Biology

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Open Access
A Chironomid-Based Paleolimnological Assessment of Long-Term Cumulative Effects Of Multiple Anthropogenic Stressors on Hypolimnetic Oxygen Dynamics in Lake Erie
(2018-08-27) Perlov, Dmitri; Quinlan, Roberto
The central basin of Lake Erie is annually subjected to hypoxia, which has implications for fish communities and nutrient recycling. As limnological monitoring data for Lake Erie does not extend beyond the 1970s, paleolimnological techniques can be used to reconstruct long-term water quality trends. Chironomidae (Diptera) remains preserved in dated sediment cores from the western, central, and eastern basins in Lake Erie were used to assess the long-term cumulative effects of multiple anthropogenic stressors on hypolimnetic dissolved oxygen. Results from analyses of subfossil chironomid remains indicated that the central basin has exhibited mesotrophic to eutrophic conditions since 1850. However, a transition in chironomid communities further towards anoxic-type taxa between 1930-1950 suggests that the severity and duration of hypolimnetic anoxia has increased in recent decades. Variance partitioning analysis (VPA) indicated that the effects of land use and climate had significant implications in driving changes in chironomid assemblages in the central basin.
Open Access
A non-canonical role for p107 in muscle stem cell fate decisions
(2024-03-16) Hsiung, Justin Wei-Liang; Scime, Anthony
The regenerative potential of skeletal muscle is attributed to the presence of resident muscle stem cells known as satellite cells (SCs). After activation SCs have two fates, either to differentiate into new muscle or self-renew to replenish their population. Dysregulation in favor of one outcome over the other has been implicated in loss of muscular regenerative capacity. Mitochondrial metabolism has recently emerged as a regulator of SC fate decisions. We uncovered a non-canonical mitochondrial role for retinoblastoma-like protein 1 (Rbl1, p107) in manipulating fate decisions through its effect on mitochondrial dynamics. We find that in the absence of mitochondrially localized p107, SCs display a higher rate of self-renewal, while also exhibiting higher mitochondrial connectivity. This was associated with increases in the mitochondrial fusion protein OPA1, as well as a loss in cellular acetylation. Taken together, these findings suggest that non-canonical p107 function in SCs controls their cell fate decisions.
Open Access
A Revision of Chilicola (Heteroediscelis), A Subgenus Endemic to Chile
(2015-12-16) Monckton, Spencer Kelvin; Packer, Laurence
The bee subgenus Chilicola (Heteroediscelis) Toro & Moldenke, 1979 (Colletidae: Xeromelissinae) is revised. Seven new species are described: Chilicola (Heteroediscelis) charizard Monckton sp. nov., Chilicola (Heteroediscelis) curvapeligrosa Monckton sp. nov., Chilicola (Heteroediscelis) guanicoe Monckton sp. nov., Chilicola (Heteroediscelis) lickana Monckton sp. nov., Chilicola (Heteroediscelis) mayu Monckton sp. nov., Chilicola (Heteroediscelis) packeri Monckton sp. nov., and Chilicola (Heteroediscelis) randolphi Monckton sp. nov. Nine of the ten existing species are redescribed and Chilicola (Heteroediscelis) valparaiso Toro & Moldenke, 1979 syn. nov. is treated as a junior synonym of Chilicola (Heteroediscelis) mantagua Toro & Moldenke, 1979. Keys to species for males and females are provided, along with habitus images, images of male terminalia, and distribution maps for each species. Results of phylogenetic analyses are presented, based upon 61 morphological characters and CO1 barcode sequences. Monophyly of the subgenus is supported, and groupings within it are briefly discussed in the context of geographic distributions.
Open Access
A Role for Fenugreek in Altering the Osmoregulatory Capacity in Rainbow Trout (Oncorhynchus Mykiss)
(2015-12-16) Mckee, Sean Dylan; Kelly, Scott Phillip
Fenugreek (Trigonella foenum-graecum) is a botanical galactogogue that has been shown to increase milk production and serum prolactin in mammals. Prolactin is classically considered to be a freshwater-adapting hormone in teleost fishes. If fenugreek promotes prolactin synthesis, then it has the potential to decrease perturbations associated with exposure to hypoosmotic conditions in fishes. To test this, rainbow trout (Onchorhynchus mykiss) were fed doses of fenugreek, and endpoints of ionoregulatory ability were assessed. A single dose was used in a hypoosmotic stress experiment. Fenugreek did not disrupt systemic endpoints of salt-and-water balance. Transcript abundance of prolactin receptor in the gill and hypothalamus, and corticosteroid receptors in the gill decreased. Fenugreek resulted in an increase in claudin-7 and -30, and a decrease in claudin-33b. While it was demonstrated that fenugreek can impact salt-water balance, and affect changes similar to freshwater acclimation, it is unlikely that these changes were brought about via prolactin.
