Spiral groove seal

Mating flat surfaces inhibit leakage of a fluid around a stationary shaft. A spiral groove produces a pumping action toward the fluid when the shaft rotates. This prevents leakage while a generated hydraulic lifting force separates the mating surfaces to minimize wear. Provision is made for placing these spiral grooves in communication with the fluid to accelerate the generation of the hydraulic lifting force

The limits of mean-field heterozygosity estimates under spatial extension in simulated plant populations

Computational models of evolutionary processes are increasingly required to incorporate multiple and diverse sources of data. A popular feature to include in population genetics models is spatial extension, which reflects more accurately natural populations than does a mean field approach. However, such models necessarily violate the mean field assumptions of classical population genetics, as do natural populations in the real world. Recently, it has been questioned whether classical approaches are truly applicable to the real world. Individual based models (IBM) are a powerful and versatile approach to achieve integration in models. In this study an IBM was used to examine how populations of plants deviate from classical expectations under spatial extension. Populations of plants that used three different mating strategies were placed in a range of arena sizes giving crowded to sparse occupation densities. Using a measure of population density, the pollen communication distance (Pcd), the deviation exhibited by outbreeding populations differed from classical mean field expectations by less than 5% when Pcd was less than 1, and over this threshold value the deviation significantly increased. Populations with an intermediate mating strategy did not have such a threshold and deviated directly with increasing isolation between individuals. Populations with a selfing strategy were influenced more by the mating strategy than by increased isolation. In all cases pollen dispersal was more influential than seed dispersal. The IBM model showed that mean field calculations can be reasonably applied to natural outbreeding plant populations that occur at a density in which individuals are less than the average pollen dispersal distance from their neighbors

The role of the male produced pheromone in the reproduction behaviour of the southern armyworm Pseudaletia separata (Wlk.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology.

Detailed courtship patterns have been described for few species of Lepidoptera. Most of the descriptive work in the literature is fragmentary or lacking in experimental or statistical analysis. Brower, Brower, and Cranston (1965) working on wild populations of the queen butterfly Danaus gilippus berenice have statistically analysed the probability of each movement in the sequence and have given a reliable and detailed account of mating in this species. Tinbergen (1958) by the presentation of models of varying size and colouration, and examining the affect of removal of structures suspected to be important in courtship has produced a good experimental account of mating in Satyrus semele the grayling butterfly. Because of the greater difficulties of observing complete mating sequences of nocturnal insects in the wild, most moth studies have been carried out with small caged populations. Again detailed expermental work is rare. The studies of Shorey (1964) on the cabbage looper Trichoplusia ni and Birch (1970) on the angleshades moth Phlogophora meticulosa possess good experimental detail suggesting that chemical cues are much more important in the courtship of moths than in butterflies. Development of more definitive techniques has allowed the investigation of insect courtship to move from subjective descriptions of the movement sequence to precise studies of the visual, tactile and chemical cues. In particular the availability of gas chromatography and mass spectrometry techniques capable of detecting the very small amounts of material produced by insects, has revolutionised the study of the chemicals, or pheromones, that are used in intra- specific communication.[FROM INTRODUCTION

The Evolution of Language Groups among Cooperating Digital Predators

Many species of animals have evolved complex means for communicating with one another. Oftentimes, communication is essential for the execution of tasks that require cooperation between individuals, such as group hunting and mate selection. As a result, communication itself becomes essential for survival. While these facts are readily observed, the evolutionary processes underlying them are less understood, in large part because observational - much less controlled - studies of these processes are impossible. Both the timescales and population sizes required for such studies are simply too great. To address these problems, this thesis uses simulated predators to study the evolution of language in animals. These digital predators evolve to perform two cooperative tasks: hunting and mate selection. After the populations of predators have evolved to perform both tasks successfully, the population is decomposed into both language groups and cooperative groups. Spectral clustering identifies predators that speak similar languages, while merge clustering is used to find those groups of predators that are the most successful when working together. Analysis of the groups generated by these two different methods shows that the most successful pairings are not necessarily those in which the two individuals are speaking the same language. Rather, organisms can evolve to speak a different language than the one to which they respond. Moreover, even though one task -- mate selection -- evolves earlier in evolutionary history, the language diversity it produces counteracts any head-start provided for the evolution of the second task. Thus, not only is language important for the evolution of cooperative task success, but the appearance of language groups can also play a determinant role in the evolution of cooperation.Computer Science

