International Conference on Sustainable Development Conference Proceedings, 2023
We explored the walking pedagogy presented on six occasions to various disciplines to ground and ... more We explored the walking pedagogy presented on six occasions to various disciplines to ground and contextualize abstract concepts surrounding the Anthropocene to enhance student learning in the broad area of sustainability. In this process, we facilitated the translation of wicked global problems of sustainability into tangible issues within a local context in order to root participants with an explicit sense of place and facilitate a potentially transformative experience. The United Nations Sustainable Development Goals (SDGs) served as a useful heuristic for critical exploration of connections between individual participants and their surrounding environment. The complexity and interconnectedness of the SDGs were discussed with participants in the context of local water quality, biodiversity, land use practices, innovation, urban renewal, and cultural issues.
Grasshopper populations from eight barrier islands off the coast of Virginia were studied over a ... more Grasshopper populations from eight barrier islands off the coast of Virginia were studied over a 25-year period. A description of the species present and their abundance and primary habitats at different times of the year is given. Nine species of grasshoppers occurred on the islands: Trimerotropis maritima, Psinidia fenestralis, Dissosteira carolina, Schistocerca alutacea, S. americana, Melanoplus differentialis, M. femurrubrum, M. bivittatus, and Arphia sulphurea. Most common were the diet specialists T. maritima and P. fenestralis, which were found on or near dunes harboring their favored host plants. Another diet specialist was S. alutacea, which occurred exclusively on wax myrtle. Melanoplus differentialis, M. femurrubrum, and M. bivittatus are generalist feeders that were common in a variety of microhabitats. Grasshopper populations could be affected by changes in host plant abundance due to significant environmental impacts. The current study can serve as a baseline for future surveys of barrier island plant and animal communities and their ecological relationships.
An investigation of the ichthyofauna inhabiting the restored mangrove wetlands of Bill Baggs Cape... more An investigation of the ichthyofauna inhabiting the restored mangrove wetlands of Bill Baggs Cape Florida State Park, Miami-Dade County, Florida, was conducted during consecutive wet and dry seasons. Twenty-eight locations were sampled using seines. Measurements of water quality, depth and benthic plant coverage were also taken. A total of 25 fish taxa were found: the most frequently occurring were the epibenthic species goldspotted killifish (Floridichthys carpio), yellow fin mojarra (Gerres cinerus) and rainwater killifish (Lucania parva). Seasonal differences in frequency of occurrence were restricted to three fishes: rainwater killifish, great barracuda (Sphyraena barracuda) and striped mullet (Mugil cephalus). Fish diversity (taxonomic richness) among the oldest mangrove habitats was significantly higher than among more recently planted habitats. Most of the fish-habitat correlations examined were weak; however, those with water temperature, depth and dissolved oxygen were significant. The presence of the subadult gray snapper (Lutjanus griseus), bluestriped grunt (Haemulon sciurus) and sailors choice (Haemulon parra) indicates that the area may be functioning in support of species with fisheries value.
A study of the rocky intertidal environments of the Florida Keys by Stephenson and Stephenson (19... more A study of the rocky intertidal environments of the Florida Keys by Stephenson and Stephenson (1950) serves as a valuable baseline of littoral communities prior to extensive development and human population pressures. Five of the study areas originally surveyed in 1947 were resurveyed in 1999 to assess any community changes which may have occurred in the intervening 52 yrs. A more extensive sampling effort in 1999 yielded a greater number of taxa as compared to 1947 (120 vs 78). However, one intertidal zone showed a decrease in taxa richness, not all species recorded in 1947 were seen in 1999, and others had shifts in abundance or zones of occurrence. The gray zone at the high mean water mark may have experienced degradation from the deposition of seagrass, debris, or hydrophobic substances as suggested by a 79% decrease in the species that occurred there, despite an increase in the number of species found in all other zones. Harvesting, pollution, or general habitat degradation may explain the complete absence or reduced abundance of some species, particularly those considered as dominant or characteristic intertidal community members in 1947. Increased nearshore eutrophication and/or changes in grazer communities may explain an apparent upward shift of some macroalgal species and the appearance at more heavily developed sites of algal nutrient indicator species (e.g., Cladophora, Chaetomorpha, and Enteromorpha). Our results are consistent with increasing evidence that disturbances, such as eutrophication, are having a negative effect on rocky intertidal communities of the Florida Keys.
