The Effects of Genetic and Environmental Factors on the Reproductive Behaviors of Drosophila melanogaster
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The behavioral responses to varying environmental conditions and social interactions are multifaceted and require the coordination of complex neural circuits. Behaviors in animals are continuously affected by varying factors including, but not limited to, environment, genetic makeup, physiological state, or experience. Understanding the fundamental interactions between genotype, environment and phenotype is essential in understanding how evolutionary pressures shape behavior. In this dissertation, I used D. melanogaster to investigate various environmental and genetic components regulating the adult male and female mating behaviors. I explored the genetic components regulating different mating behaviors in adults by investigating the role of p24 proteins in male and female mating behaviors. p24 proteins comprise a family of type-I transmembrane proteins of ~24kDa that are present in yeast and plants as well as metazoans ranging from Drosophila to humans. These proteins are most commonly localized to the endoplasmic reticulum (ER)-Golgi interface and are incorporated in anterograde and retrograde transport vesicles. Drosophila melanogaster expresses nine p24 genes, grouped into four subfamilies. Based upon our mRNA and protein expression data, Drosophila p24 family members are expressed in a variety of tissues. To identify biological functions for particular Drosophila p24 proteins, we used RNA interference (RNAi) to reduce p24 expression. Ubiquitous reduction of most p24 genes resulted in complete or partial lethality during development. Reducing p24 levels in adults caused defects in female fecundity (egg laying) and reduced male fertility. We showed that reduced female fecundity is related to decreased neural p24 expression. These results provide the first genetic analysis of all p24 family members in a multi-cellular animal and indicate vital roles for Drosophila p24s in development and reproduction, implicating neural expression of p24s in the regulation of female behavior. Reproductive behaviors are also modified by social and environmental factors. Particularly, optimizing behavioral strategies that increase mating success are important, and prior sexual experiences as well as the current social environment can potentially affect an animal’s strategy for obtaining mates. Therefore, I investigated two separate scenarios, one where adult males were placed in a male-dense environment and their mating behaviors were quantified post male-male social interaction, and another scenario where the postmating behaviors of males were evaluated after achieving a successful sexual experience. Males reared in male-dense environments increased their mating durations with females, but do not affect the egg laying behavior or fecundity of the females. I found that although majority of the females remated with males within 24 hrs of the first mating, the prior social experience of the male did not influence the female remating latency. Males exposed to other males during early adulthood also did not have a competitive advantage against males raised in isolation. On the other hand, males with prior sexual experience changed their courtship dance and out competed sexually naïve males in the same mating arena. Females also preferred sexually experienced males by employing their auditory abilities to listen to the male’s modified courtship dance and responded positively by mating with them. Our findings have helped highlight the different behavioral responses shown by flies towards various environmental conditions.
Saleem, Sehresh (2014). The Effects of Genetic and Environmental Factors on the Reproductive Behaviors of Drosophila melanogaster. Doctoral dissertation, Texas A & M University. Available electronically from