A Transferable Infochemical for Multiple Crustaceans and Mechanistic Assessment of its pH Dependency

Many organisms rely on their sense of smell to explore and interact with their environment. Meeting another organism, infochemicals help them decide whether to eat it, flee, fight or mate with it. The infochemical 2-phenylethylamine (PEA) has previously been associated with predator avoidance in mammals and feeding deterrence in algae. This thesis explores the hypothesis that PEA also induces a comparable avoidance behaviour in crustaceans. In behaviour assays with shore crabs and hermit crabs, movement patterns and behavioural displays were explored in current average marine pH conditions and end-of-the-century average pH, as associated with climate change. Furthermore, using liquid chromatography with tandem mass-spectrometry, shore crab urine was analysed for PEA. Results indicate that PEA attracts both species in reduced pH conditions, rather than deterring them as expected for a predator cue. Agonistic displays in response to PEA and evidence for PEA in shore crab urine suggest that PEA mediates agonistic interactions in crustaceans. Excreted with urine, PEA elicits the full behavioural response in crustaceans only in decreased pH conditions. Therefore, this thesis tested the hypothesis that the pH-dependent response hinges on pH-dependent changes to the infochemical itself. Quantum chemical computations validated by nuclear magnetic resonance (NMR) spectroscopy allowed calculating PEA's different protonation states, and its interaction with a model receptor in different protonation states. Results confirm that the pH-dependent response to PEA could be attributed to changes in charge distribution in the infochemical, potentially leading to altered receptor-ligand affinity. A comparison with the neurotransmitter dopamine reveals that the exact chemical structure and charge distribution of PEA matters for its biological function. Although dopamine and PEA are broadly chemically similar, their biological role for crustaceans appears different. In summary, PEA is an infochemical mediating agonistic interactions in crustaceans in a pH-dependent manner

Ocean Acidification Amplifies the Olfactory Response to 2-Phenylethylamine: Altered Cue Reception as a Mechanistic Pathway?

With carbon dioxide (CO2) levels rising dramatically, climate change threatens marine environments. Due to increasing CO2 concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. Living in intertidal environments, hermit crabs face large pH fluctuations in their current habitat in addition to climate-change related ocean acidification. We demonstrate that the dietary predator cue PEA for mammals and sea lampreys is an attractant for hermit crabs, with the potency of the cue increasing with decreasing pH levels. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH-dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems

Catchment-wide interactive effects of anthropogenic structures and river levels on fish spawning migrations

Worldwide, rivers are extensively fragmented by anthropogenic structures, reducing longitudinal connectivity, inhibiting migration and leading to severe declines in many fish populations, especially for diadromous species. However, few studies have determined the effects of annual differences in hydrology on catchment penetration past barriers to spawning habitats. We investigated the upstream spawning migration of 120 (n = 61 & 59) acoustic tagged river lamprey (Lampetra fluviatilis) across two contrasting (dry and wet) years in the River Yorkshire Ouse, England. Overall, significantly more lamprey reached spawning habitat (76% vs 39%) and penetrated significantly further upstream (median [km] from release, 53.9 vs 16.8) in the wet year than the dry year. Passage at weirs was almost exclusively during elevated river levels, which directly and collectively influenced catchment-wide distribution, especially in the dry year. Indeed, higher proportions entered two upper tributaries in the wet year (9.8% vs 27.1% and 9.8% vs 30.5%), due to increased passage efficiencies at the two main river weirs (60.5–87.5% and 54.5–83.8%), and reached assumed spawning locations 66.5% and 10.9% quicker. By contrast, there was no difference in numbers of lamprey entering, or time taken to arrive at assumed spawning location, in the two lower river tributaries between years. Our study supports the landscape-scale paradigm for ecosystem restoration because of the observed catchment-level effects of hydrology and barrier distribution on fish migration. Connectivity restoration for migratory fish should be implemented at a catchment scale, with planning incorporating spatial information regarding accessibility to key habitats to reap the largest gains

Respirometer experiments recording oxygen consumption and a behavioural choice bioassay of the hermit crab Pagurus bernhardus to the plastic additive oleamide

