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<p>Agronomic management decisions are made to maximize plant growth and crop yields but can also be used as tools to manage insect pests. Different management practices, such as nitrogen fertilization, cultivar selection, and planting date choice can influence the foliar traits of a crop. Plant foliar traits play important roles in mediating plant-herbivore interactions. Herbivores balance consumption of plant tissue for nutritional gains while contending with plant traits that may deter herbivory or are toxic. Agronomic management practices have been widely studied in many crops, however, for a new or re-emerging crop, there is less information on the influence management has on insect herbivory. Industrial hemp (<i>Cannabis sativa</i> L.) is a re-emerging crop in the United States that is gaining interest, but the current literature has not clearly defined the influence different management practices can have on hemp foliar traits and the role foliar traits play on hemp-insect interactions. The goal of this study was to understand the influence management strategies and temporal changes have on hemp morphological and chemical foliar traits and how these differences alter herbivore performance. </p> <p>To understand the influence of management practices on hemp foliar traits and insect performance, I conducted both greenhouse and field herbivory studies using field grown hemp in both cases. In 2017 leaves from three different field-grown hemp cultivars, were planted on two different dates, and received two different rates of nitrogenous fertilizer and were then used for a no-choice feeding bioassay using fall armyworm (<i>Spodoptera frugiperda</i>). Foliar nitrogen, C:N, LMA, THC, and CBD were determined and insect performance was measured as growth, consumption, and frass production. Management practices influenced the foliar traits of hemp, specifically fertilization rate, cultivar, and the interaction of fertilization rate with cultivar and with planting date altered foliar traits. Fertilization rate had the greatest influence on herbivore performance, driven by higher foliar nitrogen. Foliar nitrogen had a strong positive influence on insect performance and the ratios of carbon to nitrogen and total cannabinoids to nitrogen had strong negative influences on insect performance. </p> <p>To measure foliar trait changes over the course of a growing season in different cultivars and to determine herbivore damage, three hemp cultivars were planted in 2018, and leaves were collected at five time points to measure changes in foliar traits. To measure herbivory, leaves were collected at the end of the 2018 growing season and percentage of tissue removed by herbivores was calculated. Foliar traits changed across the growing season, with a decrease in foliar nitrogen and an increase in the ratio of carbon to nitrogen, leaf thickness, THC, and CBD. The foliar trait that had the strongest positive influence on herbivore damage was foliar nitrogen, and higher nitrogen was associated with more herbivore damage. C:N, LMA, and ratio of total cannabinoids to nitrogen had strong negative influences on herbivore damage. Both studies can give us insight into the foliar traits that are driving hemp-insect interactions. Because foliar nitrogen had the greatest positive influence, while the ratios of carbon to nitrogen and total cannabinoid to nitrogen had the greatest negative influence on both performance and field herbivory, focusing on management that affects these three foliar traits is important for pest control. Since foliar nitrogen, C:N and total cannabinoids:N were all affected by nitrogen fertilization, reducing the amount of nitrogenous fertilizer applied while still considering yield could be and important management tool to reduce insect pests. </p>

This study doubles the known diversity of nemertean species in one region along the northeast Pacific coast by utilizing the often over-looked larval life-history stage. Prior to this work, the nemertean fauna in this region was believed to be well described; however, previous assessments were based on adult life-history stages only and significantly underestimated the real diversity. With this dissertation, we update what is known about nemertean diversity and expand upon this “life-history” approach to describe new species, identify and describe larval forms, and speculate on the phylogenetic relevance of nemertean larvae. A considerable amount of new diversity takes the form of cryptic species complexes, where existing descriptions include characteristics of several species. Micrura alaskensis, a common intertidal nemertean and an emerging model system for developmental studies, existed as a species complex consisting of five species. In this dissertation we designate a new genus, re-describe M. alaskensis, and describe four new species in this complex. In doing so we make accurate identification possible for future comparative research. The complete development of few nemertean species was known before this project began, thus few species could be identified as larvae. We have identified over 30 nemertean larvae using both embryological and DNA barcoding approaches in this work. Intriguingly, many wild-caught larvae could not be matched to species previously reported from this region and instead contribute to previously unknown diversity. This new diversity includes species previously reported only from distant geographic regions as well as species new to science. The first record of a hubrechtid on the west coast of North America and the identification of two new species in the currently monotypic genus Riserius were revealed in larval assessments. Aside from increasing known species-level diversity, we revealed novel larval types. Barcoding larvae allowed us to place larval morphotypes into a phylogenetic context and identify potentially useful larval synapomorphies for nemertean phylogenies. Our results emphasize the importance of a life-history approach to biodiversity assessments for all species with biphasic life-cycles. This dissertation includes published and unpublished co-authored material.

