A new macroscopic ovarian reproductive maturity index for haddock, Melanogrammus aeglefinus L, was developed to improve field collection of reproductive stage data. The index was tested, validated and revised based on a comparison with a laboratory histological staging method. The comparison of field and histological observations helped to improve the field index and methodologies and provided useful insight into the reproductive biology of Haddock. Although laboratory staging based on histology is inherently more accurate than any macroscopic field staging method, field observations can reveal weaknesses in the laboratory approach due to sampling bias. The revised field index includes three new macroscopic stages that represent a progression in final oocyte maturation from early to late, which were found to be reliable for staging spawning readiness in the field. This index was then used to study a population of Haddock in the Gulf of Maine to determine if it exhibits diel spawning periodicity. Commercial fishing vessels were chartered for 25 dedicated longlining trips to collect sexually mature haddock in the Southwestern Gulf of Maine at locations identified by commercial fishers as having spawning aggregations. In order to examine diel effects on haddock reproduction, the change in catch per unit effort and percentage of male and female haddock of all reproductive maturity stages together with the gonadosomatic index were observed across a 24 hour diel cycle. Only females in hydration stage 3 (defined as late final oocyte maturation stage ovaries with 50-75% of oocytes hydrated) were significantly affected by time of day with significant increases in both catch per unit effort and percentage of hydration stage 3 haddock during the night. Because H3 is the most advanced reproductive stage observed prior to a spawning event and therefore the best indicator of imminent spawning these results demonstrate that female haddock in Southwestern Gulf of Maine primarily spawn during night hours with a peak between 2100 and 0100 hours. No diel trend was observed for any male reproductive stages. Additionally, no diel trend was observed in male or female reproductive stages unrelated to spawning including immature, spent and resting.

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Aedes aegypti mosquitoes are found globally and also act as the primary vector of Zika, dengue, and Chikungunya viruses, for which there are limited treatment options and no vaccines available. The use of insecticides as the main control strategy against diseases transmitted by this mosquito, is increasingly challenged by emerging resistance. Thus, there is a dire need for the development of novel approaches informed by an improved understanding of mosquito biology, to control mosquito populations and, ultimately, disease transmission. Rhythmic biological processes in mosquitoes help optimize resource exploitation by coordinating behaviors and physiology with fluctuating environmental conditions. Such synchronization enables organisms to adjust their physiology, metabolism, and behavior to predictable external cycles. In mosquitoes, circadian rhythmicity has been demonstrated in their biting and oviposition behavior, as well as their locomotor activity. However, little is known regarding how responses to long-range host cues are modulated by the circadian system. Here we show that both antennal sensitivity and olfactory behavior are time-of-day and odor-specific in Ae. aegypti females. Global transcriptomic analysis in whole heads of Ae. aegypti females reveal chemosensory genes differentially expressed throughout the day, providing insight into the molecular mechanisms behind daily variations in olfactory sensitivity and behaviors. We additionally show an odor-induced activation of mosquito behavior. Mosquito locomotion and behavior are also mediated by physiological state, and activity decreases after blood-feeding. Since the central clock components have been shown in other organisms to be redox-sensitive, we explored the role that diet heme plays in mediating behavioral changes following blood ingestion using artificial blood diets. We found that the transcription of the timekeeping gene period is reduced in the head immediately after feeding on a meal containing hemoglobin, but peripheral period transcription is reduced throughout the course of digestion following ingestion of a protein meal independent of hemoglobin inclusion. Overall, our results show that Ae. aegypti behavioral rhythms mediated by rhythmic gene expression are plastic and susceptible to external host cues and host blood digestion. This work can be leveraged for future studies investigating mosquito host-seeking and blood digestion to identify novel targets for vector control. / Doctor of Philosophy / Female mosquitoes rely on blood-feeding in order to produce eggs, but can unfortunately act as vectors of disease if they transmit pathogens when biting. Insecticides are currently our strongest main tool for controlling mosquito disease vectors such as Aedes aegypti, the yellow fever mosquito. However, increasing cases of insecticide resistance present new challenges in vector control, and new strategies to prevent vector-borne disease are needed. The Ae. aegypti mosquito is found globally and transmits Zika, dengue, and Chikungunya viruses, for which there are limited treatment options and no vaccines available. Mosquitoes exhibit rhythms in their gene expression and behaviors such as biting and activity patterns, in order to optimize energy efficiency and coordinate their biology and behaviors with daily fluctuations in the environment. However, it is unknown how their responses to human host odor cues are modulated by their central timekeeping system in the brain. Mosquitoes primarily find a human host via their sense of smell, or olfaction. Odor molecules in the air, emitted by humans, can be detected by mosquitoes' antennae. Here we show that both antennal sensitivity and behavioral responses to odors are time of day and odor-specific in Ae. aegypti females. We quantified gene transcripts in whole heads of Ae. aegypti females as a measure of gene expression, which revealed that genes involved in odor detection are expressed differently throughout the day, providing insight into the molecular mechanisms behind behavioral observations. We also show that mosquito behavior can be activated by odor exposure, and that their behavioral patterns can be influenced for multiple days following exposure. Mosquito behavior is also influenced by blood-feeding, which reduces mosquito activity and flight. Time-keeping genes in the fly brain have been shown to be sensitive to oxidative stress. Blood contains the protein hemoglobin, which can lead to oxidative stress when digested. Using artificial blood diets that allowed us to include or exclude hemoglobin in the meal, we found that the transcription of the timekeeping gene period is reduced in the head immediately after feeding on a diet containing hemoglobin, but is reduced in the rest of the body throughout the course of digestion following ingestion of a protein meal, whether hemoglobin was included or not. This work can be leveraged for future studies investigating mosquitoes' rhythms in host-seeking and blood digestion to identify new effective targets for vector control.