Calls and Couples: Communication, Connections, Joint-Consumption and Transfer Prices

The article explores joint consumption equilibrium environments. It illustrates network formation through one-to-one directional synapses. Family (couple) arrangements, spontaneously generated under a decentralized general equilibrium price system are suggested - involving link and direction-specific transfer prices along with standard resource one. The research also inspects preference characteristics able to generate monogamous choices and assortative matching and mating. Assortative mating (and income pooling) is clarified, related to exclusivity or taste-for unicity at the utility level with respect to shared good, with optimal assignment connected to equalization of the marginal benefit of the match - adequately defined - across individuals in the economy. Contrast with a multiple external effect good - one-to-many communication; (or) shared by a fixed number of, more than two, individuals; common property - and with a pure public good is also provided. If paired consumption with end-point specificity generates (or may generate), under reasonable assumptions, a unique decentralized equilibrium solution, supporting an efficient allocation, multiple agent sharing among more than two individuals and individual types requires, along with excludability, perfect differentiation of a larger number of consumption - partnership - roles.Shared goods, Joint consumption, Cost-sharing, Communications, Call, Linkage, Network nodes, Synapses, Matching, (Assortative) Mating, Couple goods, Family formation, Dowry, Transfer prices, Theory of the firm

Microguards and micromessengers of the genome

The regulation of gene expression is of fundamental importance to maintain organismal function and integrity and requires a multifaceted and highly ordered sequence of events. The cyclic nature of gene expression is known as ‘transcription dynamics’. Disruption or perturbation of these dynamics can result in significant fitness costs arising from genome instability, accelerated ageing and disease. We review recent research that supports the idea that an important new role for small RNAs, particularly microRNAs (miRNAs), is in protecting the genome against short-term transcriptional fluctuations, in a process we term ‘microguarding’. An additional emerging role for miRNAs is as ‘micromessengers’—through alteration of gene expression in target cells to which they are trafficked within microvesicles. We describe the scant but emerging evidence that miRNAs can be moved between different cells, individuals and even species, to exert biologically significant responses. With these two new roles, miRNAs have the potential to protect against deleterious gene expression variation from perturbation and to themselves perturb the expression of genes in target cells. These interactions between cells will frequently be subject to conflicts of interest when they occur between unrelated cells that lack a coincidence of fitness interests. Hence, there is the potential for miRNAs to represent both a means to resolve conflicts of interest, as well as instigate them. We conclude by exploring this conflict hypothesis, by describing some of the initial evidence consistent with it and proposing new ideas for future research into this exciting topic

Gestural Communication and Mating Tactics in Wild Chimpanzees

The extent to which primates can flexibly adjust the production of gestural communication according to the presence and visual attention of the audience provides key insights into the social cognition underpinning gestural communication, such as an understanding of third party relationships. Gestures given in a mating context provide an ideal area for examining this flexibility, as frequently the interests of a male signaller, a female recipient and a rival male bystander conflict. Dominant chimpanzee males seek to monopolize matings, but subordinate males may use gestural communication flexibly to achieve matings despite their low rank. Here we show that the production of mating gestures in wild male East African chimpanzees (Pan troglodytes schweunfurthii) was influenced by a conflict of interest with females, which in turn was influenced by the presence and visual attention of rival males. When the conflict of interest was low (the rival male was present and looking away), chimpanzees used visual/ tactile gestures over auditory gestures. However, when the conflict of interest was high (the rival male was absent, or was present and looking at the signaller) chimpanzees used auditory gestures over visual/ tactile gestures. Further, the production of mating gestures was more common when the number of oestrous and non-oestrus females in the party increased, when the female was visually perceptive and when there was no wind. Females played an active role in mating behaviour, approaching for copulations more often when the number of oestrus females in the party increased and when the rival male was absent, or was present and looking away. Examining how social and ecological factors affect mating tactics in primates may thus contribute to understanding the previously unexplained reproductive success of subordinate male chimpanzees

Acoustic communication and behaviour of the golden haired pine bark beetle, Hylurgus ligniperda (Coleoptera: Curculionidae) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Zoology at Massey University, Palmerston North, New Zealand

