The fruit fly, Drosophila melanogaster is an exceptional model species for understanding both proximate and ultimate causes of variation in behaviour. Here, we have examined two behaviors: foraging and mating. We discuss these research projects in turn. Almost 40 years ago, the classic foraging behaviour polymorphism rover/sitter was first discovered. Recently, evidence has suggested that the polymorphism is maintained by negative frequency-dependent selection at the larval stage. In two separate experiments we failed to replicate negative frequency-dependence in the survival of rover and sitter larvae. However, we empirically demonstrated differences in burrowing behaviour between the rover and sitter morphs which may be a possible mechanism causing the negative frequency-dependent relationship between the morphs. Future replication of negative frequency-dependence is necessary if we are to understand the maintenance of this polymorphism in nature. We examined mating behaviour from the perspective of two mechanisms of sexual selection: female choice and male-male competition. The study of sexual selection requires careful isolation of these mechanisms. Owing to difficulties in experimental design, studies have yet to properly separate and quantify the individual effects of female choice and male-male competition in fruit flies. Here, we designed a novel arena to assess true female choice. We then used this arena to test the effect of male courtship interference on mating outcomes. However, due to an unforeseen amount of male harassment of females in the arena, we withhold any strong conclusions about the effect of male-male interference behaviour. We also attempt to demonstrate the potential for sexual selection on traits associated with interference behaviour in males. / Thesis / Master of Science (MSc)

Complex behaviors using wings have facilitated the insect evolutionary success and diversification. The Drosophila indirect flight muscles (IFM) have evolved a highly ordered myofilament lattice structure and uses oscillatory contractions by pronounced stretch activation mechanism to drive the wings for high powered flight subject to natural selection. Moreover, the IFM is also utilized during small amplitude wing vibrations for species-specific male courtship song (sine and pulse), an important Drosophila mating behavior subject to sexual selection. Unlike flight, the contractile mechanism and contribution of any muscle gene in courtship song is not known. To gain insight into how separate selection regimes are manifested at the molecular level, we investigated the effect on flight and mating behaviors of mutations in two contractile proteins essential for IFM functions: an IFM-specific protein, flightin (FLN), known to be essential for structural and mechanical integrity of the IFM, and a ubiquitous muscle protein, myosin regulatory light chain (MLC2), known to enhance IFM stretch activation. Comparison of FLN sequences across Drosophila spp., reveal a dual nature with the N-terminal region (63 aa) evolving faster (dN/dS=0.4) than the rest of the protein (dN/dS=0.08). A deletion of the N-terminal region (fln�N62) resulted in reduced IFM fiber stiffness, oscillatory work and power output leading to a decreased flight ability (flight score: 2.8±0.1 vs 4.2±0.4 for fln+ rescued control) despite a normal wing beat frequency. Interestingly, the FLN N-terminal deletion reduced myofilament lattice spacing and order suggesting that this region is required to improve IFM lattice for enhancing power output and flight performance. Moreover, fln�N62 males sing the pulse song abnormally with a longer interpulse interval (IPI, 56±2.5 vs 37±0.7 ms for fln+) and a reduced pulse duty cycle (PDC, 2.6±0.2 vs 7.3±0.2 % for fln+) resulting in a 92% reduction in their courtship success. This suggested that FLN N-terminal region fine-tunes sexually selected song parameters in D. melanogaster, possibly explaining its hypervariability under positive selection. That FLN N-terminal region is not essential but required to optimize IFM functions of both flight and song, indicate that FLN could be an evolutionary innovation for IFM-driven behaviors, possibly through its role in lattice improvement. Mutations of the highly conserved MLC2 [N-terminal 46 aa deletion (Ext), disruption of myosin light chain kinase phosphorylations (Phos), and the two mutations put together (Dual)] are known to impair or abolish flight through severe reductions in acto-myosin contractile kinetics and magnitude of the stretch activation response. Unlike FLN, these MLC2 mutations do not show a pleitropic effect on flight and song. Flight abolished Phos and Dual mutants are capable of singing suggesting that these mutations affect song minimally compared to flight. Moreover, unlike FLN, none of these mutations affect interpulse interval, the most critical sexually selected song parameter in Drosophila. Also, in contrary to the known additive effects of Ext and Phos in the Dual mutant on flight wing beat frequency, a subtractive effect on sine song frequency is found in this study. That mutations in MLC2 are manifested differently for song and flight suggest that stretch activation plays a minimal or no role in song production. The results in this study suggest that the conserved regions of FLN and MLC2 are essential to support underlying IFM contractile structure and function necessary for flight, whereas the fast evolving FLN N-terminal region optimizes IFM's biological performance in flight and species-specific song possibly under positive selection regime.

