Community research report

University College Cork introduced its first Community-based Participatory Research (CBPR) module in 2016. The module was funded and supported by Horizon2020 funding, specifically the EnRRICH project (Enhancing Responsible Research and Innovation through Curricula in Higher Education). The module is a 5-credit module for PhD students from all disciplines in the early stages of their PhD at University College Cork. Following two fruitful partnerships in the areas of social justice / equality, community family support services and older persons, there was a keen interested to explore partnerships in markedly different areas such as environmental sustainability. A dialogue ensued with CEF where the opportunity and feasibility to collaborate on the CBPR module was explored

The adaptive significance of ureotelism in the gulf toadfish, Opsanus beta

The gulf toadfish Opsanus beta (Batrachoididae) is one of the few teleosts that maintains a functional ornithine-urea cycle during adult life and possesses the capability of facultatively shifting from ammonotely to ureotely within 24 h under laboratory conditions. Three hypotheses were examined with respect to the adaptive significance of ureotely in O. beta: environmental loading of ammonia, nest maintenance and chemical crypsis.Ureotely was first studied in response to micro-habitat variations in environmental ammonia and other environmental variables using glutamine synthetase (GSase) activity as a proxy for ureogenesis in order to examine the ammonia loading hypothesis. Extremely weak, but significant correlations emerged between environmental ammonia (NH3) concentrations and hepatic GSase activity from both burrowing toadfish (p = 0.005, r2 value = 0.073) and nesting toadfish (p \u3c 0.001, r2 value = 0.076). Mean urea and TAmm concentrations found in shelters occupied by toadfish (n = 281) were 9.8 +/- 0.83 and 13.0 +/- 0.7 mumol-N·l -1, respectively.The mechanism of ureogenesis and patterns of urea excretion across early-life history stages of O. beta were investigated to examine the nest-fouling hypothesis. Juveniles were the most sensitive developmental stage with an TAmm 96-h LC50 value was 875 mumol-N·l -1 which was over an order of magnitude above values found within nests. Furthermore, 40 d exposures at mean and maximum NH3 concentrations occurring within nests revealed no observable detrimental effects and, in fact, growth in terms of wet or dry weight was greatest in the 300 mumol-N·l -1 TAmm treatment.Chemoreception experiments with the toadfish predator Lutjanus griseus were performed to determine behavioral responses toward ammonia and urea in an examination of the chemical crypsis hypothesis. Our results indicate that L. griseus was more responsive to ammonia than either urea or an ammonia/urea mix with threshold sensitivities \u3c5 mumol-N·l -1. Additionally, L. griseus was more responsive to an amino acid-ammonia mix than either an amino acid-urea mix or amino acids without waste-N. These results suggest urea masks or camouflages ammonia odors, but not those of amino acids. Thus, chemical crypsis may confer a selective advantage to ureotelic toadfish because they are less likely to be chemically detected by teleost predators

Habitat use, urea production and spawning in the gulf toadfish Opsanus beta

Field studies were conducted in Johnson Key Basin, Florida Bay, USA from September 2002 through September 2004 to examine physiological, ecological, and behavioral characteristics of the gulf toadfish, Opsanus beta (Goode and Bean in Proc US Natl Mes 3:333–345, 1880), in relation to nitrogen metabolism, habitat usage, and spawning. Fish collected 5 cm above sediments in experimental shelters (epibenthic) were compared with those collected by throw traps which were found on or burrowing within sediments. The relationship between microhabitat ammonia and urea excretion, as determined by the enzymatic activity of glutamine synthetase (GS), was examined. The hypothesis tested was that O. beta occupying epibenthic nests were less ureotelic with lower GS activities than non-nesting individuals on/in sediments, due to a decreased environmental ammonia burden. Porewater total ammonia (T Amm) concentrations at a sediment depth of 5 cm, i.e., the approximate depth of burrowing toadfish, ranged from 0 to 106.5 μmol N l−1 while the pH ranged from 7.48 to 9.14. There was a weak but significant correlation between environmental ammonia (NH3) concentration and hepatic GS activity for epibenthic toadfish (P < 0.001, r 2 = 0.10), but not for burrowing toadfish. Mean urea-N and T Amm concentrations within shelters occupied by toadfish (n = 281) were 9.8 ± 0.83 μmol N l−1 and 13.0 ± 0.7 μmol N l−1, respectively. As predicted, hepatic GS activity was significantly lower in epibenthic toadfish captured in shelters (4.40 ± 0.24 μmol min−1 g−1; n = 281) as compared to individuals on/in sediments (6.61 ± 0.47 μmol min−1 g−1; n = 128). Glutamine synthetase activity generally peaked in March (spawning season) and was lowest in July. Gender differences in hepatic and branchial GS activity were also found during the spawning season, which is attributable to the fact that males brood and guard offspring in their epibenthic nests while females often rest on or burrow into the sediments. Finally, hepatic and branchial GS appeared to have different patterns of enzymatic activity suggesting functional differences in gene expression