Nototodarus sloanii is an important component of the Southern Ocean fauna, and the basis of a large commercial fishery. Despite this, much is unknown about the biology of this species. This study examines some aspects of the biology of N. sloanii. Stomach contents analysis identified no significant differences in diet between male and female squid. Sixteen putative species, including 12 identifiable teleosts, 2 crustaceans, and 2 cephalopods were identified in the diet of this species. The euphausid, Nyctiphanes australis was the most important prey item, Lanternfish, Lampanyctodes hectoris, and Pearlside, Maurolicus muelleri, were of secondary importance. Squid were aged using counts of statolith micro-increments and back-calculation from the date of capture showed that hatching occurred between August and February, with a peak in the austral winter/spring and another smaller peak in the austral summer. Growth rate for male squid differed depending on whether squid were hatched in the winter/spring or summer. Growth rates were more variable in the winter/spring-hatched individuals, and they attained larger size than summer-hatched squid. This was not the case for female squid. Mean age for immature winter/spring-hatched squid was significantly higher than for summer-hatched squid, although there was no significant difference in mean mantle length or body mass. No significant differences between mean age, mantle length, or body mass for same-gender mature squid, regardless of hatch season, were apparent. However, mature female squid hatched in the winter/spring season were significantly longer (ML) than mature male squid hatched in winter/spring. No squid was found to be older than 211 days. All squid had started to mature by 91-120 days old and all were fully mature at 180 days. Validation experiments run on juvenile squid using calcein markers were inconclusive, however the increments in the statoliths were very similar to those found in other validated species of ommastrephid squid, thus for the purposes of this study they were assumed to be of daily periodicity. Gladius increments identify a gender difference in growth rate, with female squid having a shorter initial slow growth phase than male squid. Gonadosomatic indices (GSIs) were calculated for male and female squid. These were low (7.12%�0.3% for females and 1.9%�0.2% for males) suggesting that these squid are intermittent spawners. This is further supported by a histological examination, which found germinal cells of different stages present in the same gonad. Lack of mature individuals in this study means that these results are suggestive rather than definitive; more examination of the reproductive process of this squid is required. Histological examination was also used to validate the Lipinski maturity scale for use with this species, while some misidentification occurred the scale is useful to place squid into the broad categories of immature, maturing, or mature. New maturity scales were created for N. sloanii utilising these broad categories. Finer-scale identification is not possible using this scale, as maturation appears to be a continuous process. Morphometric measurements were taken from both hard and soft tissues and were analysed using non-metric multidimensional scaling and analysis of similarity. Divisions were only apparent in the hard structure measurements. They did not appear to be age, dietary or reproductive differences.

Thesis (M.S.)--Ohio University, June, 2006. / Title from PDF t.p. Includes bibliographical references (p. 97-104)

The role of inhibitory compounds such as adenosine and GABA in modulating neuronal activity in invertebrate species is not well described. Here I investigate their role in modulating excitability of cluster F neurons in the pedal ganglia of Lymnaea stagnalis. Receptor-specific agonists and antagonists were used to determine that the inhibitory effects of adenosine were mediated through the adenosine A1 receptor, and that action potential frequency varied linearly with intracellular calcium concentrations. These effects had a seasonal dependence, as neurons were resistant to adenosinergic modulation during the summer months. GABAergic modulation of neuronal activity was also seasonal as demonstrated by ionic plasticity in GABAergic transmission. GABA application led to inhibition or excitation of electrical activity in neurons obtained during the fall and winter months, respectively. These effects were mediated through the GABA(A) receptor because of sensitivity to GABA(A) receptor antagonist bicuculline and were likely due to differential cation-chloride cotransporter activity.