The marine opistobranch mollusc, Aplysia californica J.g. Cooper, 1863, is a large herbivore that... more The marine opistobranch mollusc, Aplysia californica J.g. Cooper, 1863, is a large herbivore that inhabits the intertidal and sublittoral zones of the coast of California (Carefoot, 1987). While much work has been done on the habitat selection (pennings, 1990; 1991), feeding preferences (Carefoot, 1970) and growth (peretz and Adkins, 1982) of this animal and related species, the greatest interest in A. californica has been in its use as a model organism for neuroscience research. The relatively simple nervous system contains few neurons, yet they are large in size and easily identifiable, making it an ideal system for neurophysiologic studies. Much of what we know about learning and memory is derived from studies of A. californica (for review, see Kandel, 2001). Once the methods for rearing A. californica in the laboratory were established (Capo et al., 1987, 2002), a steady supply of animals has been available to the research community. despite this popularity as a neuroscience model, much less is known about the basic metabolic/respiratory and excretory physiology of the group. Carefoot (1988) found a strong increase in oxygen consumption during feeding, irrespective of growth, in Aplysia dactylomela Rang, 1828. Levy et al. (1989) examined the effects of hypoxia and hypercapnia on respiratory pumping of the gill in Aplysia depilans gmelin, 1791 and Aplysia fasciata poiret, 1798. Bedford and Lutz (1992) compared respiration in A. californica and Aplysia brasiliana Rang, 1828 and the effects of desiccation on oxygen uptake. however, there is a paucity of data on oxygen consumption and nitrogen metabolism in resting sea hares, which would be useful in understanding the basal metabolism of these animals and serve as a baseline for subsequent studies in growth and development. Additionally, since paradigms regarding mode of nitrogenous waste excretion in other aquatic species (especially fish, see Wright and Anderson, 2001) have been changing in recent years, and since Aplysia is an intertidal organism experiencing periods of air exposure, it seemed reasonable to expect that part of its waste may appear as urea rather than ammonia. Finally, oxygen to nitrogen ratios (O:N ratios) are an important index used in both ecological and aquacultural settings, so linked studies of oxygen consumption and nitrogen excretion in this species would provide useful information on this parameter. Therefore, the purpose of the current study was to evaluate the basal metabolism of post-metamorphic sub-adult, hatchery-reared A. californica. Specifically, we examined oxygen consumption and excretion of nitrogenous waste in a series of agematched cohorts. Since oxygen consumption can rise 2-3 fold when animals are actively feeding (Carefoot, 1988), the animals used in this study were isolated for a period of 2 d prior to measurements to allow a sufficient period of time for evacuation of the gut so that baseline (post-absorptive) measurements could be made.
Physiological and Biochemical Zoology, Sep 1, 2005
This study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve ... more This study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve as a social signal. In the first experiment, physiological parameters were measured in pairs of dominant and subordinate toadfish. Subordinate toadfish had elevated concentrations of circulating plasma cortisol, an effect maintained even after cannulation. In the second experiment, one fish of a pair was injected with 14 C-urea, and the occurrence of urea pulses during social encounters was documented. Social status did not influence the order of pulsing, that is, whether a dominant or subordinate fish pulsed first during a social encounter. However, in seven out of eight pairs, both toadfish pulsed within 2 h of each other, indicating some form of communication between fish. In the third and final experiment, the response of toadfish to urea (natural or syn-* This article is based on a presentation given in the symposium "Integration of Behaviour and Physiology," which took place at the Society for Experimental Biology annual meeting,
Physiological and Biochemical Zoology, Nov 1, 2010
Nitrogen excretion by the gulf toadfish (Opsanus beta) is of interest because of its high proport... more 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/co-incided 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.
In the present study, sagittal otoliths of confirmed male and female specimens of the gulf toadfi... more In the present study, sagittal otoliths of confirmed male and female specimens of the gulf toadfish Opsanus beta that were collected monthly over the course of a year from Biscayne Bay, Florida, U.S.A. were analysed. The timing and frequency of O. beta spawning seasons are reported by examination of the gonado-somatic index. The estimated ages of males and females ranged from <1 year to 6 and 5 years, respectively. Strong sexual dimorphism in growth was apparent with von Bertalanffy parameter estimates for males of L ∞ = 393•8 mm, K = 0•30, t 0 = 0•36 and females of L ∞ = 201•1 mm, K = 0•79, t 0 = 0•47. Comparison with previously published growth trajectories of the more northerly distributed conspecific Opsanus tau showed that O. beta males had a higher growth rate. Female O. beta and O. tau growth trajectories appear similar, with an indication that the former becomes asymptotic at least a year before the latter. Results are discussed in the context of temperature regimes, reproductive energy allocation and waste urea excretion in the two species.