Diel patterns of nitrogen excretion, plasma constituents, and behavior in the gulf toadfish (Opsanus beta) in laboratory versus outdoor mesocosm settings

Nitrogen excretion by the gulf toadfish (Opsanus beta) is of interest because of its high proportion of urea excretion compared with that of other teleosts. To better understand the factors influencing the timing of nitrogen excretion, the ratio of excreted urea∶ammonia, and the effector molecules regulating these processes, gulf toadfish were subjected to a series of experiments that moved them progressively from internal laboratory to outdoor mesocosm settings while assessing their behavior, nitrogen excretion patterns, levels of plasma hormones/effectors, and other parameters. In confined flux chambers in both laboratory and outdoor settings, toadfish nitrogen excretion was largely observed as urea pulses, with no apparent diel patterns to the pulses. Unrestrained toadfish in mesocosms exhibited distinctly nocturnal behavior, remaining exclusively in shelters during the day but taking several forays out into the mesocosm at night. In contrast to nitrogen excretion patterns in chambers, urea and ammonia were coexcreted in mesocosms and ratios for urea∶ammonia were very close to 1∶1 for both fed and fasted toadfish. The majority of measured excretion (and corresponding declines in plasma urea levels) occurred during two distinct periods of pulsing during daylight hours (0600-1000 and 1600-1800 hours). The declines in plasma urea associated with excretion were preceded by/coincided with declines in plasma cortisol. No day/night or hourly patterns in plasma serotonin (5-hydroxytryptamine [5-HT]) were observed, but there was a strong positive correlation among all samples between plasma urea and 5-HT. There was also a negative correlation between plasma cortisol and 5-HT. As expected for a nocturnally active species, plasma melatonin was significantly lower in daylight hours. A variety of enzyme activities (glutamine synthetase, glutaminase) and mRNA levels (glutamine synthetase, urea transporter, and Rhesus proteins) showed no significant variation over a diel cycle. Unlike prior laboratory studies, our results show that gulf toadfish in a natural setting have a distinctly diurnal pattern of nitrogen excretion and that ammonia and urea are coexcreted. The decline in plasma cortisol associated with urea pulses noted in prior laboratory studies was not as evident in the natural setting

Is urea pulsing in toadfish related to environmental O2 or CO2 levels?