Predicting the impacts of non-native species remains one of the greatest challenges to invasion ecologists. Because of their insularity, freshwater systems are particularly vulnerable to invasions, especially from non-native predators. The research in this thesis explores the role of abiotic and biotic factors in mediating the distribution and impact of Bythotrephes longimanus, a predatory cladoceran that has been introduced to freshwater systems in North America. Although the general impacts of this invasion have been documented, little is known about the factors that modulate them. Using a combination of field surveys and experiments, I tested several hypotheses concerning the influence of interactions with native species, as well as the role of heterogeneity in the light environment, in mediating the impact of Bythotrephes. Results demonstrated that biotic resistance by native macroinvertebrate predators does not play a limiting role in the establishment success of Bythotrephes. However, the within-lake distribution of Bythotrephes was influenced by these macroinvertebrates, suggesting that the native predator context matters when trying to understand the impacts of non-native predators. This was demonstrated with a mesocosm experiment in which the impact of Bythotrephes was constrained by the native Chaoborus larvae. In terms of the abiotic environment, in situ feeding experiments demonstrated that refuges from impact could exist for some prey taxa, as the outcome of predation by Bythotrephes was dependent on light availability and some prey taxa were more successful at evading predation under low light conditions. Finally, results show that adaptive behaviour by prey is also an important determinant of impact, as migrating Daphnia can escape predation effects by Bythotrephes. The combination of light-limited predation and a shallow distribution by Bythotrephes selects for prey that occupy relatively deeper positions during the day. As a whole, this research highlights the importance of complex interactions in mediating the impact of Bythotrephes and may help to explain some of the variation that has been documented among invaded lakes. A better understanding of these complex interactions can improve our ability to anticipate impacts as Bythotrephes continues to spread, as well as provide insight on some of the long-term effects following invasion. / Thesis (Ph.D, Biology) -- Queen's University, 2013-06-17 09:26:35.221