Field studies were conducted in Johnson Key Basin, Florida Bay, USA from September 2002 through S... more 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 lmol N l-1 while the pH ranged from 7.48 to 9.14. There was a weak but significant correlation between environmental ammonia (NH 3) 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 lmol N l-1 and 13.0 ± 0.7 lmol N l-1 , respectively. As predicted, hepatic GS activity was significantly lower in epibenthic toadfish captured in shelters (4.40 ± 0.24 lmol min-1 g-1 ; n = 281) as compared to individuals on/in sediments (6.61 ± 0.47 lmol 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.
Silver is taken up as a Na + analog (Ag +) by freshwater organisms, but little is known about its... more 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 g L −1 silver as 110m Ag-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
The swim bladder of the oyster toadfish, Opsanus tau, has a distinctive heart shape with two ante... more The swim bladder of the oyster toadfish, Opsanus tau, has a distinctive heart shape with two anterior protrusions separated by a midline cleft. The lateral surfaces contain intrinsic muscles that meet at the caudal midline, but the rostromedial surface is muscle-free. We hypothesize that swim-bladder design represents a compromise between opposing tendencies toward (i) an omnidirectional sound source that would optimize a male's opportunity to attract females from any direction, and (ii) a directional sound source that would shield the nearby ears during sound production. To determine if the directionality of toadfish sound is consistent with this hypothesis, boatwhistle advertisement calls of individually identified males were recorded in the York River, Virginia, by means of two calibrated hydrophones and a waterproof recording system: one hydrophone was fixed 1 m in front of the fish and the second was roving. Boatwhistles in the horizontal plane propagated in a modified omnidirectional pattern that was bilaterally symmetrical. The mean sound pressure was 126 dB re: 1 µPa at 0°. The sound pressure level decreased by approximately 1 dB at ±45°, after which levels increased to 180°, averaging 3-6 dB greater behind (mean 130 dB) than directly in front of the fish. This pattern is consistent with the hypothesis that sound energy is reduced at the fish's ears. The source level and fundamental frequency of the boatwhistle were highly stereotyped, with coefficients of variation averaging less than 1%, and duration was more variable, with a coefficient of variation of 8%. Grunt levels overlapped but were slightly lower than boatwhistle values. Résumé : La vessie natatoire du crapaud de mer Opsanus tau a la forme distinctive d'un coeur et comporte deux renflements antérieurs séparés par un sillon médian. Les surfaces latérales comportent des muscles intrinsèques qui se rencontrent à la partie caudale de la ligne médiane, mais la surface rostromédiale est dépourvue de muscles. Nous posons en hypothèse que cette configuration de la vessie natatoire représente un compromis entre (i) une source sonore omnidirectionnelle qui optimise l'efficacité des mâles à attirer des femelles et (ii) une source sonore dont la nature directionnelle est propre à protéger les oreilles du poisson pendant l'émission des sons. Pour déterminer si la tendance directionnelle des sons émis confirme l'hypothèse, les signaux de type « sifflement de bateau » d'individus mâles identifiés ont été enregistrés dans la rivière York, Virginie, au moyen de deux hydrophones calibrés et d'un système d'enregistrement à l'épreuve de l'eau; un hydrophone a été placé à 1 m devant le poisson et le second suivait un mouvement de va et vient. Les signaux émis dans un plan horizontal se propageaient selon un pattern omnidirectionnel modifié à symétrie bilatérale. La pression sonore moyenne était de 126 dB re : 1µPA à 0°. Le degré de pression sonore diminuait d'environ 1 dB à ±45°, après quoi il augmentait jusqu'à 180°, en moyenne de 3-6 dB plus élevé derrière (moyenne de 130 dB) que directement devant le poisson. Cette tendance est en accord avec l'hypothèse selon laquelle l'énergie sonore est réduite au niveau des oreilles du poisson. L'intensité sonore de la source et la fréquence fondamentale des signaux étaient fortement stéréotypées, avec des coefficients de variation de moins de 1% en moyenne et, à un coefficient de variation de 8%, la durée était plus variable. Les grognements avaient des intensités qui se chevauchaient, mais légèrement plus faibles que celles des sifflements. [Traduit par la Rédaction]
The gulf toadfish (Opsanus beta) is unusual among teleosts in that it is facultatively ureotelic ... more The gulf toadfish (Opsanus beta) is unusual among teleosts in that it is facultatively ureotelic and adults and juveniles have a particularly high tolerance to environmental ammonia. Male toadfish brood their offspring in confined nests. It has been hypothesized that the potential accumulation of ammonia in nests from the male and the offspring, coupled with suspected low ammonia tolerance in offspring would provide the selective pressure necessary for excretion of the less toxic urea by adult toadfish. This study examines this so-called 'nest-fouling' hypothesis through acute and chronic ammonia toxicity testing on early life stages of O. beta. In addition, nitrogen elimination was examined among embryos, yolk-sac larvae and juveniles where we found an ontogenic shift from ammonotely to ureotely with advancing life history stages. The acute ammonia 96 h LC 50 values for embryos and larvae were 63.6 and 5.45 mmol-N l −1 total ammonia (T Amm), respectively. Thus, these early life stages are more tolerant to ammonia than either juveniles or adults and LC 50 values are at least 2 orders of magnitude greater than concentrations naturally occurring at nest sites. Furthermore, 40 days exposures at mean and maximum NH 3 concentrations normally found within nests revealed no observable detrimental effects. In fact, growth in terms of wet or dry weight was greatest at the maximum NH 3 concentration. We therefore conclude that the nest-fouling hypothesis is not a viable explanation for ureotely in the gulf toadfish.
