Neural Circuitry that Governs Courtship Behavior - Essay Example

Neural Circuitry that Governs Drosophila Male Courtship Behavior There have been studies conducted on the sexual behaviors among insects and perhaps the most considered subjects for experiments are the Drosophila species. Drosophila or fruit flies are two-winged insects and are usually modeled when it comes to genetic studies. They exhibit ideal complicated behaviors as well as optical recording and electrical neuronal activity. Indeed, analysis of male mating behavior unavoidably leads, therefore, to a consideration of the incomprehensible neural mechanisms that bring about the adaptive integration of various complicated sets of behaviors. This investigation is based on the premises of various authors and the essential points are presented herein chronologically: Ito ET. al. (1996) and Ryner et. al. (1996) shared that, sex differences in mating behavior and male sexual behavior among the Drosophila may be attributed to a single gene. Fru gene is created out of spliced transcripts from four distinct promoters. Lee et. al. (2000) added that, FruM is manifested in w2% of neurons in the Central Nervous System of male. These neurons are arranged into 21 distinct clusters in several regions of the ventral ganglia and brain, including some of the areas or regions implicated in male sexual behavior. Similarly, the complex behaviors of insects are related to the organization of their nervous system; the neural pathways from sensory to motor circuits must be properly explored to understand their behaviors; and focused also in the body electrophysiological nature (Lee, 2000). The male P1 transcripts according to Demir & Dickson (2005), encode male-specific proteins (FruM) which are both important and sufficient for male sexual behavior. The aforementioned literatures and those which were cited under the discussions and implications are quite reliable which supported the study. This research postulated that there are several fruGAL4-expressing neurons which are interconnected in a circuit and are involved in male sexual behavior. This circuit can be named accordingly: Sensory, central, and motor components. Basically, the study is directed towards exploration of the anatomy and physiology of target neurons that has influence over courtship behavior of the subjects. It also intended to assess whether "fruGAL4 reproduces the endogenous pattern of fru P1 transcripts". To achieve these, the proponents conducted gene targeting for labeling and manipulation of neurons, whereby they particularly add the GAL4 exposed reading frame to the fru P1 transcripts. In other words, various GAL4-responsive UAS transgenes were utilized. In fact, they also have stained brains and anterior nerve cords from fruGAL4, UAS-nlacZ heterozygous males with anti- "-galactosidase (anti-"-gal) and anti- FruM antibodies. The membrane tethered GFP reporter (UAS-mCD8-GFP) was utilized to closely observe the actual projection patterns of fruGAL4 neurons among the males and to find out for the potential differences in these projections among the females. Aside from this, to find out whether fru GAL4 ORNs work in male courtship behavior, an FLP-in strategy analogous to that one being used for their anatomical characterization was employed. Single-pair courtship assays were also prepared, in which males of these genotypes were joined to the wild-type virgin females. These assays were carried out in the dark in order to get rid of any visual cues that might affect or influence courtship, thereby increasing the male's reliance on chemosensory cues. Behavioral Assays, Immunohistochemistry and FLP-in-Silencing Constructs are all very powerful methods and fitted for the study. If we take a closer look on the assumptions and methods presented, the authors considered the classical as well as updated theories and principles for its variables. Thus, a very strong theoretical basis in the pursuit of the approaches or methods used has been established. Approaches utilized are congruent to the expected outcomes. The methods in genetics applied provided a uniquely powerful means to explore on the complex biological phenomenon of sexual behavior of the drosophila. It aided the determination of the mechanism of circuits and their functions. Understanding this, as well as molecular components underlying male sexual behavior can proceed to an appreciation of how the Central Nervous System directs a complex mechanical task. On the other hand, the next paragraph presents the conclusions drawn out from the experiments: First, fruGAL4 was found out to be specific, sensitive, and also a persistent marker for the FruM-expressing cells in the male Cental Nervous System. These are all highly desirable features. In specific, the persistence of the said marker is significant as it allows us to study the anatomy and function of all cells among the adult species, that express FruM, even if only not permanent during their progress or development in brains and that of ventral ganglia of 48 hr pupae as well as 2- to 3-day-old adults that are stained with anti-GFP and are examined by confocal microscopy. Moreover, no differences in the projection patterns of fruGAL4 neurons were detected between males and females. The projection patterns of fruGAL4 neurons may also be their connections and are totally similar in the male and female CNS. In addition, chemosensory pathways are noticeable, including both first order neuropils (the antennal lobe, the sub esophageal ganglion, for olfaction and also gustation, respectively). "The higher brain centers involved in chemosensory information processing (the mushroom bodies and superior medial and lateral protocerebrum), as well as the nerve bundles that interconnect these regions (such as the interantennal lobe tract and the median bundle). FruGAL4 fibers are absent in the visual pathways, that is from the first order neuropil (the lamina) however it is present in the second-, in the third-, and fourth-order neuropils (medulla, lobula and lobula plate, and optic tubercle, respectively) also, the nerve bundles that connect them. Same goes with the first order mechano-sensory neuropil, antennal-mechanosensory region, and in which labeled with fruGAL4" (Stockinger, Kvitsiani, Rotkopf, Tirin and Dickson, 2005). FruGAL4 motor neurons left the abdominal ganglia in the region of the abdominal nerve trunk and it innervates several ventral, also the dorsal abdominal muscles, as well as the male-specific muscle of Lawrence and the set of homologous but smaller muscles in females. Another branch of the abdominal nerve trunk carries fruGAL4 fibers that innervate the internal reproductive organs. In males, the reproductive organs specified includes the accessory glands, ejaculatory bulb, the aedeagus (penis) muscles, vas deferens, and