Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 18 of 18 for “"sperm competition"”.
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Sperm Competition and the Function of Masturbation in Japanese Macaques (Macaca fuscata)
… is in direct contrast to established theories of sperm competition, which predict that species with a higher risk of sperm competition (i.e. those with multi-male multi-female breeding systems) should invest in large ejaculate volumes so as to out-compete conspecifics. They should not, therefore, …
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Sex in southern african spirostreptida millipedes : mechanisms of sperm competition and cryptic female choice
… They are polygynandrous. Males transfer sperm via species-specific accessory genitalia called gonopods, that comprise three components, two of which, the emote and telopodite, are involved in processes of sperm transfer. The emotes function to translocate ejaculates from the penes to the …
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Selected elements in Lake Michigan round goby (Neogobius melanostomus) reproductive physiology: spawning effort and determination of reproductive status of females and sperm competition in two reproductively distinct male morphs
… of reproductive status of female round goby and sperm competition in two alternative reproductive tactics of male round goby in southwestern Lake Michigan. Spawning peaks differed between two relatively proximate sites and occurred at 14-17°C. Peak spawning effort as determined by Gonadosomatic …
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Unravelling the ecological trade-offs in behavioural and physiological sexual traits
… will have direct impacts on the risk of mate competition and the opportunity for mate choice. At the same time, biotic environmental changes in the environment could have impacts on nutritional availability, and therefore the condition state of individuals.<br/><br/>In Drosophila melanogaster, …
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Mating dynamics of South African forest millipedes : Centrobolus (Diplopoda: Pachybolidae)
… two most common mechanisms of sexual selection, sperm competition and cryptic female choice. The approach was to (1) quantify sexual dimorphism and find the selection pressures operating on the sexes, (2) determine the functional significance of male and female genitalia, (3) understand why there …
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Sperm utilization patterns in Gryllus integer (orthoptera: gryllidae
Sperm competition is the competition for fertilizations between ejaculates, within a female, following multiple mating. There are four sperm utilization or precedence patterns: first male precedence, where the first male to mate fertilizes most of the eggs laid by a female; last male precedence, …
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Mechanisms and consequences of hybridisation between Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)
… investigate mechanisms of hybridisation through sperm-egg interactions, much of which is poorly understood. Salmon and trout experience conspecific sperm precedence during in vitro sperm competition experiments, when sperm volumes and release times are equalised. This thesis firstly aimed to …
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The adaptive significance of multiple mating by males in the polygynandrous waterstrider Aquarius remigis (Heteroptera: Gerridae)
In polygynandrous species, sperm competition and female post-insemination processes may influence male paternity success. Hence, insemination (i.e. successful sperm transfer) may not guarantee reproductive success for the male. Using a variation of Parker's (1970) sterile (irradiated) male …
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Sisters' curse: sexually antagonistic selection constrains the spread of a rare mitochondrial haplogroup
… numbers of small and physiologically inexpensive sperm. This differential investment in gametes has long been identified as a force driving the evolution of divergent mating tactics in the sexes. In most species, anisogamy is also coupled with strict maternal inheritance of genetic elements in the …
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Mating costs and gametic barriers to reproduction
… isolation using 10 different species. This sperm mediated form of gametic isolation likely evolved from intra-species sperm competition, resulting in incompatibilities as a byproduct of competitive sperm in inter-species matings that caused early death, sterility, and invasive sperm. I …
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Male gamete morphology in relation to swimming velocity and fertilisation microenvironment
The heterogeneity of spermatozoa has been widely used to inform phylogenetic relationships among taxa, yet the reason such diversity has evolved, in relation to the sperms primary functional role in fertilisation and reproduction, is not well understood. Research into the evolutionary significance …
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An Assessment of the Effects of Sexual Selection and the Social Environment on Mating Behaviors in Two Tiger Beetle Species (Coleoptera: cicindelidae)
… by males of many species that results due to sperm competition. Facultative mating behaviors are predicted to occur in these taxa when changes in the social environment alter the benefits for guarding males. I used field observations and lab experiments in 2006 and 2007 to investigate the …
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Function and evolution of seminal fluid components in Drosophila
… conflicts such as male-female sexual conflict, sperm competition, and cryptic female choice. These forces have driven rapid diversification of reproductive molecules across species, with lineage-specific gains, losses, and gene duplications shaping the complement of reproductive fluids. Despite …
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The evolution of mating systems in black scavenger flies (Diptera: Sepsidae)
… females. In a study of the patterns of sperm precedence in one sepsid species, I found that the sepsids' peculiar timing of matings is not associated with unusual patterns of sperm precedence: sepsid males displace rival sperm and achieve a large last male advantage, which is the most …
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The biology of Boopsoidea inornata (Castelnau, 1861) and life history comparisons within the Sparidae
… is a resident, group-spawner, engaging in sperm competition. R. globiceps is a moderately long-lived migrant with a sex ratio of 1:1, that also engages in sperm competition over a short spawning season. B. inornata is a polygamous, long-lived resident with low annual fecundity, but a …
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Sex-specific reproductive strategies in redfronted lemurs (Eulemur fulvus rufus, Primates, Lemuridae)
… a group of females. Due to male intrasexual competition, the sex ratio of groups of anthropoid primates is generally female-biased. Gregarious Malagasy lemurs deviate from theoretical expectations derived from sexual selection theory and from patterns found among anthropoids because they live …
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Biochemical and physiological changes in bovine sperm during extended incubation under aerobic and anaerobic conditions
… damage eventuating in the loss of fertility of sperm cells. This has been known for many years and current production systems for storage of semen in the liquid state attempt to minimise oxidative stress. This is achieved by reducing oxygen tension in the diluent through nitrogen gassing and by …
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Strategies of Sexual Reproduction in Aphids
… Blattläusen zur Verfügung stehende Menge Sperma limitiert ist. Des weiteren wird Ejakulat von vorherigen Paarungen anscheinend nicht verdrängt, so dass die Kapazität der Weibchen, weiteres Sperma zu speichern, ebenfalls begrenzt ist. Diese Vermutung bestätigend wird das Sperma von U. …