The golden-haired bark beetle, Hylurgus ligniperda (Coleoptera: Curculionidae: Scolytinae) imposes significant threats to New Zealand pine log exports. To date, control strategies against this invasive insect have relied heavily upon fumigation treatments. However, novel environmentally friendly and cost-effective strategies that decrease reliance on fumigants and can be used as part of an integrated package of disinfestation methods are urgently needed. The adults of H. ligniperda produce characteristic and species-specific sounds when disturbed or aggregated. Males produce distinct audible simple and interrupted chirps using an elytral abdominal stridulatory mechanism whereby the pars stridens, usually present on the left elytrum, are scrapped by the sclerotized pegs present on the seventh segment of the abdominal tergite, whereas the females (despite having a similar stridulatory mechanism) just produce a click-like sound. Although the ability to produce sounds by H. ligniperda has been acknowledged for decades, nothing is yet known as to the relevance of acoustics on the behaviour of this species. Thus, the main objective of this thesis was to study the sound-related behaviours of H. ligniperda under various scenarios (i.e. distress, mating, competition territoriality and colony) and to investigate the functions and characteristics (temporal and spectral) of the acoustic signals produced by this insect and their role in intraspecific communication. Our results indicate that the role of sound in communication in the case of H. ligniperda is oriented more towards communication between the sexes rather than within individuals of the same sex. Depending upon the scenarios studied, the males of H. ligniperda can produce different frequencies of acoustic signals, ranging from 232 Hz to 21890 Hz. The minimum and maximum amplitudes of male acoustic signals (chirps) were highest in a colony context (-661270 and 764270), and lowest during competition (-12633 and 190383). The males did not produce any sounds (chirp) during mating. Similarly, the spectral analysis indicated that the females can produce acoustic signals of different frequencies in the range from 256 Hz to 23875 Hz. The minimum and maximum amplitudes of the female acoustic signals (clicks) were highest during competition (-189034 and 1041600) and lowest when they were distressed (-275112 and 191270). Toothstrike duration for male chirps (0.047 sec) and click duration for female clicks (0.012 sec) were longest when the beetles were distressed. When distressed, the males produced a significantly higher number of simple chirps with a longer chirp duration and higher toothstrike rate. Similar patterns were observed for distressed females, that produced significantly higher number of clicks with a longer click duration. The role of interrupted chirps for distressed males was minor. However, in a mating context, the interrupted chirps seemed to play a more significant role in communication than the simple chirps. Courtship displays were carried out by the males when the female was a virgin and never occurred when the female was already mated by a different male. The duration of the courtship displays was affected by competition between males. Mating time was also affected by the presence of competing males. When there were no males competing for a female in a mating trial, the duration of the courtship and of the mating was found to be comparatively longer than in the presence of competing males. Although H. ligniperda was previously reported as a monogamous species, the observations of this thesis indicate that this insect is a polygamous species with the ability to mate multiple times with multiple partners. This study provides a good example of acoustics research in insects and a proof- of-concept for future research on acoustics as a deterrent or behaviour-modifying tool for H. ligniperda control

Adaptive female choice for middle-aged mates in a lekking sandfly

Most theoretical models of age-related mate choice predict that females should prefer older males because they have proven survival ability. An alternative view is that older males represent inferior mates because of negative genetic correlations between early and late fitness components, or because older males have traded off longevity against other fitness components, have accumulated deleterious germ-line mutations, or are less well adapted to current conditions than more recently born individuals. While numerous studies have reported female choice for older males, few have explicitly examined the fitness consequences of such a preference. We present evidence from a lekking sandfly, Lutzomyia longipalpis , showing that choosy females discriminate against older males and gain a fitness benefit from their choice. When permitted free choice from an aggregation consisting of males aged zero to two days (young), four to six days (middle-aged) and eight to ten days (old), females preferentially mated with middle-aged males, but all measures of female reproductive success were independent of male age. In contrast, when a second set of females was randomly assigned single virgin males of known age, the eggs of those paired to old mates exhibited lower hatching success than the eggs of females mated to young or middle-aged males. These results suggest that females avoid mating with older males because they represent poorer quality mates. Age-related differences in male quality may have a genetic basis, but could equally well arise through a phenotypic decline in sperm quality or sperm transfer ability with male age. The lack of evidence of female discrimination against older males from other studies may be because these did not explore the reproductive success of the full age range of males