In most teleost fishes, waste nitrogen is excreted predominantly as ammonia, with trace amounts o... more In most teleost fishes, waste nitrogen is excreted predominantly as ammonia, with trace amounts of urea produced by uricolysis or arginolysis (Wood, 1993; Walsh, 1998). While the genes regulating urea synthesis (ureogenesis) via the ornithine-urea cycle (OUC) were thought to be silenced in the more evolutionarily derived teleost fishes (Brown and Cohen, 1960), ureogenesis has been reported in embryonic and larval rainbow trout (
Glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] is an impor... more Glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] is an important enzyme of nitrogen metabolism. In the brain of all vertebrates, astrocytic GSase detoxifies ammonia during the conversion of glutamate to glutamine (at the expense of ATP), a process that is also a step in the recycling of the neurotransmitter glutamate taken up from the synaptic cleft (Cooper, 2001). In the liver of mammals, GSase has a mainly secondary or failsafe role relative to ammonia detoxification: GSase expressed in downstream perivenous hepatocytes scavenges ammonia that has not been detoxified by the ornithine-urea cycle (O-UC) expressed in the upstream periportal hepatocytes (Gebhardt and Mecke, 1983; Jungermann and Katz, 1989), where the first enzyme of urea production, carbamoyl phosphate synthetase (CPSase I) uses primarily ammonia as its nitrogen-donating substrate (for a review, see Meijer, 1995). By contrast, fish species synthesizing substantial quantities of urea de novo in an O-UC employ CPSase III, which typically prefers glutamine as nitrogen donor (for a review, see Anderson, 2002). Thus, unlike mammals, this requirement of piscine CPSase III for glutamine intimately links GSase to urea production in fish (Campbell and Anderson, 1991). In fact, in one important fish experimental system for the study of facultative urea production, the gulf toadfish Opsanus beta, GSase has emerged
University College Cork introduced its first Community-based Participatory Research (CBPR) module... more 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
Studies of prey detection by olfaction in teleost fishes have focused largely on amino acids as o... more Studies of prey detection by olfaction in teleost fishes have focused largely on amino acids as odorants, while studies with respect to nitrogenous waste are few by comparison. Although threshold sensitivities for amino acids are often in the nano-molar range, gill and renal membranes are thought to be less permeable to amino acids than lower molecular weight compounds such as ammonia or urea. Furthermore, amino acids are generally conserved for protein synthesis and are a minor constituent of excreta. This study examined detection of ammonia, urea, and amino acids by Lutjanus griseus (gray snapper ). Opsanus beta is a preferred prey item of L. griseus. O. beta is unique among teleosts in that adults can facultatively shift between ammonia and urea excretion. Experiments were conducted in 8,000 L outdoor mesocosms with flowthrough seawater and a sediment/seagrass substrate to simulate natural habitat. Odorants were injected into small experimental shelters designed to mimic toadfish...
SUMMARYWe characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [GS... more SUMMARYWe characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] in tissues of the gulf toadfish Opsanus beta subjected to unconfined(ammonotelic) and confined (ureotelic) conditions. Enzymological results demonstrate that mass-specific GSase activities rank in the order of brain> liver > stomach ≈ kidney > intestine > gill > heart/spleen> muscle. When tissue mass is used to calculate a glutamine synthetic potential, the liver has the greatest, followed by muscle > stomach and intestine, with minor contributions from the remaining tissues. Additionally,during confinement stress, GSase activity increases significantly only in liver (fivefold) and muscle (twofold), tissues that previously showed significant expression of the other enzymes of urea synthesis. Western analyses of samples on SDS gels demonstrated that GSase-specific protein content reflected enzyme activity, ...