Investigations of host-associated differentiation of parasitoids have largely focused on the degree of molecular genetic differentiation, but a true test of species status must examine the mating patterns of differentiated populations to determine if they can interbreed in the wild and produce viable offspring. We examined possible mechanisms of isolation between two genetically distinct host-plant complex races of the braconid, Cotesia congregata, originating from hosts on tobacco and catalpa. We compared male responses to female pheromones, elements of male acoustic courtship signals, and breeding success between the two races. Males responded to pheromones from both sources and male courtship signals showed only subtle differences, suggesting that factors other than courtship behavior may be involved in isolation of the two races. However, nearly 90% of females from one hybrid cross failed to produce offspring, leading to post-zygotic isolation. Development time, emerged brood size, and sex ratios between the races also differed.

No description available.

The decades following the Second World War witnessed a number of important developments affecting young people’s relationships and sexual lives, including the expansion of sex education initiatives and access to reliable contraception. The period has been heralded by some as one of ‘sexual revolution’, led by a rebellious youth whose views and practices were markedly different from those of their parents. This thesis examines the perspectives of young people growing up through these changes in Scotland, uncovering personal perceptions of their impact, or lack thereof, on their own emerging sexual lives. Whilst extant historical studies of sexuality in Scotland have focused on official perspectives and sexual governance, this thesis contributes to a history of sexuality ‘from below’, exploring the experiences of an untapped majority during a time of great change in heterosexual culture. Drawing on a series of oral history interviews with men and women growing up in various regions of Scotland between 1945 and 1980, evaluated alongside memoirs and contemporary surveys of sexual and contraceptive behaviour, this thesis examines the meanings and significance these developments held for young people in practice. These highly personal and subjective sources are key to understanding how young people learned about sexual matters, developed their ideas of appropriate conduct, and managed their early relationships and sexual behaviour. This research uncovers a piecemeal process of sexual learning against an atmosphere of mystery and shame, where educational initiatives and conversations on the topic were not necessarily comfortable or informative. Though growing numbers of young people were engaging in sexual activity outwith marriage, the illicit atmosphere they absorbed while growing up impacted on their perceptions of acceptable behaviour, and their ability to manage risk effectively and experience sex without anxiety. This was a time of flux for Scottish youth, who had to negotiate a path between traditional and liberal pressures, with resilient continuities evident in the form of rigidly gendered scripts defining appropriate behaviour, which continued to inform young people’s courtship practices and sexual experiences throughout the period. Interviewees detailed ongoing practical difficulties, for instance in obtaining contraception, alongside longstanding cultural concerns including the importance of reputation. Risk and fear of pregnancy remained preeminent throughout, despite the arrival of new options for young women in the form of the pill (latterly made available to the unmarried) and legal abortion. Gender, class, religion and region were all potentially significant in determining one’s experience of these issues. In all, the sources analysed here challenge conventional depictions of ‘sexual revolution’ and a confident, rebellious youth, with many interviewees feeling that the ‘Swinging Sixties’ was something that happened elsewhere. Changing patterns of behaviour were evident, but this was neither sudden nor revolutionary, and conventional attitudes to sex and relationships still held remarkable currency for many young people, with a clear separation of sex, marriage and childbearing only gaining ground from the later 1970s.