Open Access
A Role for p107 in Muscle Satellite Cell Self-Renewal
(2024-03-16) Shah, Vicky; Scime, Anthony
It is well established that skeletal muscle homeostasis is dependent on the activity of the muscle resident stem cells termed satellite cells (SCs). Many neuromuscular dystrophies and complications brought on from ageing are associated with decline to the SC population. Thus, there is a critical need to investigate the control mechanisms that dictate SC fate decisions for self-renewal that are crucial to maintain the SC population. A fundamental regulator of SC fate decisions is mitochondrial metabolism and thereby mitochondrial ATP generation via oxidative phosphorylation (OXPHOS). In our study we uncover a potential novel role for the transcriptional co-repressor retinoblastoma susceptibility protein like 1(Rbl1 or p107) in manipulating the self-renewal capacity of SCs through its mitochondrial localization under the control of the NAD+/NADH ratio. An investigation of this role for p107 function establishes a new mechanism to target SC decline and improve muscle regeneration that is required in muscular dystrophies and ageing.
Open Access
A Taxonomic Revision of Canadian Non-Osmia Osmiini (Hymenoptera Megachilidae)
(2018-03-01) Rowe, Genevieve Lauren; Packer, Laurence D. M.
The Osmiini (Hymenoptera: Megachilidae) is a tribe whose species encompass much of the biological diversity seen among bees (Michener 2007), and is one that contains many polytypic species in several genera. I use a molecular approach to taxonomy to test current morphological assessments of species-level diversity in the group, and herein examine all polytypic Canadian non-Osmia osmiine species. The analyses resulted in several taxonomic considerations in both the Ashmeadiella and Atoposmia groups. In addition, I present an up-to-date revision of Canadian non-Osmia Osmiini (Hymenoptera: Megachilidae). A key to the seven genera of Canadian Osmiini is provided and the 29 species of Canadian non-Osmia Osmiini are keyed, in dichotomous format for each genus, with all key features illustrated and full redescriptions of all species provided. Summaries of biogeographic distributions and life histories are included for each genus and its Canadian species.
Open Access
Abnormal Brain Connectivity in the Primary Visual Pathway in Human Albinism
(2016-09-20) Grigorian, Anahit; Schneider, Keith A.
In albinism, the ipsilateral projection of retinal axons is significantly reduced, and most fibres project contralaterally. The retina and optic chiasm have been proposed as sites for misrouting. The number of lateral geniculate nucleus (LGN) relay neurons has been linked to LGN volume, suggesting a correlation between LGN size and the number of tracts traveling through the optic radiation (OR) to the primary visual cortex (V1). Using diffusion data and both deterministic and probabilistic tractography, we studied differences in OR between albinism and controls. Statistical analyses measured white matter integrity in areas corresponding to the OR, as well as LGN to V1 connectivity. Results revealed reduced white matter integrity and connectivity in the OR region in albinism compared to controls, suggesting altered structural development. Previous reports of smaller LGN and the altered thalamo-cortical connectivity reported here demonstrate the effect of misrouting on structural organization of the visual pathway in albinism.