International Conference on Sustainable Development Conference Proceedings, 2023
We explored the walking pedagogy presented on six occasions to various disciplines to ground and ... more We explored the walking pedagogy presented on six occasions to various disciplines to ground and contextualize abstract concepts surrounding the Anthropocene to enhance student learning in the broad area of sustainability. In this process, we facilitated the translation of wicked global problems of sustainability into tangible issues within a local context in order to root participants with an explicit sense of place and facilitate a potentially transformative experience. The United Nations Sustainable Development Goals (SDGs) served as a useful heuristic for critical exploration of connections between individual participants and their surrounding environment. The complexity and interconnectedness of the SDGs were discussed with participants in the context of local water quality, biodiversity, land use practices, innovation, urban renewal, and cultural issues.
Grasshopper populations from eight barrier islands off the coast of Virginia were studied over a ... more Grasshopper populations from eight barrier islands off the coast of Virginia were studied over a 25-year period. A description of the species present and their abundance and primary habitats at different times of the year is given. Nine species of grasshoppers occurred on the islands: Trimerotropis maritima, Psinidia fenestralis, Dissosteira carolina, Schistocerca alutacea, S. americana, Melanoplus differentialis, M. femurrubrum, M. bivittatus, and Arphia sulphurea. Most common were the diet specialists T. maritima and P. fenestralis, which were found on or near dunes harboring their favored host plants. Another diet specialist was S. alutacea, which occurred exclusively on wax myrtle. Melanoplus differentialis, M. femurrubrum, and M. bivittatus are generalist feeders that were common in a variety of microhabitats. Grasshopper populations could be affected by changes in host plant abundance due to significant environmental impacts. The current study can serve as a baseline for future surveys of barrier island plant and animal communities and their ecological relationships.
An investigation of the ichthyofauna inhabiting the restored mangrove wetlands of Bill Baggs Cape... more An investigation of the ichthyofauna inhabiting the restored mangrove wetlands of Bill Baggs Cape Florida State Park, Miami-Dade County, Florida, was conducted during consecutive wet and dry seasons. Twenty-eight locations were sampled using seines. Measurements of water quality, depth and benthic plant coverage were also taken. A total of 25 fish taxa were found: the most frequently occurring were the epibenthic species goldspotted killifish (Floridichthys carpio), yellow fin mojarra (Gerres cinerus) and rainwater killifish (Lucania parva). Seasonal differences in frequency of occurrence were restricted to three fishes: rainwater killifish, great barracuda (Sphyraena barracuda) and striped mullet (Mugil cephalus). Fish diversity (taxonomic richness) among the oldest mangrove habitats was significantly higher than among more recently planted habitats. Most of the fish-habitat correlations examined were weak; however, those with water temperature, depth and dissolved oxygen were significant. The presence of the subadult gray snapper (Lutjanus griseus), bluestriped grunt (Haemulon sciurus) and sailors choice (Haemulon parra) indicates that the area may be functioning in support of species with fisheries value.
A study of the rocky intertidal environments of the Florida Keys by Stephenson and Stephenson (19... more A study of the rocky intertidal environments of the Florida Keys by Stephenson and Stephenson (1950) serves as a valuable baseline of littoral communities prior to extensive development and human population pressures. Five of the study areas originally surveyed in 1947 were resurveyed in 1999 to assess any community changes which may have occurred in the intervening 52 yrs. A more extensive sampling effort in 1999 yielded a greater number of taxa as compared to 1947 (120 vs 78). However, one intertidal zone showed a decrease in taxa richness, not all species recorded in 1947 were seen in 1999, and others had shifts in abundance or zones of occurrence. The gray zone at the high mean water mark may have experienced degradation from the deposition of seagrass, debris, or hydrophobic substances as suggested by a 79% decrease in the species that occurred there, despite an increase in the number of species found in all other zones. Harvesting, pollution, or general habitat degradation may explain the complete absence or reduced abundance of some species, particularly those considered as dominant or characteristic intertidal community members in 1947. Increased nearshore eutrophication and/or changes in grazer communities may explain an apparent upward shift of some macroalgal species and the appearance at more heavily developed sites of algal nutrient indicator species (e.g., Cladophora, Chaetomorpha, and Enteromorpha). Our results are consistent with increasing evidence that disturbances, such as eutrophication, are having a negative effect on rocky intertidal communities of the Florida Keys.
