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PubMed2000

Inbreeding and outbreeding depression in male courtship song characters in Drosophila montana.

In Drosophila montana, male courtship song frequency is closely associated with male courtship success and offspring survival. Other pulse characters (pulse length and cycle number) may also affect female mate choice, whereas pulse train characters (interpulse interval, pulse number and pulse train length) are not associated with these male fitness components. Inbreeding depression in these song characters was investigated by comparing the songs of inbred and outbred fly strains. The average change in most song characters as a result of inbreeding was only a few percent. However, in male song frequency the average inbreeding depression was about 14%, suggesting that this song character is associated with fitness. Outbreeding depression and the genetic architecture of song characters were investigated with interpopulation crosses and joint scaling tests. For pulse train characters the generation means show only evidence of additivity, and the existence of dominance or epistasis in these characters was strongly rejected in each case. In pulse characters the means of the F1 males were lower than the average of the parental generations. In pulse length and cycle number this difference was attributable to dominance alone. In frequency there was outbreeding depression also in the F2 generation, suggesting a break-up of favourable epistatic gene combinations. The outbreeding depression in this character in the F1 generation was caused by dominance, and in the F2 also by duplicate epistasis between dominant decreasers. The possible role of outbreeding depression and epistasis in speciation is discussed.

Animal Communication↗
PubMed2000

Courtship and mating by the sandfly Phlebotomus duboscqi, a vector of zoonotic cutaneous leishmaniasis in the Afrotropical region.

Courtship behaviour of males of the Afrotropical sandfly Phlebotomus duboscqi Neveu-Lemaire (Diptera: Psychodidae) involved mounting the female and clasping her 'waist' with the male coxites placed between the female's thorax and abdomen. This behaviour, which we call 'piggy-backing', was preceded by male wing beating, perhaps involving mate recognition and contact pheromones. It did not seem to be pre- or postcopulatory mate guarding. Piggy-backing was attempted by P. duboscqi males on females of other species (P. papatasi and P. perniciosus) and even on other male P. duboscqi. The majority of female P. duboscqi piggy-backed by males were already inseminated, and most of the courting did not lead to copulation. This, coupled with the presence of a mating plug (semen) in each spermatheca of inseminated females, suggests that female P. duboscqi are monogamous for at least the first gonotrophic cycle. Male courtship with piggy-backing was more intense when females could feed on a hamster than when a hamster was present but the females were denied access to the host. It is suggested that, when a hamster was available to the females, the conditions in the laboratory are similar to those in rodent holes, the natural habitat of P. duboscqi.

Animals↗
PubMed2001

A central neural circuit for experience-independent olfactory and courtship behavior in Drosophila melanogaster.

We have studied the function of the major central olfactory pathway in fruit flies. Key elements of this pathway, the projection neurons (PNs), connect the antennal lobes with the lateral protocerebrum both directly and indirectly, the latter via the mushroom bodies (MBs). Transgenic expression of tetanus toxin in the majority of PNs and few MB neurons leads to defects in odor detection and male courtship. Considering behavioral data from flies lacking MBs, our results argue that the direct PN-to-lateral protocerebrum pathway is necessary and sufficient to process these experience-independent behaviors. Moreover, the involvement of an olfactory pathway in male courtship suggests a role of volatile attractive female pheromones in Drosophila.

Animals↗
PubMed1999

Widespread accumulation of [(3)H]testosterone in the spinal cord of a wild bird with an elaborate courtship display.

Elaborate courtship displays are relatively common features of the masculine reproductive behavior in birds. However, little is known about their neural and hormonal control. One bird that performs such a display is the golden-collared manakin (Manacus vitellinus) of Panamanian forests. Adult males, but not females, perform a physically intense display requiring substantial neuromuscular control of the wings and legs. We tested the hypothesis that steroid sensitivity is a property of neurons in the manakin spinal cord. Males and females were captured from active courtship leks, treated with drugs to block steroidogenesis, injected with (3)H-labeled testosterone, and the spinal cords were removed and processed for autoradiography. Sex steroid-accumulating cells were widely distributed in the spinal cords in each of six males and in one of five females. Cells, including presumptive motoneurons, reached their highest density in the ventral horns of the cervical and lumbosacral enlargements, regions associated with motor control of the wings and legs. These results suggest that neurons in the adult manakin spinal cord can express sex-steroid receptors, but do so less in females than in males. This evidence for androgen sensitivity and sexual dimorphism in the adult avian spinal cord suggests that sex steroids may control diverse behaviors in male birds in part by acting directly on the spinal neural circuits.