Open Access
Abnormal Lipid Signalling in the Developing Mouse Brain: Implications in Autism Spectrum Disorder
(2021-11-15) Rai, Ravneet; Crawford, Dorota Anna
Autism spectrum disorder (ASD) is a neurodevelopmental disorder, currently characterized by difficulties in social communication, delayed speech and language, and appearance of restricted and repetitive sensory-motor behaviours. Currently, there are many etiological factors, both genetic and environmental, that have been involved in its manifestation, including the lipid signaling pathway. The brain is rich in lipids, and the plasma membrane acts as a reservoir of bioactive molecules such as Prostaglandin E2 (PGE2), a lipid signaling molecule important for normal brain development and function. PGE2 is converted by cyclooxygenase-1 and -2 (COX-1 and -2) enzymes, a downstream action following release of arachidonic acid from the plasma membrane. Various genetic and environmental factors can influence the level of PGE2 and have been identified for their involvement in increased ASD-risk. However, the exact mechanisms behind this relationship are not well known, and thus the current dissertation aims to contribute to this gap in knowledge with four studies in vivo in the mouse brain. Using mouse models, we investigated the effects of maternal PGE2 administration (PGE2-injected) and gene knockdown of COX-1 and COX-2 enzymes (COX-1-/- and COX-2-/-) at E16 and E19, on sex- and age-dependent expression of developmental genes and proteins, global analyses of biological pathways, and characterization and analysis of dendritic spines morphology at P25. These studies established that aberrations in the COX/PGE2 signalling pathway result in differential expression of many genes and pathways involved in neurodevelopment and ASD etiology. We found abnormal age- (i.e. Mmp7 and Wnt2, Spn, Actb) and sex-dependent (i.e. Spn, Actb) gene and protein expression of developmental and synaptic functions, sex-specific enlargement of mushroom spines in cerebellar neurons, and ASD genes that are dysregulated throughout development (i.e. Glo1, Gabra2, Grm5). Interestingly, novel in vivo findings in mouse models of PGE2-administration and COX-2-/- (high and low levels) both confirmed an interaction between COX-2/PGE2 and Wnt pathway particularly at the E16 stage of development. The current findings strengthen the involvement of abnormal COX/PGE2 signalling during early brain development, and thus, many genes and environmental exposures during gestation can act on different constituents of the COX/PGE2 pathway, and result in neurological conditions such as ASD.
Open Access
An Analysis of the Affinity and Stability of Base Pair Modifications of the Glucose-Binding and Cocaine-Binding Aptamers
(2023-12-08) Osborne, Meghan Taylor; Johnson, Philip E.
Aptamers are selected to bind to their ligands, usually with high affinity and selectivity for targets. An aptamer was previously selected to bind glucose with a Kd of 10mM which is physiologically relevant as the blood glucose concentration typically falls between 4-11 mM. NMR spectroscopy is suited to study weak aptamer-ligand interactions and was used to investigate the affinity of sequence modified glucose-binding aptamers to try and determine a sequence with a greater binding affinity. Three of thirteen modifications bound to glucose, the change of a G-T base pair to a G-C base pair (Glumod-7) with a Kd of 2.9mM±0.3mM, the alteration of the terminal triloop from a C-T-C to a G-A-A (Gumod-8) with a Kd of 12mM±3mM, and the truncation by 3 base pairs (Glumod-12) which was too weak to determine a Kd. Glumod-7 was the only sequence which had a comparable Kd and would require further investigation in terms of stability using NMR thermomelts. Cocaine-binding aptamers are intriguing as they are composed of three stems centered around two mismatch A-G base pairs and are very well studied in terms of secondary structure and affinity. The thermostability of cocaine-binding aptamers as a function of number of base pairs in stem one was investigated by DSC. There was a trend observed of increasing in stability from 1 base pair to 6 base pairs with a decrease seen at 7 base pairs. The most thermodynamically stable aptamer was determined to be MN4, a preformed structure.
Open Access
An examination of facilitative interactions between shrubs and local desert organisms within the desert ecosystems of southern California
(2024-11-07) Zuliani, Mario; MacDonald, Suzanne
In recent decades, facilitative interactions have been the focus of ecological studies, specifically those with foundational shrubs within drylands. However, little has been done to analyze how the density of shrubs influence the frequency of these interactions. Here, I aim to establish shrub density as a crucial measure in ecology and facilitative interactions. I begin with a systematic review and meta-analysis (Chapter 2) to quantify the current understanding of shrub density on local animal abundance. A full text review of shrub density and animal abundance was conducted with 113 unique observations utilized in the meta-analysis. Shrub density positively predicted animal abundance, specifically within grassland and desert ecosystems. I conducted a greenhouse experiment to examine the effects of temperature on native and invasive plant species germination (Chapter 3). Temperatures were manipulated to simulate cooler microclimates and high temperature extremes. Increasing temperatures reduced germination, establishment, and biomass of all plant species, with the invasive species suffering more than natives. I conducted a telemetry experiment to determine the effects of shrub densities on an endangered species (Chapter 4). Telemetry data was combined with satellite-based counts of shrub density. Increasing shrub densities positively predicted the presence of G. sila individuals above ground. A field experiment comparing high and no shrub densities across aridity ecosystems in Southern California was conducted (Chapter 5). Camera traps were used at distinct ecosystems across southern California to determine vertebrate association. Areas of high shrub density influenced the richness and evenness of vertebrate species, while increasing temperatures negatively impacted vertebrate abundance, richness, and evenness. Finally, I tested if facilitative associations could be replicated with artificial structures (Chapter 6). Mimics were deployed within California drylands. Camera traps were utilized to estimate vertebrate communities, with temperature pendants used to contrast microclimates. Shrubs and mimics had similar microclimates, reducing the temperature underneath their canopy. Mimics displayed a higher vertebrate abundance and richness than open areas. These findings illustrate that facilitation between shrubs and dryland communities are crucial interactions. These findings suggest that shrub density is a critical measure, increasing the likelihood of interactions and possible benefits associated with shrubs.