The marine opistobranch mollusc, Aplysia californica J.g. Cooper, 1863, is a large herbivore that... more The marine opistobranch mollusc, Aplysia californica J.g. Cooper, 1863, is a large herbivore that inhabits the intertidal and sublittoral zones of the coast of California (Carefoot, 1987). While much work has been done on the habitat selection (pennings, 1990; 1991), feeding preferences (Carefoot, 1970) and growth (peretz and Adkins, 1982) of this animal and related species, the greatest interest in A. californica has been in its use as a model organism for neuroscience research. The relatively simple nervous system contains few neurons, yet they are large in size and easily identifiable, making it an ideal system for neurophysiologic studies. Much of what we know about learning and memory is derived from studies of A. californica (for review, see Kandel, 2001). Once the methods for rearing A. californica in the laboratory were established (Capo et al., 1987, 2002), a steady supply of animals has been available to the research community. despite this popularity as a neuroscience model, much less is known about the basic metabolic/respiratory and excretory physiology of the group. Carefoot (1988) found a strong increase in oxygen consumption during feeding, irrespective of growth, in Aplysia dactylomela Rang, 1828. Levy et al. (1989) examined the effects of hypoxia and hypercapnia on respiratory pumping of the gill in Aplysia depilans gmelin, 1791 and Aplysia fasciata poiret, 1798. Bedford and Lutz (1992) compared respiration in A. californica and Aplysia brasiliana Rang, 1828 and the effects of desiccation on oxygen uptake. however, there is a paucity of data on oxygen consumption and nitrogen metabolism in resting sea hares, which would be useful in understanding the basal metabolism of these animals and serve as a baseline for subsequent studies in growth and development. Additionally, since paradigms regarding mode of nitrogenous waste excretion in other aquatic species (especially fish, see Wright and Anderson, 2001) have been changing in recent years, and since Aplysia is an intertidal organism experiencing periods of air exposure, it seemed reasonable to expect that part of its waste may appear as urea rather than ammonia. Finally, oxygen to nitrogen ratios (O:N ratios) are an important index used in both ecological and aquacultural settings, so linked studies of oxygen consumption and nitrogen excretion in this species would provide useful information on this parameter. Therefore, the purpose of the current study was to evaluate the basal metabolism of post-metamorphic sub-adult, hatchery-reared A. californica. Specifically, we examined oxygen consumption and excretion of nitrogenous waste in a series of agematched cohorts. Since oxygen consumption can rise 2-3 fold when animals are actively feeding (Carefoot, 1988), the animals used in this study were isolated for a period of 2 d prior to measurements to allow a sufficient period of time for evacuation of the gut so that baseline (post-absorptive) measurements could be made.
Physiological and Biochemical Zoology, Sep 1, 2005
This study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve ... more This study evaluated the hypothesis that the pulsatile excretion of urea by toadfish could serve as a social signal. In the first experiment, physiological parameters were measured in pairs of dominant and subordinate toadfish. Subordinate toadfish had elevated concentrations of circulating plasma cortisol, an effect maintained even after cannulation. In the second experiment, one fish of a pair was injected with 14 C-urea, and the occurrence of urea pulses during social encounters was documented. Social status did not influence the order of pulsing, that is, whether a dominant or subordinate fish pulsed first during a social encounter. However, in seven out of eight pairs, both toadfish pulsed within 2 h of each other, indicating some form of communication between fish. In the third and final experiment, the response of toadfish to urea (natural or syn-* This article is based on a presentation given in the symposium "Integration of Behaviour and Physiology," which took place at the Society for Experimental Biology annual meeting,
Physiological and Biochemical Zoology, Nov 1, 2010
Nitrogen excretion by the gulf toadfish (Opsanus beta) is of interest because of its high proport... more 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/co-incided 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.
In the present study, sagittal otoliths of confirmed male and female specimens of the gulf toadfi... more In the present study, sagittal otoliths of confirmed male and female specimens of the gulf toadfish Opsanus beta that were collected monthly over the course of a year from Biscayne Bay, Florida, U.S.A. were analysed. The timing and frequency of O. beta spawning seasons are reported by examination of the gonado-somatic index. The estimated ages of males and females ranged from <1 year to 6 and 5 years, respectively. Strong sexual dimorphism in growth was apparent with von Bertalanffy parameter estimates for males of L ∞ = 393•8 mm, K = 0•30, t 0 = 0•36 and females of L ∞ = 201•1 mm, K = 0•79, t 0 = 0•47. Comparison with previously published growth trajectories of the more northerly distributed conspecific Opsanus tau showed that O. beta males had a higher growth rate. Female O. beta and O. tau growth trajectories appear similar, with an indication that the former becomes asymptotic at least a year before the latter. Results are discussed in the context of temperature regimes, reproductive energy allocation and waste urea excretion in the two species.