The role of inhibitory compounds such as adenosine and GABA in modulating neuronal activity in invertebrate species is not well described. Here I investigate their role in modulating excitability of cluster F neurons in the pedal ganglia of Lymnaea stagnalis. Receptor-specific agonists and antagonists were used to determine that the inhibitory effects of adenosine were mediated through the adenosine A1 receptor, and that action potential frequency varied linearly with intracellular calcium concentrations. These effects had a seasonal dependence, as neurons were resistant to adenosinergic modulation during the summer months. GABAergic modulation of neuronal activity was also seasonal as demonstrated by ionic plasticity in GABAergic transmission. GABA application led to inhibition or excitation of electrical activity in neurons obtained during the fall and winter months, respectively. These effects were mediated through the GABA(A) receptor because of sensitivity to GABA(A) receptor antagonist bicuculline and were likely due to differential cation-chloride cotransporter activity.

This study combined sedimentation, sediment chemistry and benthic community data from three Oncorhynchus mykiss cage farms in Ontario, along with a laboratory bioassay to examine the effects of aquaculture waste loading. Waste loading rates, as well as sediment TC, TN, TP and metal (Cu, Zn) concentrations were highest beneath the cage and decreased exponentially with distance. During the 21-day bioassay, Tubifex (Oligochaeta, Naididae), Chironomus (Diptera, Chironomidae) and Sphaerium (Bivalvia, Pisidiidae) were subjected to a gradient of waste loading. Survival and growth of Sphaerium simile was highest at intermediate levels of waste loading. Chironomus riparius growth increased with increasing waste addition. Tubifex tubifex growth increased with exposure to fish waste, compared with the control. Until this study, there were no predictions for thresholds of effect at freshwater cage farms in the literature. The proposed threshold of effect on freshwater benthos is 2.0 - 3.0 g C m-2 day-1.

Many stream restoration projects, as part of returning a degraded ecosystem to a healthier state, aim to restore aquatic invertebrate populations. Unfortunately, many attempts only „beautify‟ streams without achieving improvements in biodiversity. Lack of connectivity of a restoration site to a regional species pool may explain some failures. I tested this by collecting larval and adult aquatic insects from an agriculturally impacted Canterbury high country stream to evaluate connectivity of the regional species pool. The stream was surrounded by high-quality habitat in an adjacent National Park. Surrounding streams contained diverse assemblages of aquatic insects, but processes in the environment and limitations of in-stream habitat meant their adults did not always arrive at the target. In addition, oviposition habitat for hydrobiosid caddisflies was added to sections of stream and compared to un-manipulated control sections to test oviposition site limitation. The addition of oviposition habitat led to more hydrobiosid egg masses in comparison to control reaches. However, oviposition was also limited by in-stream habitat conditions, particularly the abundance of fine sediments. Sedimentation is a common pollutant in streams and is linked to decreases in habitat, food resources, and invertebrate populations. Moreover, common restoration methods, such as riparian management, have little success at reversing already high sediment levels, and are therefore insufficient to bring improvements to in-stream communities or sought-after habitat conditions. Therefore, after determining sediment was restricting sensitive invertebrate recovery at Riversdale Stream, by adding patches of high quality habitat I experimentally compared the factorial effects of sediment flushing and channel narrowing on sediment removal. Treatments improved habitat and prompted recovery of sensitive invertebrates, but an interactive effect where both flushing and channel narrowing combined created the most improved habitat conditions and the greatest improvements of invertebrate communities. Thus, while habitat improvements are an important part of restoration, features limiting species recovery such as connectivity and sedimentation, are particularly important.