Open Access
An Investigation into Neuroendocrine Regulators of Excretory Organs in the Adult Disease-Vector Mosquito, Aedes aegypti
(2023-08-04) Sajadi, Farwa; Paluzzi, Jean-Paul
Maintenance of ionic and osmotic homeostasis in insects allows them to succeed in many ecological and environmental niches, while utilizing a variety of feeding strategies. When faced with extreme and variable conditions, most insects regulate the composition of their blood within narrow limits. Haematophagus insects, such as the female yellow fever mosquito, Aedes aegypti, ingest bloodmeals comparable to twice their body volume, resulting in considerable amounts of salts and water in excess, threatening the osmotic and ionic balance of their haemolymph. Like other insects, mosquitoes achieve strict regulation of their hydromineral balance through the neuroendocrine control of their excretory system, consisting of the Malpighian ‘renal’ tubules (MTs), which are responsible for formation of the primary urine, along with the hindgut, which functions as a primarily reabsorptive organ. While extensive studies have examined this process of hydromineral balance in A. aegypti focusing on diuretic regulation, the roles of anti-diuretic hormones remained largely elusive. This research sought to advance our understanding of the hormonal regulation of the excretory system in A. aegypti by (1) investigating the role of CAPA neuropeptides as anti-diuretic hormones in adult MTs; (2) identifying the signalling components leading to CAPA-induced inhibition of fluid secretion; and (3) elucidating the expression and putative functional roles of ITP and ITP-L neuropeptides. In adult MTs, AedaeCAPA-1 peptides elicit a selective anti-diuretic role, inhibiting DH31- and 5HT-stimulated secretion through the NOS/cGMP/PKG pathway. CAPA-mediated inhibition promotes V-type H+-ATPase (VA) disassembly, reducing the driving force of DH31-stimulated secretion. Post-blood feeding, DH31 peptides are immediately released into the female haemolymph to promote natriuresis and diuresis while CAPA peptides are released shortly after, hindering the effects of DH31. Lastly, examination of ITP and ITP-L neuropeptides in A. aegypti indicated enrichment of ITP in the brain and ITP-L in the abdominal ganglia. Novel observations of AedaeITP and AedaeITP-L in feeding/starvation, ionoregulation, and reproductive behaviour and success suggest a vital pleiotropic role for these neuropeptides. Together, these studies highlight the complexity of neuroendocrine control of excretory organs in adult A. aegypti mosquitoes, furthering our understanding of various diuretic and anti-diuretic signalling systems in this important human disease vector.
Open Access
Analysis of Double-Crested Cormorant Nest Spatial Patterns in Single and Mixed -Species Colonies and their Effect on Cormorant Behaviour and on Black-Crowned Night Heron Spatial Patterns
(2016-09-20) Rosenberger, Lisa Charlotte; Fraser, Gail
Double-crested cormorants (Phlacrocorax auritus) are managed because they eat fish, transform habitat and can affect other waterbirds. Conversely, cormorants have been highly successful in North America since the 1970s due to increased food supply and their adaptability, although other factors may be important. I researched cormorants at Tommy Thompson Park, Ontario, and tested 1) whether tree-nesting cormorants nesting with black-crowned night herons (Nycticorax nycticorax) decreased heron population through direct or indirect effects and 2) whether ground-nesting cormorants changed their behaviours due to nest density or position and whether there was a behavioural trade-off that affected fledging success. Cormorant variables were correlated with heron declines due to indirect effects in some areas. Increased density was related to lower aggression, but there were no trade-offs between the behaviours. My research illustrates the different behaviour and spatial patterns for cormorants in single and mixed-species colonies and in ground versus tree nesting colonies.