The neurochemical, serotonin (5-hydroxytryptamine; 5-HT) is involved in the regulation of toadfish pulsatile urea excretion as well as the teleost hypoxia response. Thus, the goal of this study was to determine whether environmental conditions that activate branchial chemoreceptors also trigger pulsatile urea excretion in toadfish, since environmental dissolved oxygen levels in a typical toadfish habitat show significant diel fluctuations, often reaching hypoxic conditions at dawn. Toadfish were fitted with arterial, venous and/or buccal catheters and were exposed to various environmental conditions, and/or injected with the O(2) chemoreceptor agonist NaCN or the 5-HT(2) receptor agonist alpha-methyl-5HT. Arterial PO(2), as well as ammonia and urea excretion were monitored. Natural fluctuations in arterial PO(2) levels in toadfish did not correlate with the occurrence of a urea pulse. Chronic exposure (24 h) of toadfish to hyperoxia was without effect on nitrogen excretion, however, exposure to hypoxia caused a significant reduction in the frequency of urea pulses, and exposure to hypercapnia resulted in a reduction in the percentage of nitrogen waste excreted as urea. Of toadfish exposed acutely to hypoxia, 20% pulsed within 1 h, whereas none pulsed after normoxic or hypercapnic treatments. Furthermore, 20% of fish injected intravenously with NaCN pulsed within 1 h of injection, but no fish pulsed after injection of NaCN into the buccal cavity. To test whether environmental conditions affected 5-HT(2) receptors, toadfish were injected with alpha-methyl-5HT, which elicits urea pulses in toadfish. No significant differences in pulse size occurred among the various environmental treatments. Our findings suggest that neither the environmental conditions of hypoxia, hyperoxia or hypercapnia, nor direct branchial chemoreceptor activation by NaCN play a major role in the regulation of pulsatile urea excretion in toadfish

Bioavailability of silver and its relationship to ionoregulation and silver speciation across a range of salinities in the gulf toadfish ( Opsanus beta)

Silver is taken up as a Na + analog (Ag +) by freshwater organisms, but little is known about its bioavailability in relation to salinity. Adult Opsanus beta were acclimated to 2.5, 5, 10, 20, 40, 60, 80, and 100% seawater (Cl − = 545 mM) and exposed for 24 h to 2.18 μg L −1 silver as 110mAg-labelled AgNO 3, a concentration close to the U.S. EPA marine criterion and less than 0.1% of the acute 96-h LC50 in seawater. Plasma osmolality, Na +, and Cl − remained approximately constant from 100% down to 20–40% seawater, thereafter declining to 89% (osmolality) and 82% (Na +, Cl −) of seawater values at the lowest salinity (2.5% seawater), while plasma Mg 2+ was invariant. Ionic measurements in intestinal fluids and urine supported the view that above the isosmotic point (about 32% seawater), toadfish drink the medium, absorb Na +, Cl −, and water across the gastrointestinal tract, actively excrete Na + and Cl − across the gills, and secrete Mg 2+ into the urine. Below this point, toadfish appear to stop drinking, actively take up Na + and Cl − at the gills, and retain ions at the kidney. Silver accumulation varied greatly with salinity, by nine-fold (whole body), 26-fold (gill tissue), and 18-fold (liver), with the maxima occurring in 2.5% seawater, the minima in 40% seawater (close to the isosmotic point), and slightly greater values at higher salinities. Highest silver concentrations occurred in liver, second highest in gills, intermediate concentrations in kidney, spleen, and gastrointestinal tissues, and lowest in swim bladder and white muscle, though patterns changed with salinity. There were substantial biliary but minimal urinary levels of silver. The salinity-dependent pattern of silver accumulation best correlated with the abundance of the neutral complex AgCl 0, though the presence of small amounts of Ag + at the lowest salinities may also have been important. In contrast, silver accumulation in the esophagus-stomach was greatest in 100% seawater and least at the isosmotic salinity (five-fold variation), a pattern probably explained by drinking and silver uptake into the blood through the gills. Models of silver bioavailability across salinity must consider the presence of silver-binding ligands on both gills and gastrointestinal tract, changing silver speciation, and the changing ionoregulatory physiology of the organism

Community research report

University College Cork introduced its first Community-based Participatory Research (CBPR) module in 2016. The module was funded and supported by Horizon2020 funding, specifically the EnRRICH project (Enhancing Responsible Research and Innovation through Curricula in Higher Education). The module is a 5-credit module for PhD students from all disciplines in the early stages of their PhD at University College Cork. Following two fruitful partnerships in the areas of social justice / equality, community family support services and older persons, there was a keen interested to explore partnerships in markedly different areas such as environmental sustainability. A dialogue ensued with CEF where the opportunity and feasibility to collaborate on the CBPR module was explored