Animals↗
PubMed1999

Courtship Disruptions and Male Mating Strategies: Examples from Female-Defense Mating Systems.

Males frequently interrupt the copulation attempts of other males, and these courtship disruptions may limit the extent to which a few males are able to monopolize mating access to females. Males actively defend sexually receptive females in many species in which females form dense aggregations during the breeding season. Across and within such species there is considerable variation in the mating tactics adopted by males, with males in some cases defending groups of females and in other cases sequentially consorting with individual females. Colonial blackbirds have been central to studying this mating system, and we develop a conceptual model for how courtship disruption may account for variation in male mating tactics in this group. Our model assumes that the frequency of disruptions increases with greater colony size. As a consequence, successful copulations are less likely to occur at large colonies than at small colonies, and males are expected to switch from defending multiple females at the colony to consorting individual females away from it. Results from two species of blackbird support the basic assumptions of this model. In one species, the Montezuma oropendola, disruptions occur rarely and males defend groups of females, whereas in the other species, the yellow-rumped cacique, disruptions are frequent and males defend single females. Moreover, consistent with a key prediction, within each species, males associated with small colonies remain at the colony and defend groups of females, whereas males spend little time defending groups of females at large colonies and rarely attempt copulations there. This model has the potential to explain variation in male mating strategies and female monopolization for other taxa in which females form breeding aggregations.

Icteridae↗
PubMed1987

Behavioral and cytogenetic analysis of the cacophony courtship song mutant and interacting genetic variants in Drosophila melanogaster.

The courtship song of a Drosophila melanogaster male consists of tone pulses interspersed with humming sounds. An X chromosomal mutation, cacophony (cac), causes the production of polycyclic pulses readily distinguishable from those in wild type, which are mono- or bicyclic. Yet, courtship hums and flight wing beats are normal in this mutant, suggesting a specific role of the cac gene in the neural program underlying one particular feature of the fly's wing vibrations. A precise cytogenetic localization of cac is presented; this was obtained by uncovering the song abnormality with deletions that are missing all or the distal part of region 11A; the flies tested were diplo-X adults that had been turned into males by the transformer mutation. Duplications including distal 11A covered cac. The possibility of behavioral specificity for cac's effects was examined by screening a variety of sexual and nonsexual behaviors; these experiments included tests of flies in which the mutation was uncovered by a small deletion. We conclude that cac causes only a limited array of well-defined defects: longer and louder tone pulses in the song and depressed locomotor activity. Further complementation tests involving cac and other closely linked genetic variants--the night-blind-A (nbA) visual mutation, l(1)L13 lethal mutations, and a series of X chromosomal breakpoints--suggested complex interactions among these factors: the breakpoints uncover all three types of mutations; cac and nbA appear to be alleles of l(1)L13, whereas the two behavioral mutations complement each other.

Animals↗
PubMed1996

Bioassaying putative RNA-binding motifs in a protein encoded by a gene that influences courtship and visually mediated behavior in Drosophila: in vitro mutagenesis of nonA.

The no-on-transient-A (nonA) gene of Drosophila melanogaster influences vision, courtship song, and viability. The nonA-encoded polypeptide is inferred to bind single-stranded nucleic acids. Although sequence-analysis of NONA implies that it belongs to a special interspecific family of this protein type, it does contain two classical RNA recognition motifs (RRM). Their behavioral significance was assayed by generating transgenic strains that were singly or multiply mutated within the relatively N-terminal motif (RRM1) or within RRM2. Neither class of mutation affected NONA binding to polytene chromosomes. The former mutations led to extremely low viability, accompanied by diminished adult longevities that were much worse than for a nonA-null mutant, implying that faulty interpolypeptide interactions might accompany the effects of the amino-acid substitutions within RRM1. All in vitro-mutated types caused optomotor blindness and an absence of transient spikes in the electroretinogram. Courtship analysis discriminated between the effects of the mutations: the RRM2-mutated type generated song pulses and trains that tended to be mildly mutant. These phenotypic abnormalities reinforce the notion that nonA's ubiquitous expression has its most important consequences in the optic lobes, the thoracic ganglia, or both, depending in part on the nonA allele.