Open Access
Analysis of Properties of Heterochromatin Relative to Meiotic Recombination and Heterochromatic Gene Expression
(2015-12-16) Taylor, Rhodri Wyndham; Hilliker, Arthur
To better understand the genetic properties of heterochromatin, I have pursued two avenues: meiotic recombination around the border of euchromatin and heterochromatin, and position effects at the heterochromatic light locus. Heterochromatin lacks recombination, and using meiotic recombination frequencies, I show that the recombination inhibition border concurs with the previously defined molecular border based on changes in histone proteins, specifically histone 3 methylation, characteristic of heterochromatin. I also show that the heterochromatic gene light behaves in a similar fashion to a previously studied heterochromatic gene, in that its function is impaired when moved out of the heterochromatic environment, but can be restored when brought near to large blocks of heterochromatin. These findings support the idea that gene function and recombination can be tightly controlled by the molecular environment of heterochromatin.
Open Access
Analysis of Spatial Learning in Honeybee Foragers Using the Food Search Box Assay
(2020-11-13) Morrison, Bandele Mojoyinola Abike; Zayed, Amro
Given the under-representation of genetic analyses of spatial learning in honeybee literature, I designed an experiment to investigate gene expression profiles associated with spatial learning. The experimental design involved using the Food Search Box (FSB) assay to assess learning in Single Drone-Inseminated (SDI) foragers, then collecting the bees for RNA-seq analysis to generate and compare full-transcriptome gene expression profiles for five different stages of learning. From the first to the third learning trial, the SDI foragers did not decrease the number of mistakes they made in a significant way: they did not switch from chance to non-chance searching behaviour. In addition, during the memory recall stage, the bees made significantly more errors than chance, suggesting they did not remember their focal flower. Landmarks cues, inter-trial interval, motivation level for sucrose and genetics may each play a role in the ability of SDI foragers to learn vs. foragers from naturally mated queens.
Open Access
Anterior Cingulate Cortex Cells Identify Errors of Attentional Control Prior to Prefrontal Disengagement
(2014-07-09) Shen, Chen; Womelsdorf, Thilo
The anterior cingulate cortex (ACC) is implicated in the detection of errors and the allocation of correctional adjustments. However, error detection alone is not sufficient to resolve and prevent future mistakes since errors can occur in various ways, subsequently requiring different adjustments. I therefore investigated whether the ACC tracks specific processing states that give rise to errors in order to identify which specific processing aspects need readjustment. To do this, my lab recorded from cells in the prefrontal cortex (PFC) of macaques while they were performing a selective-attention task that elicited three types of error. My study provides support for the functional role of the ACC in performance monitoring and specifying correctional adjustments through the tracking of specific sources of erroneous task outcomes.
Open Access
AP-1 Proteins Regulate Autophagy in Skeletal Muscle Progenitor Cells
(2019-11-22) Edwards, Tracey Anne; McDermott, John Charles
Autophagy has been observed to be a key regulator in myogenesis, maintenance of quiescence in satellite cells (SC) and regenerative capacity of skeletal muscle. Activator protein-1 (AP-1) transcription factors have been proteins of interest in autophagy regulation in various cancers due to the established roles of AP-1 in cellular proliferation, death and survival. However, AP-1 involvement in the regulation autophagy in skeletal muscle progenitor cells has not been extensively assessed. AP-1 protein c-Jun is expressed in paired box gene 7 (Pax7) positive satellite cells. AP-1 proteins c-Jun and JunB regulate autophagy. Changes to c-Jun expression lead to changed autophagosome content in C2C12 cells in both growth conditions and induced autophagy conditions. Additionally, c-Jun knockdown altered autophagosome content in cultures containing Pax7+ and Pax7- cells. AP-1 protein c-Jun appeared to be regulated by mTor. AP-1 proteins act as autophagy regulators dependent on cell type and autophagy induction method.
