Distribution of FMRFamide-like immunoreactivity in the brain of the elasmobranch fish Scyliorhinus canicula.

The distribution of FMRFamide-like-immunoreactive peptides was investigated in the brain and pituitary of the elasmobranch fish Scyliorhinus canicula using the indirect immunofluorescence technique. FMRFamide-immunoreactive cells and fibers were mainly observed in the telencephalon and the diencephalon, while other brain structures were almost unstained. In the telencephalon, FMRFamide-like-containing neurons were seen in the caudal part of the area periventricularis pallialis, in the posterior area of the nucleus septi medialis and in the nucleus septi caudoventralis. In the diencephalon, numerous FMRFamide-positive cell bodies were observed in the hypothalamus, ventral thalamus and posterior tuberculum. The highest density of immunofluorescent perikarya was found in the nucleus lobi lateralis hypothalami and in the nucleus periventricularis hypothalami. More caudally, the mesencephalon and the caudal brainstem only contained scattered varicose FMRFamide-immunoreactive fibers. Stained fibers were also identified in the median eminence and several FMRFamide-like-positive cells were detected in the dorsal and rostral parts of the neurointermediate lobe of the pituitary. These data indicate that substances related to the molluscan cardioexcitatory peptide FMRFamide are widely distributed in the brain of S. canicula, suggesting their implication in neuroendocrine and/or neuromodulatory functions.     

Localization of corticotropin-releasing hormone (CRF)-like immunoreactivity in the central nervous system of the elasmobranch fish,Scyliorhinus canicula

Summary The occurrence and localization of immunoreactive corticotropin-releasing factor (CRF) in the brain and pituitary of the elasmobranch fish Scyliorhinus canicula, were studied by means of specific radioimmunoassay and immunohistochemistry using the indirect immunofluorescence method. Brain and pituitary extracts showed a good cross-reactivity with the ovine CRF antiserum, but serial dilutions of tissue samples did not completely parallel the standard curve. Relatively high concentrations of CRF-like material were found within the pituitary, diencephalon, and telencephalon. CRF-like immunoreactive perikarya were observed in the preoptic nucleus and in the nucleus lateralis tuberis. Numerous immunoreactive cells appeared to be of the CSF-contacting type. CRF-like immunopositive fibers were seen to run through the hypothalamus within the ventro-medial floor of the infundibular region. A dense plexus of immunoreactive nerve endings terminated in the median eminence and the neurointermediate lobe of the pituitary. These results indicate that a neurosecretory system containing CRF-like immunoreactivity exists in the brain of elasmobranchs, a group of vertebrates which has diverged early from the evolutionary line leading to mammals. In addition, our data support the notion that a CRF-like molecule is involved in the regulation of corticotropic and melanotropic cell activity in this primitive species of fish.     

Localization of atrial natriuretic factor (ANF)-related peptides in the central nervous system of the elasmobranch fish Scyliorhinus canicula

We have investigated the localization of atrial natriuretic factor (ANF)-like immunoreactivity in the central nervous system of the cartilaginous fish, Scyliorhinus canicula, using the indirect immunofluorescence technique. Immunoreactive perikarya and fibers were observed in two regions of the telencephalon, the area superficialis basalis and the area periventricularis ventrolateralis. In the diencephalon, the hypothalamus exhibited a moderate number of ANF-containing neurons and fibers located in the preoptic and periventricular nuclei and in the nucleus lateralis tuberis. The most important group of ANF-immunoreactive cells was observed in the nucleus tuberculi posterioris of the diencephalon. In contrast, the mesencephalon showed only a few ANF-positive nerve processes located in the tegmentum mesencephali. Numerous fine fibers and nerve terminals were found in the dorsal area of the neurointermediate lobe of the pituitary. These results provide the first evidence for the presence of ANF-related peptides in the brain of a cartilaginous fish. The widespread distribution of ANF-positive cells and fibers in the brain and pituitary suggests that this peptide may act both as a neurotransmitter and (or) a neurohormone in fish.     

Occurrence of bombesin-like immunoreactivity in the brain of the cartilaginous fish,Scyliorhinus canicula

Summary The presence and distribution of bombesin-like material were investigated in the brain of the cartilaginous fishScyliorhinus canicula using conventional immunocytochemical techniques. Perikarya containing bombesin-like immunoreactivity were identified in the hypothalamus, within the magnocellular component of the preoptic nucleus. Some immunopositive elements appeared to be of cerebrospinal fluid-contacting type. Beaded immunoreactive fibers were seen crossing the ventral telencephalon and the whole hypothalamus. An important tract of fibers was found in the infundibular floor and in the median eminence, in close contact with the vascular system of the pituitary portal plexus. A moderate number of positive fibers innervated the habenular complex and the dorsal wall of the posterior tuberculum. These findings indicate that a neuropeptide strictly related to amphibian bombesin is located in specific hypothalamic neurons ofS. canicula. The distribution of the immunoreactive fibers and terminals suggests that, in fish, this peptide, may be involved in neuroendocrine and neuromodulator functions.     

Two decades of genetic profiling yields first evidence of natal philopatry and long‐term fidelity to parturition sites in sharks

Sharks are a globally threatened group of marine fishes that often breed in their natal region of origin. There has even been speculation that female sharks return to their exact birthplace to breed (‘natal philopatry’), which would have important conservation implications. Genetic profiling of lemon sharks (Negaprion brevirostris) from 20 consecutive cohorts (1993–2012) at Bimini, Bahamas, showed that certain females faithfully gave birth at this site for nearly two decades. At least six females born in the 1993–1997 cohorts returned to give birth 14–17 years later, providing the first direct evidence of natal philopatry in the chondrichthyans. Long‐term fidelity to specific nursery sites coupled with natal philopatry highlights the merits of emerging spatial and local conservation efforts for these threatened predators.     