Field studies were conducted in Johnson Key Basin, Florida Bay, USA from September 2002 through S... more 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 lmol N l-1 while the pH ranged from 7.48 to 9.14. There was a weak but significant correlation between environmental ammonia (NH 3) 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 lmol N l-1 and 13.0 ± 0.7 lmol N l-1 , respectively. As predicted, hepatic GS activity was significantly lower in epibenthic toadfish captured in shelters (4.40 ± 0.24 lmol min-1 g-1 ; n = 281) as compared to individuals on/in sediments (6.61 ± 0.47 lmol 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.
Silver is taken up as a Na + analog (Ag +) by freshwater organisms, but little is known about its... more 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 g L −1 silver as 110m Ag-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
The swim bladder of the oyster toadfish, Opsanus tau, has a distinctive heart shape with two ante... more The swim bladder of the oyster toadfish, Opsanus tau, has a distinctive heart shape with two anterior protrusions separated by a midline cleft. The lateral surfaces contain intrinsic muscles that meet at the caudal midline, but the rostromedial surface is muscle-free. We hypothesize that swim-bladder design represents a compromise between opposing tendencies toward (i) an omnidirectional sound source that would optimize a male's opportunity to attract females from any direction, and (ii) a directional sound source that would shield the nearby ears during sound production. To determine if the directionality of toadfish sound is consistent with this hypothesis, boatwhistle advertisement calls of individually identified males were recorded in the York River, Virginia, by means of two calibrated hydrophones and a waterproof recording system: one hydrophone was fixed 1 m in front of the fish and the second was roving. Boatwhistles in the horizontal plane propagated in a modified omnidirectional pattern that was bilaterally symmetrical. The mean sound pressure was 126 dB re: 1 µPa at 0°. The sound pressure level decreased by approximately 1 dB at ±45°, after which levels increased to 180°, averaging 3-6 dB greater behind (mean 130 dB) than directly in front of the fish. This pattern is consistent with the hypothesis that sound energy is reduced at the fish's ears. The source level and fundamental frequency of the boatwhistle were highly stereotyped, with coefficients of variation averaging less than 1%, and duration was more variable, with a coefficient of variation of 8%. Grunt levels overlapped but were slightly lower than boatwhistle values. Résumé : La vessie natatoire du crapaud de mer Opsanus tau a la forme distinctive d'un coeur et comporte deux renflements antérieurs séparés par un sillon médian. Les surfaces latérales comportent des muscles intrinsèques qui se rencontrent à la partie caudale de la ligne médiane, mais la surface rostromédiale est dépourvue de muscles. Nous posons en hypothèse que cette configuration de la vessie natatoire représente un compromis entre (i) une source sonore omnidirectionnelle qui optimise l'efficacité des mâles à attirer des femelles et (ii) une source sonore dont la nature directionnelle est propre à protéger les oreilles du poisson pendant l'émission des sons. Pour déterminer si la tendance directionnelle des sons émis confirme l'hypothèse, les signaux de type « sifflement de bateau » d'individus mâles identifiés ont été enregistrés dans la rivière York, Virginie, au moyen de deux hydrophones calibrés et d'un système d'enregistrement à l'épreuve de l'eau; un hydrophone a été placé à 1 m devant le poisson et le second suivait un mouvement de va et vient. Les signaux émis dans un plan horizontal se propageaient selon un pattern omnidirectionnel modifié à symétrie bilatérale. La pression sonore moyenne était de 126 dB re : 1µPA à 0°. Le degré de pression sonore diminuait d'environ 1 dB à ±45°, après quoi il augmentait jusqu'à 180°, en moyenne de 3-6 dB plus élevé derrière (moyenne de 130 dB) que directement devant le poisson. Cette tendance est en accord avec l'hypothèse selon laquelle l'énergie sonore est réduite au niveau des oreilles du poisson. L'intensité sonore de la source et la fréquence fondamentale des signaux étaient fortement stéréotypées, avec des coefficients de variation de moins de 1% en moyenne et, à un coefficient de variation de 8%, la durée était plus variable. Les grognements avaient des intensités qui se chevauchaient, mais légèrement plus faibles que celles des sifflements. [Traduit par la Rédaction]
The gulf toadfish (Opsanus beta) is unusual among teleosts in that it is facultatively ureotelic ... more The gulf toadfish (Opsanus beta) is unusual among teleosts in that it is facultatively ureotelic and adults and juveniles have a particularly high tolerance to environmental ammonia. Male toadfish brood their offspring in confined nests. It has been hypothesized that the potential accumulation of ammonia in nests from the male and the offspring, coupled with suspected low ammonia tolerance in offspring would provide the selective pressure necessary for excretion of the less toxic urea by adult toadfish. This study examines this so-called 'nest-fouling' hypothesis through acute and chronic ammonia toxicity testing on early life stages of O. beta. In addition, nitrogen elimination was examined among embryos, yolk-sac larvae and juveniles where we found an ontogenic shift from ammonotely to ureotely with advancing life history stages. The acute ammonia 96 h LC 50 values for embryos and larvae were 63.6 and 5.45 mmol-N l −1 total ammonia (T Amm), respectively. Thus, these early life stages are more tolerant to ammonia than either juveniles or adults and LC 50 values are at least 2 orders of magnitude greater than concentrations naturally occurring at nest sites. Furthermore, 40 days exposures at mean and maximum NH 3 concentrations normally found within nests revealed no observable detrimental effects. In fact, growth in terms of wet or dry weight was greatest at the maximum NH 3 concentration. We therefore conclude that the nest-fouling hypothesis is not a viable explanation for ureotely in the gulf toadfish.