Animals↗
PubMed1998

Courtship and visual defects of cacophony mutants reveal functional complexity of a calcium-channel alpha1 subunit in Drosophila.

We show by molecular analysis of behavioral and physiological mutants that the Drosophila Dmca1A calcium-channel alpha1 subunit is encoded by the cacophony (cac) gene and that nightblind-A and lethal(1)L13 mutations are allelic to cac with respect to an expanded array of behavioral and physiological phenotypes associated with this gene. The cacS mutant, which exhibits defects in the patterning of courtship lovesong and a newly revealed but subtle abnormality in visual physiology, is mutated such that a highly conserved phenylalanine (in one of the quasi-homologous intrapolypeptide regions called IIIS6) is replaced by isoleucine. The cacH18 mutant exhibits defects in visual physiology (including complete unresponsiveness to light in certain genetic combinations) and visually mediated behaviors; this mutant (originally nbAH18) has a stop codon in an alternative exon (within the cac ORF), which is differentially expressed in the eye. Analysis of the various courtship and visual phenotypes associated with this array of cac mutants demonstrates that Dmca1A calcium channels mediate multiple, separable biological functions; these correlate in part with transcript diversity generated via alternative splicing.

Alleles↗
PubMed2005

Lineage-specific differences in evolutionary mode in a salamander courtship pheromone.

Functionally equivalent genes may evolve heterogeneously across closely related taxa as a consequence of lineage-specific selective pressures. Such disparate evolutionary modes are especially prevalent in genes that encode postcopulatory reproductive proteins, presumably as a result of sexual selection. We might therefore expect genes that mediate reproduction prior to insemination to evolve in a similar manner. Plethodontid receptivity factor (PRF), a proteinaceous salamander pheromone produced by the male, increases female receptivity during courtship interactions. To test for lineage-specific differences in PRF's evolution, we intensively sampled PRF genes across the eastern Plethodon phylogeny (27 spp.; 34 populations) to compare gene diversification, rates of evolution, modes of selection, and types of amino acid substitution. Our analyses indicate that PRF evolutionary dynamics vary considerably from lineage to lineage. Underlying this heterogeneity, however, are two well-defined transitions in evolutionary mode. The first mode is representative of a typical protein profile, wherein neutral divergence and purifying selection are the dominant features. The second mode is characterized by incessant, cyclical evolution driven by positive selection. In this mode, the positively selected sites are bound by a limited assortment of acceptable amino acids that appear to evolve independently of other sites, resulting in a tremendous number of unique PRF alleles. Several of these selected sites are implicated in receptor binding. These sites are apparently involved in a molecular tango in which the male signal and female receptors coevolve within a confined molecular space. PRF's lineage-specific evolutionary dynamics, in combination with evidence of a molecular tango, highlight the molecular action of sexual selection on a chemical signal that is used during courtship.

Amino Acid Sequence↗
PubMed2006

A female-specific desaturase gene responsible for diene hydrocarbon biosynthesis and courtship behaviour in Drosophila melanogaster.

Drosophila melanogaster shows sexually dimorphic cuticular hydrocarbons, with monoenes produced in males and dienes produced in females. Here we describe a female-specific desaturase gene, desatF. RNAi knock-down led to a dramatic decrease in female dienes and increase in monoenes paralleled with an increase in copulation latency and a decrease in courtship index and copulation attempts by the males. The desatF gene was also expressed in females from D. sechellia, rich in dienes, but not D. simulans, which produce only monoenes. When hydrocarbons were feminized in D. melanogaster males by targeted expression of the transformer gene, the expression of desatF occurred. These results strongly suggest that desatF is a crucial enzyme for female pheromone biosynthesis and courtship behaviour in D. melanogaster.

Amino Acid Sequence↗
PubMed2005

Analysis of a complex vertical copulatory-courtship display in the yellow fever vector Sabethes chloropterus.