Open Access
Aquaporin AaAQP2 protein abundance in the anal papillae of Aedes aegypti is modified by salinity
(2021-11-15) Guardian, Elia Edith Grieco; Donini, Andrew
The Aedes aegypti mosquito, a viral disease vector, can complete its life cycle in breeding sites that range in salinity from ion-poor to fresh and brackish water. Fluctuations in salinity provide different challenges to larval regulation of ion and water transport. Western blots of proposed water channel A. aegypti aquaporin 2 (AaAQP2) revealed this protein is found in the osmoregulatory organs, including gastric caecae, Malpighian tubules (MTs), hindgut, and anal papillae (AP) of larvae reared in varying salinity. AaAQP2 immunolocalization in MTs shifted from apical to intracellular as salinity increased, and could imply AaAQP2 is trafficked from the cell membrane to potentially decrease MT water secretion. Protein abundance of the presumed AaAQP2 monomer in AP increased as salinity increased, however, larval survival increased when larvae with knockdown AaAQP2 in the AP were transferred to higher salinity. Results suggest AaAQP2 protein levels impact larval physiology when changes in environmental salinity occur.
Open Access
Aromatic Rich Natural Organic Matter Increases Growth and Reduces Nickel Toxicity in a Wild Daphnia Hybrid
(2015-08-28) Geiger, Christine Simone; Yan, Norman; Arts, Michael
Natural organic matter (NOM) is on the rise across the Shield. Its heterogeneous, amalgamate nature makes each NOM source potentially unique. Relatively little is known about the direct effects distinct NOM sources have on daphniids, or the varying protection NOM provides against metal toxicity –specifically Ni. I show that NOM from different natural sources increases growth rates and decreases time to maturation of Daphnia to various degrees. These changes relate to aromatic content of NOM isolates, the mechanism most likely being a hormonal effect or mild oxidative stress. Aromatic content (representing phenolic groups) is also positively related to Ni mitigation for those isolates with specific UV absorbance below 19.3 cm2mg-1. Incorporating NOM aromatic content into a predictive model improves the relationship between predicted and measured LC50s by 5%. I demonstrate that structural differences between NOM isolates relating to aromatic content play a major role in their effects on Daphnia.
Open Access
Assessing the Benefits of Extra-pair Mating for Female Purple Martins (Progne subis)
(2015-12-16) Kramer, Patrick Michael; Stutchbury, Bridget J.
Approximately 75% of socially monogamous passerines pursue extra-pair mating with the frequency of extra-pair paternity varying among and within taxonomic groups. Despite the ubiquity of extra-pair mating systems, substantial research into the subject has produced mixed results and the benefits to females remain elusive. Two genetic benefits hypotheses, the good genes hypothesis and heterozygosity theory, predict that extra-pair offspring (EPO) should generally be more fit than within-pair offspring (WPO). This study aims to test for genetic-based benefits to extra-pair mating in purple martins (Progne subis) by comparing EPO and WPO. Specifically, I compare the first year survival estimates of EPO and WPO and of those offspring that are recruited into the breeding population, I compare the reproductive success of EPO and WPO. I found no differences in first-year survival probability nor did I find any differences in reproductive success between EPO and WPO. I conclude that female purple martins are not benefiting from extra-pair mating through the improved survival or reproductive success of their offspring. Such benefits may be context-dependent or historical contexts in which the benefits of extra-pair mating for females may no longer exist for this semi-domesticated species.
Open Access
Assessing the Effects of Temperature, Feeding Status, and the Microbiome on the Maximal Activities of Several Enzymes Important to Energy Production and Ammonia Detoxification in the Intestines of Teleost Fish
(2020-11-13) Turner, Leah Anne; Bucking, Carol
This thesis examined the effects of temperature, feeding status, and the microbiome on the maximal activities of several enzymes important to energy production and ammonia (NH3) detoxification in the intestines of three species of teleosts: the goldfish, rainbow darter and central stoneroller. In warm-acclimated goldfish, intestinal and branchial tissues were more responsive to feeding, while renal tissues were not affected by digestion or thermal acclimation. This was reflected in the maximal enzyme activities of Na+, K+-ATPase (NKA), citrate synthase, pyruvate kinase, and glutamine synthetase (GS). Increased NKA activity following a meal suggested an increase in ATP demand, and amplified GS activity likely assists in enhanced NH3-detoxification processes in the intestinal tract. There was a strong effect of host species on intestinal tract bacteria composition and on enzyme activities in the rainbow darter and central stoneroller, and sampling location was a significant determinant of the central stoneroller intestinal microbiome.