The physiological and behavioural responses of the hermit crab Pagurus bernhardus to the plastic additive oleamide was assessed. This was evaluated via respirometer experiments that recorded oxygen consumption, and a behavioural choice bioassay. In February 2019, 40 hermit crabs were collected from the rocky intertidal shore near Scarborough (54°25'19.6”N 0°31'43.6”W), North Yorkshire, UK, and then transported to the aquarium facilities at the University of Hull. Hermit crabs were housed in individual containers in three 200 L tanks as part of a recirculation system (1600 L) filled with artificial seawater and acclimatised to a twice weekly feeding rhythm with cooked blue mussels. A 12 h/ 12 h light/dark cycle period was in place to simulate day/night rhythms. Hermit crabs were kept at pH 8.1±0.1, an average temperature of 15.8±0.2°C and 35.9± 0.2 PSU. All collections and experiments were conducted following national and/or institutional guidelines. Approval was granted by the Ethics Committee of the University of Hull (No. UO20, FEC_2019_155). Experimental trials were conducted in March 2019 – April 2019. Dissolved oxygen saturation was recorded inside the respirometer chamber at the start and end of two-minute intervals (before and after the injection of the cue). The difference between the oxygen concentrations at the start and the end of the interval showed the oxygen consumption for the time period. For the statistical analysis, the computing software R (version 3.5.2; R Core Team. (2018). R: a language and environment of statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/) was used. The distribution of data proved to be not normal (Shapiro-Wilk test, p=0.02), so non-parametric paired Wilcoxon tests were used to determine whether the differences in oxygen consumption were significantly different before and after injection and between test and control conditions. P-values were adjusted using the Bonferroni correction method. To analyse the difference between time spent in each of the test conditions, the statistical software R (R Core Team. (2018). R: a language and environment of statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/) was used. The distribution of the data was firstly checked via the Shapiro-Wilk test and inspected using histograms and quantile-quantile (QQ) plots. All Shapiro-Wilk tests cross referenced with histograms and QQ plots confirmed that the data was not normally distributed. Hence, the data was analyzed using the non-parametric Friedman rank sum test. Where the Friedman test indicated a significant difference, the Nemenyi post-hoc test was then used for multiple comparisons. Hermit crabs that stayed in their shell for the entire duration of the seawater control or solvent control assay were deemed inactive and excluded from the dataset. Treatment and testing order were randomized for both experiments, as was the side of test and control zones for bioassay experiments. Each hermit crab was only tested on one cue per day of experimentation, with an interval of 24 hours between trials to minimize stress and likelihood of a decreased response to cues over time

York Open Research: Summer 2020 awareness and engagement survey

Report from a survey to assess current levels of awareness and engagement and to identify the main barriers to open research practice at the University of York

University of York Open Research Team

A repository for reports, training materials and other resources created by the University of York Open Research tea

Becoming nose-blind—Climate change impacts on chemical communication

Chemical communication via infochemicals plays a pivotal role in ecological interactions, allowing organisms to sense their environment, locate predators, food, habitats, or mates. A growing number of studies suggest that climate change-associated stressors can modify these chemically mediated interactions, causing info-disruption that scales up to the ecosystem level. However, our understanding of the underlying mechanisms is scarce. Evidenced by a range of examples, we illustrate in this opinion piece that climate change affects different realms in similar patterns, from molecular to ecosystem-wide levels. We assess the importance of different stressors for terrestrial, freshwater, and marine ecosystems and propose a systematic approach to address highlighted knowledge gaps and cross-disciplinary research avenues

Novel Aspects of Renal Magnesium Homeostasis

Magnesium (Mg2+) is indispensable for several vital functions, such as neurotransmission, cardiac conductance, blood glucose, blood pressure regulation, and proper function of more than 300 enzymes. Thus, Mg2+ homeostasis is subject to tight regulation. Besides the fast and immediate regulation of plasma Mg2+, a major part of Mg2+ homeostasis is realized by a concerted action of epithelial molecular structures that tightly control intestinal uptake and renal absorption. This mechanism is provided by a combination of para- and transcellular pathways. Whereas the first pathway provides the organism with a maximal amount of vital substances by a minimal energy expenditure, the latter enables controlling and fine-tuning by means of local and regional regulatory systems and also, hormonal control. The paracellular pathway is driven by an electrochemical gradient and realized in principal by the tight junction (TJ), a supramolecular organization of membrane-bound proteins and their adaptor and scaffolding proteins. TJ determinants are claudins (CLDN), a family of membrane spanning proteins that generate a barrier or a pore between two adjacent epithelial cells. Many insights into molecular mechanisms of Mg2+ handling have been achieved by the identification of alterations and mutations in human genes which cause disorders of paracellular Mg2+ pathways (CLDN10, CLDN14, CLDN16, CLDN19). Also, in the distal convoluted tubule, a basolateral protein, CNNM2, causes if mutated, familial dominant and also recessive renal Mg2+ wasting, albeit its true function has not been clarified yet, but is assumed to play a key role in the transcellular pathway. Moreover, mutations in human genes that are involved in regulating these proteins directly or indirectly cause, if mutated human diseases, mostly in combination with comorbidities as diabetes, cystic renal disease, or metabolic abnormalities. Generation and characterization of animal models harboring the corresponding mutations have further contributed to the elucidation of physiology and pathophysiology of Mg2+ disorders. Finally, high-end crystallization techniques allow understanding of Mg2+ handling in more detail. As this field is rapidly growing, we describe here the principles of physiology and pathophysiology of epithelial transport of renal Mg2+ homeostasis with emphasis on recently identified mechanisms involved