7-tricosene and 7-pentacosene

Pheromones play a crucial role in mate stimulation and discrimination. In the fruit fly Drosophila, the most abundant cuticular hydrocarbons act as sex pheromones during courtship behavior. There are several active molecules and they compose a sex- and species-specific pheromonal bouquet. Different species from the Drosophila melanogaster subgroup have adopted alternative systems of chemical mate recognition. Recent exploration of these interspecific variations, and of intraspecific variations, has led to the characterization of genes and to the mapping of structures that process the production and perception of chemical messages.

Topics: Alkadienes; Alkenes; Animals; Brain; Drosophila; Drosophila melanogaster; Female; Hexanes; Hydrocarbons; Male; Pheromones; Sexual Behavior, Animal; Solvents; Species Specificity

In Drosophila, female hydrocarbons are known to be involved in premating isolation between different species and pheromonal races. The role of male-specific hydrocarbon polymorphism is not as well documented. The dominant cuticular hydrocarbon (CHC) in male D. melanogaster is usually 7-tricosene (7-T), with the exception of African populations, in which 7-pentacosene (7-P) is dominant. Here, we took advantage of a population from the Comoro Islands (Com), in which males fell on a continuum of low to high levels of 7-T, to perform temperature selection and selection on CHCs' profiles. We conducted several experiments on the selected Com males to study the plasticity of their CHCs in response to temperature shift, their role in resistance to desiccation and in sexual selection. We then compared the results obtained for selected lines to those from three common laboratory strains with different and homogenous hydrocarbon profiles: CS, Cot and Tai. Temperature selection modified the CHC profiles of the Com males in few generations of selection. We showed that the 7-P/7-T ratio depends on temperature with generally more 7-P at higher temperatures and observed a relationship between chain length and resistance to desiccation in both temperature- and phenotypically selected Com lines. There was partial sexual isolation between the flies with clear-cut phenotypes within the phenotypically selected lines and the laboratory strains. These results indicate that the dominant male pheromones are under environmental selection and may have played a role in reproductive isolation.

Topics: Alkenes; Animals; Chromatography, Gas; Comoros; Crosses, Genetic; Drosophila melanogaster; Female; Male; Pheromones; Reproductive Isolation; Selection, Genetic; Species Specificity; Temperature

D. simulans and D. melanogaster present two types of polymorphism in their cuticular hydrocarbon (HC) composition. Especially both sexes of D. simulans, and D. melanogaster males display 7-tricosene (7T) as the major compound type [7T]s and [7T]m, or 7-pentacosene (7P) [7P]s and [7P]m. D. melanogaster females display 7,11-heptacosadiene (7,11HD) as the major compound: [7,11HD]m, or 5,9-heptacosadiene (5,9HD): [5,9HD]m. The [7P]s, [7P]m and [5,9HD]m are mainly present in central Africa. A significant correlation was found between latitude and the proportion of compounds with 23 and 25 carbon atoms, especially 7T and 7P in both sexes of D. melanogaster. [7P]m type of D. melanogaster, characterized with an excess of C25 compounds, presents a higher resistance against desiccation than [7T]m type, where C23 compounds are more abundant. These differences can be correlated with calculated HC fusion temperatures. Moreover, increasing the breeding temperature from 18 to 29 degrees C induces in D. melanogaster males an increase in 25C compounds and a decrease in 23C compounds, but the opposite effect in D. simulans. A mathematical model of biosynthesis, based on kinetics of elongation and decarboxylation enzymes, suggests that a simple variation of the efficiency of an elongation enzyme may account for the differences observed between the [7T]m and [7P]m types of D. melanogaster and [7T]s and [7P]s types D. simulans. Finally on the basis of the geographical distribution of the HC types of both Drosophila species, an evolutionary dispersal pathway is proposed and discussed in relation to the environment and reproductive behavior.

Topics: Africa; Alkenes; Animals; Body Temperature; Breeding; Carbon; Dehydration; Drosophila; Drosophila melanogaster; Evolution, Molecular; Female; Genetic Variation; Geography; Hydrocarbons; Kinetics; Male; Models, Theoretical; Polymorphism, Genetic; Sex Factors; Species Specificity; Temperature

We have investigated the role of the Antennapedia and Bithorax complexes (ANT-C and BX-C) on the production of cuticular hydrocarbons in Drosophila melanogaster. In males, there is little, if any, influence of these complexes on the hydrocarbon pattern. In females, there are large and opposite effects of these complexes on diene production: two ANT-C mutations cause an increase in diene production and a reduction of monoenes, whereas most BX-C mutations result in a decrease in dienes and an increase in monoenes, although their sum remains constant. The effect is the highest in Mcp and iab6 females. It is suggested that a factor originating from the prothorax might activate the conversion of monoenes to dienes in females. The abdomen seems to have a crucial role in the production or control of pheromones: abdominal segments four to seven have the main effects, with a most dramatic effect for segments four and five.