In most teleost fishes, waste nitrogen is excreted predominantly as ammonia, with trace amounts o... more In most teleost fishes, waste nitrogen is excreted predominantly as ammonia, with trace amounts of urea produced by uricolysis or arginolysis (Wood, 1993; Walsh, 1998). While the genes regulating urea synthesis (ureogenesis) via the ornithine-urea cycle (OUC) were thought to be silenced in the more evolutionarily derived teleost fishes (Brown and Cohen, 1960), ureogenesis has been reported in embryonic and larval rainbow trout (
Glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] is an impor... more Glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] is an important enzyme of nitrogen metabolism. In the brain of all vertebrates, astrocytic GSase detoxifies ammonia during the conversion of glutamate to glutamine (at the expense of ATP), a process that is also a step in the recycling of the neurotransmitter glutamate taken up from the synaptic cleft (Cooper, 2001). In the liver of mammals, GSase has a mainly secondary or failsafe role relative to ammonia detoxification: GSase expressed in downstream perivenous hepatocytes scavenges ammonia that has not been detoxified by the ornithine-urea cycle (O-UC) expressed in the upstream periportal hepatocytes (Gebhardt and Mecke, 1983; Jungermann and Katz, 1989), where the first enzyme of urea production, carbamoyl phosphate synthetase (CPSase I) uses primarily ammonia as its nitrogen-donating substrate (for a review, see Meijer, 1995). By contrast, fish species synthesizing substantial quantities of urea de novo in an O-UC employ CPSase III, which typically prefers glutamine as nitrogen donor (for a review, see Anderson, 2002). Thus, unlike mammals, this requirement of piscine CPSase III for glutamine intimately links GSase to urea production in fish (Campbell and Anderson, 1991). In fact, in one important fish experimental system for the study of facultative urea production, the gulf toadfish Opsanus beta, GSase has emerged
University College Cork introduced its first Community-based Participatory Research (CBPR) module... more 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
Studies of prey detection by olfaction in teleost fishes have focused largely on amino acids as o... more Studies of prey detection by olfaction in teleost fishes have focused largely on amino acids as odorants, while studies with respect to nitrogenous waste are few by comparison. Although threshold sensitivities for amino acids are often in the nano-molar range, gill and renal membranes are thought to be less permeable to amino acids than lower molecular weight compounds such as ammonia or urea. Furthermore, amino acids are generally conserved for protein synthesis and are a minor constituent of excreta. This study examined detection of ammonia, urea, and amino acids by Lutjanus griseus (gray snapper ). Opsanus beta is a preferred prey item of L. griseus. O. beta is unique among teleosts in that adults can facultatively shift between ammonia and urea excretion. Experiments were conducted in 8,000 L outdoor mesocosms with flowthrough seawater and a sediment/seagrass substrate to simulate natural habitat. Odorants were injected into small experimental shelters designed to mimic toadfish...
SUMMARYWe characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [GS... more SUMMARYWe characterized the expression of the nitrogen metabolism enzyme glutamine synthetase [GSase; L-glutamate: ammonia ligase (ADP-forming), E.C. 6.3.1.2] in tissues of the gulf toadfish Opsanus beta subjected to unconfined(ammonotelic) and confined (ureotelic) conditions. Enzymological results demonstrate that mass-specific GSase activities rank in the order of brain> liver > stomach ≈ kidney > intestine > gill > heart/spleen> muscle. When tissue mass is used to calculate a glutamine synthetic potential, the liver has the greatest, followed by muscle > stomach and intestine, with minor contributions from the remaining tissues. Additionally,during confinement stress, GSase activity increases significantly only in liver (fivefold) and muscle (twofold), tissues that previously showed significant expression of the other enzymes of urea synthesis. Western analyses of samples on SDS gels demonstrated that GSase-specific protein content reflected enzyme activity, ...
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