottle at high temperature than at low temperature, but they were lighter in weight. The latter difference, however, did not appear to be inherited.

A REVISED SYNOPSIS OF NEARCTIC THAUMATOMYIA (=CHLOROPISCA) (DIPTERA, CHLOROPIDAE)

Flies of the genus Thaumatomyia Zenker (=Chloropisca Loew) are small but common, and identification is frequenlly requested for faunal, ecological or other studies. Their highly polished, glabrous, usually yellow and black striped appearance stands out sharply among the many kinds of small dark flies captured by sweeping.