Two distinct nonapeptide systems, consisting of the vasotocin- and oxytocin-related peptides have evolved in vertebrates, and their role in male reproduction is well-described in mammals. In contrast, their comparative role in reproduction in basal vertebrate species, and teleost fishes in particular, has not been investigated in great detail. Using two cyprinid species, the zebrafish (D. rerio) and the goldfish (C. auratus), I address the hypothesis that the teleost nonapeptides vasotocin and isotocin stimulate male cyprinid reproductive physiology by affecting central neuronal and/or peripheral endocrine pathways. To test this hypothesis in zebrafish, an indeterminate breeder, I conducted pharmacological inhibition experiments employing vasotocin and isotocin-specific antagonists in males, a treatment predicted to inhibit reproductive success in mating trials. Because nonapeptides can act both as central peptide neuromodulators and as secreted hormone, I further quantified indices of male courtship behavior (nudging, circling and chasing) and major androgens (testosterone and 11-keto-testosterone) as key endocrine indices of the male reproductive axis. Together, these experiments revealed a dose-dependent, differential inhibition of spawning success, with significant reductions (-65%) in egg fertilization rate observed in pairs in which males had been i.p. injected with 5 ng/g vasotocin and significant reductions (-79%) observed at 500 ng/g i.p injected isotocin. In either case, these partial inhibitions of reproductive success were correlated with significant decreases in specific indices of male courtship behavior, but not endocrine indices, suggesting that individual nonapeptides mediate their effects via central modulation of behavioural neurocircuits. Interestingly, a co-administration of vasotocin and isotocin antagonists completely abolished reproductive success, however this effect was neither correlated with decreases in male courtship behavior, nor endocrine indices, suggesting a separate mode of action, possibly at the level of male pheromone release. To further probe the role of nonapeptides in male zebrafish reproduction, I subsequently tested the hypothesis that nonapeptide systems are acutely activated by key reproductive cues, specifically the releaser pheromone PGF2α, which serves as a chemoattractant and acutely stimulates male reproductive behavior in male cyprinids. Using a chemoattractant choice assay in conjunction with immunohistochemistry and gene expression approaches, I determined whether male zebrafish are attracted to pheromonal cues and acutely activate isotocinergic neurons in the short term and/or regulate nonapeptide gene expression in the longer term. My results show that individual male zebrafish are attracted to PGF2α in an acute choice test. Furthermore, an increase in p-ERK immunoreactivity, a marker of neuronal activation, was observed in the olfactory bulb 10 min following exposure, suggesting a specific response to the pheromone compared to EtOH vehicle. However, no co-localization of p-ERK and IT-positive perikarya was observed in the preoptic area (POA), refuting the hypothesis that PGF2α exposure acutely activates isotocinergic neurons in zebrafish. Analysis of whole brain relative mRNA transcript abundance revealed that PGF2α exposure time-dependently regulates whole brain isotocin, but not vasotocin transcript abundance, suggesting secondary longer-term effects of PGF2α exposure on the isotocinergic system. Using an analogous experimental approach, I further tested the hypothesis that nonapeptides stimulate male reproductive physiology in goldfish, a determinate breeder. Sexually mature male goldfish pretreated with saline or vasotocin or isotocin antagonists were exposed to saline or PGF2α-injected stimulus females and male courtship behavior (chasing, circling), endocrine indices (circulating testosterone) and milt release were quantified. Both nonapeptide antagonists reduced strippable male milt quantity in response to PGF2α-injected females, suggesting a neuronal or hormonal action of both nonapeptides on goldfish milt release. Together, I show that nonapeptides contribute to male reproductive physiology in two species of cyprinids with different reproductive tactics. However, the mode of action may differ from one species to another, with evidence suggesting that nonapeptides play a role in the regulation of reproductive behavior and, possibly, male pheromone, release in zebrafish, while effects on male goldfish seem to be exclusively related to the release of milt. Future studies should compare other teleost species with specific reproductive biology and focus on the gonadal roles of nonapeptides in sperm maturation and/or release.

No description available.

Thesis (Ph.D.)--McMaster University, 2005. / Advisor: Bennett Galef. Includes bibliographical references. Also available online.

Many species use color during courtship displays, with the more colorful individuals often selected as potential mates. Female blue crabs, Callinectes sapidus, display prominent red markings on their chelipeds, which is absent in males. I tested the hypothesis that females use this sexual dimorphism as an effective signal to potential mates. Body size was positively correlated with size of the colorful pattern on the crusher dactyl. Digital imaging techniques were used to examine and quantify a pattern of coloration in the female blue crab. Morphometric measurements were made using digital images of the carapace and chelae of crabs collected along the Gulf of Mexico coast in Galveston, Texas. Color complexity was examined on digital images of the chelae using Adobe? Photoshop? and Image J. Specific wavelengths were selected and their presence within the attribute quantified and evaluated. To determine whether male blue crabs prefer more colorful females, males were given a choice between females of different female coloration. Males displayed more often and directed more courtship displays towards the more colorful females. I hypothesize that male blue crabs use cheliped coloration as a visual cue for mate selection.

Thesis (Ph. D.)--University of Chicago, Dept. of Psychology, Human Development, August 2003. / Includes bibliographical references. Also available on the Internet.