Sabethes chloropterus (Von Humboldt) (Diptera: Culicidae), an arboreal mosquito vector of the yellow fever virus, perches on vertical surfaces, where airborne males patrol for potential mates and mating occurs. Laboratory analysis of 26 virgin mating pairs partly confirms and greatly extends an earlier description suggesting that males perform a courtship ritual. A male approaches a female by hovering behind her, moving toward her from one side, reaching toward her and occasionally touching her with his closest midleg, and eventually seizing her wing with that midleg and inverting beneath her, forelegs against the substrate. Immediately after male alignment with the female, the pair enters a superficial genital-coupling phase, in which the male's extended gonostyli are linked to the female, and he proceeds sequentially through four stages of midleg oscillations (MLOs): Alternate I, Synchronous I, Double-flex, and Synchronous II. Following one or more genital thrusts, the pair shifts to a full-copulation phase, which lasts only up to 6 s, during which the genitalia are clasped and insemination occurs. The male raises his midlegs and hindlegs in succession, then performs Alternate II MLO until the female kicks him and he is released. Nineteen (73%) of the 26 pairs successfully completed the entire sequence, including genital shift and full copulation, taking an average of 3.7 min. Features of the display that might determine success were not evident. Reversions in the chain of events occurred, but linear progression of stages and phases was characteristic of nearly all matings. The male's approach, however, lacked stereotypic form and probably is not part of the courtship.

Animals↗
PubMed1993

Rapid neurophysiological effects of corticosterone on medullary neurons: relationship to stress-induced suppression of courtship clasping in an amphibian.

Courtship clasping of females by male roughskin newts (Taricha granulosa) is rapidly blocked by exposure to corticosterone (CORT). This behavioral effect appears to result from CORT binding to a receptor in neuronal membranes. The present study investigated effects of intraperitoneal CORT administration on neurophysiological properties of extracellularly recorded single medullary neurons in acutely prepared newts. CORT produced multiple neurophysiological effects that emerged within 3 min of injection and increased in magnitude during the next 20-30 min. Spontaneously active and sensory-responsive neurons showed a decline or cessation of firing concomitant with a loss of sensory responsiveness, especially to cloacal pressure, a clasp-facilitating stimulus in behaving newts. After CORT administration, reticulospinal neurons that were backfired (antidromically activated) by spinal cord stimulation, exhibited reduced antidromic action potential amplitude, slowed rates of spike generation and other indications of reduced excitability. Comparable effects of CORT were also evident in newts with a premedullary brainstem transection, indicating a direct hormone action on the caudal neuraxis. Dexamethasone (DEX), a glucocorticoid that binds poorly to the CORT membrane receptor and has little effect on clasping, had little or no direct neurophysiological effect, but DEX injection 30 min before CORT interfered with the neurophysiological action of CORT. The rapidity, time course and specificity to CORT of these neurophysiological effects are consistent with mediation through the CORT membrane receptor. In addition, the pattern and dose sensitivity of these neurophysiological actions plus their occurrence in the medulla, suggest that they could underlie the CORT effect on courtship clasping.

Action Potentials↗
PubMed1986

Courtship and copulation in Tarsius bancanus.

The reproductive behavior of 6 paired, captive Bornean tarsiers was studied over an 8-month period. Seven copulations were observed. Females signalled males by visual displays and olfactory cues from vulval rubbing. Males signalled females with courtship calls heard before matings. After a courtship lasting from 1 to 2 h, copulation occurred with the male thrusting 61-190 times for 60-90 s, ending in ejaculation. The female regulated timing of mating by rejection or avoidance of the male. Multiple matings were not observed, and mating occurred once or twice a night during each night of estrus. This copulatory pattern of infrequent matings of short duration and active female solicitation and regulation of copulating timing suggests a harem or monogamous system.

Animals↗
PubMed1984

Courtship stimulates aromatase activity in preoptic area of brain in male ring doves.

Aromatase activity was quantified in vitro in different regions of the basal forebrain of male ring doves at various times after the initiation of courtship. By 24 h after the introduction of a female dove into the cage of a male, there was a significant, nearly two-fold, increase in aromatase activity which was confined to the ventromedial preoptic area (VM-POA) where enzyme activity was concentrated. This increase in aromatase activity, which was sustained through day 5 of courtship, presumably serves to activate nest-oriented behavior.

