Inbreeding depression and male-mating behavior inDrosophila melanogaster

There have been relatively few studies designed to investigate the effects of inbreeding on behavioral traits. To study this phenomenon, five experimental lines ofDrosophila melanogaster made isogenic for chromosome 2 were evaluated for their male-mating ability and, subsequently, male courtship behavior. All lines showed significant reductions in overall mating ability, and males from all of these lines displayed impaired mating behavior, with two lines displaying particularly aberrant courtship patterns. Line 16 displayed an inability to successfully initiate copulation following successful courtship, while line 17 displayed significant reduction in locomotor activity, resulting in virtually no successful courtship or copulatory activity. The implications of these findings for competitive mating ability in wildDrosophila populations are presented. Further, the importance of mating success as a fitness component in the management of potentially highly inbred populations of endangered species is discussed.     

Decline in photopositive tendencies with age inDrosophila melanogaster (Diptera: Drosophilidae)

Phototaxis was measured in young, middle-aged, and oldDrosophila melanogaster flies of both sexes. The apparatus allowed us to measure the tendency to go toward light, independently of the time needed to do so; under such conditions, phototaxis is dissociated from locomotor activity. The percentage of photopositive flies decreased slightly with age (93.96, 80.17, and 78.97%, respectively, in young, middle-aged, and old flies). Results are discussed in connection with previous data for which the tendency to go toward light and the time to do so were not dissociated.     

The occurrence of the transposable elementpogo inDrosophila melanogaster

We examined the genomic occurrence of the transposable elementpogo in over 120 strains ofDrosophila melanogaster, from around the world and from different eras. All had multiple copies of a 2.1 kilobase (kb)pogo element, and multiple copies of several size classes between 1.0 and 1.8 kb. There were differences between strains in intensities or presences of deletion-derivative size classes, suggesting current or recent mobility in the species. We were unable to find anypogo-hybridization in eight other species in the genus, in three subgenera, or in the relatedScaptomyza pallida. Thepogo element may be a ‘middle-aged’ element in the genome ofD. melanogaster, having entered the species since its divergence from its sibling species, but long before theP andhobo elements.     

Rover/sitter foraging behavior inDrosophila melanogaster: Genetic localization to chromosome2L using compound autosomes

Genetic control of the rover/sitter behavioral polymorphism in Drosophila melanogasterlarvae was localized to the left arm of chromosome 2.Ten independent left and right compound second chromosomes were generated in isogenic rover and sitter strains by gamma irradiation and substituted into 25 different lines. Comparisons were made between lines to determine the chromosome arm contributions to rover/sitter phenotype expression.     

Suppression of abdominal legs inDrosophila melanogaster

Summary Drosophila melanogaster normally have six thoracic legs and no abdominal legs. However, one or two legs often appear in the first abdominal segment ofbithoraxoid mutants. The extent to which these extra legs develop is determined both by thecis-regulatory action ofbithoraxoid lesions onUltrabithorax and by the number of copies of the adjacent homeotic geneabdominal-A. Thebithoraxoid region does notcis-regulateabdominal-A.     

Transposable elements behavior following viral genomic stress inDrosophila melanogaster inbred line

To analyze the behavior of endogenous transposable elements under genomic stress, aDrosophila melanogaster inbred line was submitted to three kinds of viral perturbations. First, a retroviral plasmid containing the avian Rous Associated Virus type 2 (RAV-2) previously deleted for the viral envelope coding gene (env) was introduced by P element transformation into theDrosophila genome. An insertion of this avian retroviral sequence was detected byin situ hybridization in site 53C on polytene chromosome arm 2R. Second,Drosophila embryos were injected with RAV-2 particles produced by cell culture after transfection with the retroviral plasmid. Third, theDrosophila melanogaster inbred line was stably infected by the sigma native virus. It appears that neither the offspring of the flies in which the viral DNA was found integrated nor those from the infected sigma flies showed copia or mdgl element mobilization. Injection of the avian RAV-2 particles led, however, to the observation of somatic transpositions of mdgl element on the 2L chromosome, the copia element insertion pattern remaining stable. Thus, endogenous transposable elements show more instability in sublines injected with exogenous viral particles than in a transgenic subline containing a foreign viral insert, all transposable elements not being equally sensitive to such genomic stress. Correspondence to: I. Jouan-Dufournel     

Geographic differentiation in wing shape inDrosophila melanogaster

Genetic variation of a suite of 12 morphometric wing characters was examined in 16 natural populations ofDrosophila melanogaster from Eastern Europe and Central Asia using principal component analysis. The posterior wing compartment was found to differ in shape between the Eastern European and Central Asian populations. This result is in agreement with data on wing shape variation from exposure to high and low temperatures under laboratory conditions.     