The main theme of this thesis is the interactions of animals with the environment and each other. The thesis was written within the framework of a biomanipulation project “Pikeperch in Himmerfjärden”. With the aim to investigate possible trophic pit-falls, give the manipulation the best possible start, and find ways to monitor the progression of the manipulation. In Paper I the diet of the invader cladoceran Cercopagis pengoi is analysed with stable isotopes; conducted prior to stocking. C.pengoi has a preference for large copepods, indicating possible competition with fish. Paper II investigates the behavioural differences between pikeperch fingerlings reared in different environments (pond vs. tank). Results suggest that fish reared in semi-natural ponds are more likely to survive directly after stocking. In Paper III and IV, the diel vertical migrations (DVM) of copepods are in focus. In Paper III the migrations of two copepod species: Acartia spp. and Eurytemora affinis are studied over season and life stage. The amplitude of migration was found to increase with ontogeny for both species, indicating evasion of visual predators. Paper IV examines the varying migratory patterns of adult female E. affinis finding that these animals migrate more actively when feeding conditions deteriorate and growth decreases. The overall conclusions of the thesis are that behavioural, not only direct trophic interactions are key when studying ecosystems. / <p>At the time of the doctoraldefense, the following papers were unpublished and had a status asfollows: Paper2: In press. Paper 4: Manuscript.</p>

In this study, the factors influencing zooplankton community structure in Turkish shallow lakes were elucidated with four main approaches: (i) space-for-time substitution for shallow lakes using snap-shot sampling in 31 lakes along a latitudinal gradient / (ii) in-situ mesocosm experiments in eleven lakes along a latitudinal gradient using three sets of artificial plants systems / (iii)&lsquo / Habitat Choice&rsquo / laboratory experiments mimicking a &lsquo / shallow littoral&rsquo / zone with plants and a &lsquo / deeper pelagic&rsquo / zone with sediments testing the response of Daphnia magna to predation cues / and (iv) long-term monitoring data (1997-2011) from two interconnected lakes. Snap-shot and long-term monitoring showed that eutrophication has a strong influence on the zooplankton community via increased fish predation, nutrient loading and salinization. Here too the zooplankton community shifted towards a smaller sized profile, especially in lakes located at lower latitudes. Moreover, The laboratory and in-situ mesocosm experiments revealed that under predation risk Daphnia preferred to hide near sediment instead of using submerged plants as a refuge. Accordingly, in-situ mesocosm experiments revealed a predation pressure induced size structure shift towards small-medium sized zooplankton and calanoid copepods. The long-term monitored lakes experienced (i) drought-induced water level drop, leading to increased salinity and eutrophication, and consequent anoxic conditions and fish kill / as well as (ii) biomanipulation in the downstream. Both conditions resulted in major reduction in the top-down control of fish and ultimate predomination by large sized Daphnia spp. Nevertheless, the excessive exploitation of lakes and ongoing warming entail Turkish shallow lakes to become more eutrophic, making this study indicative for the Mediterranean region.

Lake Winnipeg has been subject to intense eutrophication and invasive species such as Rainbow Smelt and Eubosmina coregoni for the last 40 years. This study demonstrated significant increases in total phosphorus, total nitrogen, chlorophyll-a, overall zooplankton abundance, and specifically Cladocera, between 1969 and the first decade of the 21st century. There were specific basin differences in the long-term changes of the Cladocera community, with the species Chydorus sphaericus and Ceriodaphnia quadrangula negatively affected by high levels of phosphorus, nitrogen and chlorophyll-a. Moreover, long-term change in the Cladocera community composition and abundance throughout the years (1969-2011) during summer was correlated with intensifying eutrophication. Additionally, weak diel vertical migration in the zooplankton community was observed for the first time in Lake Winnipeg.

Lake Winnipeg has been subject to intense eutrophication and invasive species such as Rainbow Smelt and Eubosmina coregoni for the last 40 years. This study demonstrated significant increases in total phosphorus, total nitrogen, chlorophyll-a, overall zooplankton abundance, and specifically Cladocera, between 1969 and the first decade of the 21st century. There were specific basin differences in the long-term changes of the Cladocera community, with the species Chydorus sphaericus and Ceriodaphnia quadrangula negatively affected by high levels of phosphorus, nitrogen and chlorophyll-a. Moreover, long-term change in the Cladocera community composition and abundance throughout the years (1969-2011) during summer was correlated with intensifying eutrophication. Additionally, weak diel vertical migration in the zooplankton community was observed for the first time in Lake Winnipeg.