Animals↗
PubMed2002

The Drosophila Pox neuro gene: control of male courtship behavior and fertility as revealed by a complete dissection of all enhancers.

We have dissected the entire cis-regulatory region of the Drosophila Pox neuro gene with regard to its enhancers, and have analyzed their functions by the selective addition to Pox neuro null mutant flies of one or several functions, each regulated by a complete or partial enhancer. We have identified at least 15 enhancers with an astounding complexity in arrangement and substructure that regulate Pox neuro functions required for the development of the peripheral and central nervous system and of most appendages. Many of these functions are essential for normal male courtship behavior and fertility. Two enhancers regulate the development of the penis, claspers and posterior lobes of male genitalia. Three enhancers, two of which overlap, control the development of chemosensory bristles in the labellum, legs and wings, some or all of which are required for the transmission of gustatory signals elicited by female pheromones. An additional enhancer regulates in the developing brain the connectivity of two specific neuronal clusters entrusted with processing olfactory pheromone signals from the antennal nerve. Finally, functions crucial for the ability of the male to copulate depend on an enhancer that activates Pox neuro expression in the embryonic ventral cord. In addition to these male courtship and fertility functions of Pox neuro, we have identified enhancers that regulate: (1) proper segmentation of tarsal segments in the leg disc and in homologous segments of the antennal disc; and (2) proper development of the wing hinge and hence the ability of the fly to fly.

Alleles↗
PubMed2000

Molecular and behavioral analysis of sex-linked courtship song variation in a natural population of Drosophila melanogaster.

Genes controlling the "lovesong" in Drosophila are particularly interesting under a evolutionary point of view as they could be involved in the reproductive isolation between closely related species and, as a consequence, in the speciation process. We carried out a survey of sex-linked molecular and behavioral courtship song variation in 27 lines derived from a natural population of Drosophila melanogaster in Italy. We sequenced a 983 bp fragment of cacophony(cac), a calcium channel gene controlling aspects of the courtship song. The same region was also sequenced in a D. simulans strain. Only 5 non-coding sites were polymorphic among the D. melanogaster lines, and no amino acid substitutions were found between the two species. Statistical tests applied to the data did not reveal any significant deviations from a neutral model. Using the same lines we also carried out an analysis of three different song parameters which are known to be affected by the cac(S) song mutation: interpulse-interval (IPI), pulse amplitude (PA) and cycles per pulse (CPP). We found significant differences among the lines in IPI and PA, and for the latter a significant association with one of the polymorphic sites of cac.

Analysis of Variance↗
PubMed1991

The effect of the homoeotic mutation, Spineless-aristapedia, on female receptivity to male courtship in Drosophila melanogaster.

Drosophila melanogaster females expressing the homoeotic mutation, spineless-aristapedia (SSa), were tested for their ability to hear the song of courting males. Since courtship song increases a females' receptivity to copulation, the frequency of mating within a short observation period was used as a measure of the ability of mutant females to distinguish between singing males and males that were unable to sing. These results show that SSa females, although lacking aristae, could distinguish between the two types of males in that they mated more readily with males that sang. Furthermore, the homoeotic legs of SSa females are not required to be present for the detection of courtship song, since females whose homoeotic legs were removed could still distinguish between singing and non-singing males.

Animals↗
PubMed1996

Temporally manipulated rescue of visual and courtship abnormalities caused by a nonA mutation in Drosophila.

The no-on-transient-A gene was identified by independently isolated mutations causing visual-response abnormalities or courtship song defects. The nonA(diss) mutant is abnormal for all of these phenotypes. The pleiotropic effects of this dissonance allele dovetail with the widespread tissue expression of the nonA products. This gene, which encodes a putative RNA-binding protein, is expressed at essentially all stages of the life cycle. To determine whether the behavioral and physiological abnormalities exhibited by nonA mutant adults have a developmental etiology or are the result of an impaired mature nervous (or perhaps neuro-muscular) system, a conditional form of this gene was constructed. Animals from the resulting hsp-nonA (cDNA) transgenic strain were subjected to heat-shock regimes such that the gene's coding sequences were activated during development only, solely in the imaginal stage, or both. Surprisingly, expression during any of these time periods effected rescue of the visual-response and the courtship-song defects.

Animals↗