World-wide variation inDrosophila melanogaster sex pheromone: behavioural effects, genetic bases and potential evolutionary consequences

InDrosophila melanogaster, male wing vibration, a key element of courtship behaviour, is most efficiently induced by a female-specific contact pheromonecis, cis 7,11 heptacosadiene (7, 11 HD), which is the main mature female cuticular hydrocarbon in the CS laboratory strain. A study of 63 strains from around the world revealed that flies from Sub-Saharan Africa and the Caribbean are unique in showing low levels 7,11 HD and high levels of the position isomer 5,9 HD. This difference maps to chromosome III, perhaps indicating a simple genetic control of the 7,11 HD: 5,9 HD ratio. Females from strains with high levels of 7,11 HD showed higher levels of mating and mated more rapidly than females with low levels of 7,11 HD. The results are discussed in light of recent discoveries of genetic differences betweenD. melanogaster strains from Africa and those from elsewhere around the world.     

Investigations on the PGM (phosphoglucomutase) polymorphism by isoelectric focusing inDrosophila melanogaster

Pgm allele frequencies of 383 individuals were determined in a sample ofDrosophila melanogaster from three laboratory Sardinian populations, using the techniques of standard electrophoresis, heat denaturation, and isoelectric focusing. The analysis of the progeny obtained from informative crosses showed that the isoelectric focusing patterns segregate in a Mendelian way. ThePgm ^1.00 andPgm ^0.70 electrophoretic alleles displayed different isoelectric points, whereas thePgm ^1.00,tr andPgm ^1.00,ts isoelectrophoretic alleles could not be differentiated when tested by isoelectric focusing. Moreover, thePgm ^0.70,ts allele was split into two classes, with isoelectric points ofpH 6.4 andpH 6.6.     

A correlation between juvenile hormone deficiency and vitellogenic oocyte degeneration inDrosophila melanogaster

Summary It is known from previous work that juvenile hormone (JH) is required to initiate vitellogenin uptake into maturing oocytes ofDrosophila melanogaster, but additional requirements for this hormone during oocyte maturation have not been fully understood. To determine if early vitellogenic oocytes (stages 8 and 9) require JH for continued development, these oocytes were transplanted toDrosophila female and male hosts which were rendered deficient in JH by three methods. Implanted stage 9 and usually stage 8 oocytes were found to degenerate in JH-deficient hosts unless ZR-515, a JH analogue, was applied to the host shortly after implantation.These results were confirmed during in situ ovary development. JH deficiency was produced in gravid females, and ovaries examined at subsequent time intervals were found to be deficient in stage 8–10 oocytes as early as 6 h after treatment. Degenerating oocytes corresponding to these stages were commonly found. ZR-515 prevented oocyte degeneration during at least the first 8 h and continued to support stage 8–10 oocyte development 24 h after application to these females. The results suggest that JH is required not only for initiation but also for continuation of vitellogenin uptake and oocyte development.     

Development time and pupation behavior in theDrosophila melanogaster subgroup (Diptera: Drosophilidae)

This study is an in-depth analysis of intersexual, intraspecific, and interspecific variability in larvopupal developmental time, pupation site preference, and larval and pupal survival of a number of isofemale lines of the speciesDrosophila mauritiana, D. melanogaster, D. sechellia, D. simulans, D. teissieri, andD. yakuba. There was no significant sex differences in pupation height, but females eclosed significantly earlier than males in all species. In addition, the suggestion of a strong negative correlation between larval developmental time and pupation height could not be confirmed in this study. The hypothesis that differences in pupation height provide a basis for niche partitioning between closely related species with overlapping distributions was tested by three planned orthogonal contrast analyses of variance. First, the two speciesD. teissieri andD. yakuba, with largely overlapping distribution, were significantly different in pupation height. Second, the two allopatric, nonoverlapping island speciesD. mauritiana andD. sechellia did not significantly differ in pupation height. However, the absence of a significant difference in the final contrast between the two cosmopolitan speciesD. melanogaster andD. simulans, which are often found together, makes us cautious to accept the hypothesis.     

Courtship inDrosophila sechellia: Its structure,functional aspects,and relationship to those of other members of theDrosophila melanogaster species subgroup

The courtship behavior of Drosophila sechelliais described. Male wing displays are mainly vibration and scissoring, with low levels of rowing. As courtship proceeds the proportion of courtship spent in male wing vibration and licking increases, whereas female movement decreases. The male courtship song of sechelliacontains pulse song but no sine song. This species also shows a distinctive copulation song associated with mounting and copulation. The main cuticular hydrocarbon in females is 7,11-heptacosadiene. The number of copulations increased when flies were placed in the presence of food. Visual and acoustic stimuli appear to be important for mating. A multidimensional comparison was used to compare members of the melanogaster species subgroup, based upon courtship behavior, song characteristics, and cuticular hydrocarbons. A multidimensional comparison of courtship sequences in sechellia, melanogaster, simulans,and mauritianashowed differences in variability between the two island species as compared to the two cosmopolitan species. The courtship song of D. orenais described: it shows both sine and pulse song; there is also a copulation song in this species.     