Topics: Alkadienes; Alkenes; Animals; Antennapedia Homeodomain Protein; Drosophila melanogaster; Drosophila Proteins; Female; Gene Deletion; Gene Duplication; Genes, Homeobox; Genes, Insect; Heterozygote; Homeodomain Proteins; Male; Nuclear Proteins; Pheromones; Sex Determination Processes; Transcription Factors

7-tricosene (7T) and 7-pentacosene (7P) are the major components of cuticular hydrocarbons in Drosophila simulans and D. melanogaster males. A chemical study of 16 isofemale lines of D. melanogaster sampled at the first and eighth generations in laboratory conditions showed the stability of chromatographical profiles. Then a large scale study of male 7T/7P polymorphism was performed with 85 populations of D. melanogaster and 29 of D. simulans collected all over the world. There were significant correlations of the values of the balanced ratio (7T- 7P)/(7T + 7P) with geo-climatic parameters, such as latitude, longitude, mean temperature, temperature range and vapour pressure. Parallel variations were also reported for the homologous linear alkanes (23 and 25 Carbon atoms) but not for the longer branched alkanes (27 and 29 Carbon atoms). No correlation was significant for the D. simulans populations studied. In this species a similar polymorphism of 7T/7P was found but restricted to a few populations from West Equatorial Africa.

Topics: Adaptation, Physiological; Alkenes; Animals; Climate; Drosophila; Drosophila melanogaster; Female; Hydrocarbons; Male; Polymorphism, Genetic; Species Specificity

In Drosophila melanogaster, male courtship behaviour is genetically controlled and is influenced by sex pheromones. 7-tricosene (7-T) induces a dose-dependent inhibition of male-male courtship, whereas 7,11-dienes stimulate male courtship of females. There is a geographical quantitative variation in the production of two predominant male hydrocarbons, 7-T and 7-pentacosene (7-P). We have previously found that 7-P, the main hydrocarbon from males of West African strains, stimulates males that mainly produce 7-T. Using both 'natural' and genetically engineered strains, we find that genetic factors coding for low levels of 7-P in males have co-evolved with factor(s) coding for male responses to high levels of 7-P. These two phenotypes are coded by factors on different chromosomes: the intraspecific polymorphism for the production of 7-T and 7-P is largely controlled by chromosome 2, whereas the variation in courtship towards 7-P-rich males is largely controlled by chromosome 3. The polymorphism of male courtship towards 7-P-rich males shows no correlation with the variation in male responses to female flies.

Topics: Alkenes; Animals; Data Interpretation, Statistical; Drosophila melanogaster; Female; Genetic Variation; Male; Sex Attractants; Sexual Behavior, Animal; Species Specificity

7-tricosene (7-T) and 7-pentacosene (7-P) are the two main hydrocarbons on the cuticle of male Drosophila melanogaster. These two substances might play a pheromonal role during courtship behaviour. We investigated the genetic basis of the quantitative polymorphism observed in the production of 7-T and 7-P. Strains of different geographic origin, with males producing either predominantly 7-T or predominantly 7-P, were hybridized with strains carrying genetic markers. We found that chromosome II changes the balance between 7-T and 7-P while chromosome III regulates the overall quantity of both 7-monoenes. We have also characterized and roughly mapped sept and smoq, two genetic factors on chromosome II that act additively on the production of both cuticular hydrocarbons. The genetic control of the variation in 7-T and 7-P varies between D. melanogaster strains and between D. melanogaster and its sibling species D. simulans. The possible evolutionary and physiological causes of this variation as well as its functional implication for courtship behaviour are discussed.

Topics: Alkenes; Animals; Chromosome Mapping; Crosses, Genetic; Drosophila melanogaster; Gene Expression Regulation; Genes, Insect; Genotype; Male; Phenotype; Polymorphism, Genetic; Sex Attractants; Skin; Species Specificity

7-Tricosene and 7-pentacosene are predominant hydrocarbons on the cuticle of both sexes in Drosophila simulans. The pheromonal role of 7-tricosene has been clearly established for conspecific males, while a synergistic effect for 7-pentacosene has been postulated. Interstrain variation for the production of both compounds is very marked, but similar for both sexes. The genetic basis of this polymorphism was investigated. A major role was found for the second chromosome, which controls the 7-tricosene:7-pentacosene ratio. The main locus involved in controlling this variation, Ngbo, was mapped to position 65.3 on the second chromosome. The production of 7-pentacosene is directly related to the Ngbo genotype, which is additively expressed with two known alleles, Seychelles and Cameroon. These alleles act codominantly and are, respectively, hypomorphic and hypermorphic with regard to their effect on 7-pentacosene production. The production of 7-tricosene, which is partially inversely related to that of 7-pentacosene, is also affected by secondary interactions with the second chromosome and with the autosomal background.

Topics: Alkenes; Animals; Chromatography, Gas; Chromosome Mapping; Drosophila; Female; Genetic Variation; Hydrocarbons; Male; Pheromones; Polymorphism, Genetic