a few bristles seminal vesicles, in the genital and anal plates. For the females, fruGAL4 neurons innervate the common and lateral oviducts, the uterus, and bristles in the genital plate. Furthermore, major gustatory, olfactory and auditory sites, fruGAL4 also labels a few sensory neurons at the maxillary palp, taste pegs on the inner of the labelum, in the cibarial organs of the mouth, the tarsi of the mid- and hind legs, the posterior radius of the wing, and of the genitalia. fruGAL4 is not manifested in the sensory neurons of the visual system. Another important finding here is that, "fruGAL4, eyFLP, UAS>stop>shits males courted significantly less than control males at the restrictive temperature, but not at the permissive temperature. Similar results were obtained upon constitutive silencing with TeTx. Attribute in the reduction in courtship to the silencing of the fruGAL4 ORNs cannot be definitely concluded, because in the corresponding fruGAL4, eyFLP, UAS>stop>mCD8-GFP flies, was detected. The mCD8-GFP reporter not just in the fruGAL4 ORNs, but also in the fruGAL4 neurons in Johnston's organ, many neurons in the optic lobe, and stochastically in a few neurons of the mushroom body or, rarely, in the ventral ganglia. In relation to sexual behavior, the reason why only males court and females do not may be attributed to some sexspecific property found in the fruGAL4 neurons. Only subtle variations or differences have been detected in the numbers of some neurons and in terms their projections and morphologies, there was no differences at all" (Stockinger, Kvitsiani, Rotkopf, Tirin and Dickson, 2005).Tentatively, it has been concluded that the sex differences has nothing to do in the production, connectivity or survival of the neurons involved. By examining the findings with the methods used, it can be observed that the techniques used are not monotonous but updated, which means that the author was able to maximize validity and reliability of results as much as possible. It is great to know that important techniques and proper measures were applied such as behavioral assays and immunohistochemistry techniques. Behavioral assays are techniques which could locate key genes that influence behaviors such as sexual behaviors among drosophila species. Genes can be mapped and further investigated. Immunohistochemistry refers to the steps involved in localizing proteins in cells or tissue section using the principle of antibodies binding particular only to certain antigens found in biological tissues. This is widely used to grasp understanding on the distribution and localization of biomarkers as well as differentially expressed proteins in some parts of a biological tissue. From these, the researcher can probably explore on expanded studies incorporating techniques such as trail-marking and foraging behavior through videography. This can be applied in both classical and contemporary experimental techniques. Aside from genetic markers in studies of communication among Drosophila. Group foraging dynamics and colony genetic structure investigations may also be explored. Another technique that can also be employed in closely the same investigation is the popular molecular phylogenetic analyses whereby sequence data from nuclear as well as mitochondrial genes to formulate phylogenetic relationships is noted among the insects with the aim of shedding light about social traits such as sexual behaviors. It is also further suggested, that utilization of hypotheses and other statistical treatments in the measure of characterization, differentiation as well as genetic variables of Drosophila to strengthen the tools and outcomes used. In every experimental study, there is no perfect method. Although various methods can work together and could come up with one good study. The work done may also be replicated so reliability of results may be better established. With regards to the results and discussions of this investigation, It seems that more discussions presented, were focused or based on other conducted studies by several scientists. It would probably make this study more meaningful if the discussions will practically highly and elaborate the findings based on the gathered data rather than giving emphasis to the results of researches which were conducted by other research scientists. Although related studies will enrich the results or findings upon thorough explanations and interconnecting the concepts, again, emphasis on the first hand data must be given more value. Perhaps lessons that can be learned here is that, there can be some practical engineering applications in the design to be integrated in the applied methods. Understanding of the gene expression patterns which can lead to expression of sexual behavior raises another broad interest and question such as how is behavior encoded in the DNA Are there "sex behavioral" genes, which are devoted to specific complex behavioral patterns Are these genes influenced by environment of experiences Perhaps, it would be a great challenge to establish a reliable method which could enable one to describe how exactly behaviors are encoded in the DNA. Let us be clarified however that in several related studies, experts highlight the essence and roles of stimulus and response, innate and learned behaviors, ethologic, impacts of real life experiences, territoriality, threats and other confounding variables that may affect also the sexual responses among Drosophila species. The researchers may replicate the same study with considerations to the above mentioned as the confounding variables. Finally, at this point, we may be lucky since there are fundamental aspects in the function and regulation of the nervous system which were established early in metazoan evolution that have been maintained despite the enormous change in scale that has occurred. The experimental power is now available in genetic models and can be combined with genome-based approaches in mammals. It may allow for more rapid progress in investigating and in understanding a complex behavior such as the male sexual behavior. Researchers may also continue to investigate how drosophila insects produce pheromones, explore factors how sexual response can be triggered, and what factors influences the response. This fascinating basic and applied research should be headed into more designs of new molecules which affect drosophila's response to pheromones. To better ways to use pheromones, including other compounds which may produce effects to their neurons. REFERENCE Stockinger, P., Kvitsiani, D., Rotkopf, S. Tirin, L. and Dickson, J. (2005) Neural crcuitry that governs drosophila male courtship behavior. Institute of Molecular Biotechnology of the Austrian Academy of Sciences Dr. Bohr-Gasse 3-5 A-1030 Vienna Austria. Cell, June, Vol.121, 795-807. Read More