Localized synthesis of specific proteins during oogenesis and early embryogenesis inDrosophila melanogaster

Summary Protein synthesis in egg follicles and blastoderm embryos ofDrosophila melanogaster has been studied by means of two-dimensional gel electrophoresis. Up to 400 polypeptide spots have been resolved on autoradiographs. Stage 10 follicles (for stages see King, 1970) were labelled in vitro for 10 to 60 min with³⁵S-methionine and cut with tungsten needles into an anterior fragment containing the nurse cells and a posterior fragment containing the oocyte and follicle cells. The nurse cells were found to synthesize a complex pattern of proteins. At least two proteins were detected only in nurse cells but not in the oocyte even after a one hour labelling period. Nurse cells isolated from stages 9, 10 and 12 follicles were shown to synthesize stage specific patterns of proteins. Several proteins are synthesized in posterior fragments of stage 10 follicles but not in anterior fragments. These proteins are only found in follicle cells. No oocyte specific proteins have been detected. Striking differences between the protein patterns of anterior and posterior fragments persist until the nurse cells degenerate. In mature stage 14 follicles, labelled in vivo, no significant differences in the protein patterns of isolated anterior and posterior fragments could be detected; this may be due to technical limitations. At the blastoderm stage localized synthesis of specific proteins becomes detectable again. When blastoderm embryos, labelled in vivo, are cut with tungsten needles and the cells are isolated from anterior and posterior halves, differences become apparent. The pole cells located at the posterior pole are highly active in protein synthesis and contribute several specific proteins which are found exclusively in the posterior region of the embryo. In this study synthesis of specific proteins could only be demonstrated at those developmental stages which are characterized by the presence of different cell types within the egg chamber, while no differences were detected when stage 14 follicles were cut and anterior and posterior fragments analyzed separately. The differences in the pattern of protein synthesis by pole cells and blastoderm cells indicate that even the earliest stages of determination are reflected by marked changes at the biochemical level.     

Transmission of male recombination,segregation distortion and sex-ratio imbalance inDrosophila melanogaster

From the first test cross progenies of control (no larval transfers; no ethyl methanesulphonate), physical stress (two larval transfers; no ethyl methanesulphonate) and 0.75% ethyl methanesulphonate (two larval transfers; 0.75% ethyl methanesulphonate)-treated F₁ (Oregon K +/dumpy black cinnabar, dp b cn) males ofDrosophila melanogaster, respectively, 6,10 and 52 wild-looking first test cross males were again test crossed to obtain second generation. The overall percentages of male recombination detected in the second test cross progenies, in the three sets of experiments, were statistically the same as those in the first test cross progenies. Thus the enhanced male recombination caused by physical stress (with or without ethyl methanesulphonate) was transmitted to next generation. Non-reciprocal male recombination was observed indp b but not inb cn region in both first and second test cross progenies. Three abnormalities, (i) production of wild-type flies in majority overdp b cn type, (ii) Non-Mendelian segregation atdp b andcn loci and (iii) sex-ratio differences fordp bcn and +b cn types observed in test cross progenies of F₁ males ofDrosophila melanogaster were transmitted to next generation when induced with 0.75 % ethyl methanesulphonate but not when these abnormalities were induced with physical stress. The data suggest possible association of non-reciprocal male recombination, segregation distortion and sex-ratio imbalance inDrosophila melanogaster. In fact these may be representing different aspects of the same phenomenon     

Genetic mechanisms of early neurogenesis inDrosophila melanogaster

The neurogenic ectoderm ofDrosophila melanogaster consists of the ventral neuroectoderm and the procephalic neuroectoderm. It is hypothesized that epidermal and central neural progenitor cells separate from each other in three steps: conference on the neuroectodermal cells the capability of producing neural or epidermal progenies, separation of the two classes of progenitor cells, and specification of particular types of neuroblasts and epidermoblasts. Separation of neuroblasts and epidermoblasts in controlled by proneural and neurogenic genes.Delta andNotch serve as mediators of direct protein-protein interactions. E(spl)-C inhibits neurogenesis, creating epidermal cells. The achaete-scute complex (AS-C) controls the commitment of nonoverlapping populations of neuroblasts and leads the development of neuroectodermal cells as neuroblasts.     

Phenotypic expression of ADH regulatory genes inDrosophila melanogaster: a comparative study between a paleartic and a tropical population

In vitro ADH activity was studied inD. melanogaster males from two sets of third chromosome substitution lines, one from a paleartic population (Gigean, France), the other from a tropical population (Brazzaville, Congo). As a linear model with raw ADH activity dependent on fresh weight was significant in both sets of lines, the raw activity was adjusted by regression on weight. Two main results were found: (a) the well-known substantial intrapopulation variability; and (b) third chromosome geographical origin did not affect the mean ADH activity. Unlike the structuralAdh gene polymorphism which allows the two populations to be distinguished, the polymorphism of the third chromosome ADH regulatory genes (or more exactly their phenotypic expression) does not allow to discriminate between them. These results are discussed in the context of the adaptation ofD. melanogaster to the alcoholic substrates in light of a model proposed by Hedrick and McDonald (1980) in order to interpret variations in both structural and regulatory gene polymorphisms.