Seasonal variation in basal and plastic cold tolerance: Adaptation is influenced by both long‐ and short‐term phenotypic plasticity

Understanding how thermal selection affects phenotypic distributions across different time scales will allow us to predict the effect of climate change on the fitness of ectotherms. We tested how seasonal temperature variation affects basal levels of cold tolerance and two types of phenotypic plasticity in Drosophila melanogaster. Developmental acclimation occurs as developmental stages of an organism are exposed to seasonal changes in temperature and its effect is irreversible, while reversible short‐term acclimation occurs daily in response to diurnal changes in temperature. We collected wild flies from a temperate population across seasons and measured two cold tolerance metrics (chill‐coma recovery and cold stress survival) and their responses to developmental and short‐term acclimation. Chill‐coma recovery responded to seasonal shifts in temperature, and phenotypic plasticity following both short‐term and developmental acclimation improved cold tolerance. This improvement indicated that both types of plasticity are adaptive, and that plasticity can compensate for genetic variation in basal cold tolerance during warmer parts of the season when flies tend to be less cold tolerant. We also observed a significantly stronger trade‐off between basal cold tolerance and short‐term acclimation during warmer months. For the longer‐term developmental acclimation, a trade‐off persisted regardless of season. A relationship between the two types of plasticity may provide additional insight into why some measures of thermal tolerance are more sensitive to seasonal variation than others.     

Environmental change drives long‐term recruitment and growth variation in an estuarine fish

How individuals respond to environmental change determines the strength and direction of biological processes like recruitment and growth that underpin population productivity. Ascertaining the relative importance of environmental factors can, however, be difficult given the numerous mechanisms through which they affect individuals. This is especially true in dynamic and complex estuarine environments. Here, we develop long‐term otolith‐based indices of recruitment and growth for estuary perch Percalates colonorum (Bemm River, Australia), to explore the importance of intrinsic (individual, demographic) and extrinsic (hydrologic, climatic, density‐dependent) factors in driving estuarine fish productivity. Analyses involved a novel zero‐inflated specification of catch curve regression and mixed effects modelling. The 39 years of recruitment and 46 years of growth data, spanning a period of environmental change including severe drought, displayed considerable inter‐annual variation. Recruitment success was strongly related to high freshwater inflows during the spawning season, suggesting that these conditions act as spawning cues for adults and potentially provide favourable conditions for larvae. Individuals displayed age‐dependent growth, with highest rates observed at younger ages in years characterized by warm temperatures, and to a lesser degree, greater magnitude base inflow conditions. We detected systematic among‐year‐class growth differences, but these were not attributable to year class strength, suggesting that environmental conditions experienced by individuals as juveniles can have long‐lasting effects of greater importance to population productivity than density‐dependent growth responses. The primacy of temperature in driving growth variation highlights that under‐appreciated climatic variation can affect estuarine fish productivity through direct physiological and indirect food web mechanisms. We predict that climatic warming will promote individual growth in southerly populations of P. colonorum but concurrently limit recruitment due to forecast reductions in spawning season river discharge. Disparate trait responses are likely in other fishes as they respond to multiple and changing environmental drivers, making predictions of future population productivity challenging.     

The contribution of long‐term isolated water bodies to floodplain fish diversity

1. Floodplains and their water bodies are typical ecotopes of large lowland rivers. The lowland Oder River, Germany, provided a rare opportunity to study fish assemblages of comparable floodplain water bodies differing by >50 years of isolation history. We hypothesised that true floodplain specialists peak in rarely connected water bodies, while frequently flooded waters support tolerant generalists. 2. Three macrohabitats, main channel (MC), temporarily connected and isolated floodplain water bodies, were sampled by electro‐fishing and their fish assemblage characters recorded. 3. Long‐term isolation of floodplain water bodies had a significant effect on the fish assemblage by promoting species preferring still water. Limnophilic and floodplain specialist species significantly increased with isolation. 4. Fish densities, species richness and diversity clearly differed between MC sites and floodplain water bodies. Shannon’s species diversity index peaked in both the MC and isolated waters and was lowest in the temporarily flooded waters where eurytopic fish dominated. 5. The significant gain in abundance and numbers of limnophilic species in the isolated compared to the temporarily flooded water bodies underpinned the significant contribution of long‐term isolated waters to the gamma‐diversity of large floodplain rivers, which should be considered in floodplain rehabilitation.     

Acclimation to ocean acidification during long‐term CO2 exposure in the cold‐water coral Lophelia pertusa

Ocean acidity has increased by 30% since preindustrial times due to the uptake of anthropogenic CO₂ and is projected to rise by another 120% before 2100 if CO₂ emissions continue at current rates. Ocean acidification is expected to have wide‐ranging impacts on marine life, including reduced growth and net erosion of coral reefs. Our present understanding of the impacts of ocean acidification on marine life, however, relies heavily on results from short‐term CO₂ perturbation studies. Here, we present results from the first long‐term CO₂ perturbation study on the dominant reef‐building cold‐water coral Lophelia pertusa and relate them to results from a short‐term study to compare the effect of exposure time on the coral's responses. Short‐term (1 week) high CO₂ exposure resulted in a decline of calcification by 26–29% for a pH decrease of 0.1 units and net dissolution of calcium carbonate. In contrast, L. pertusa was capable to acclimate to acidified conditions in long‐term (6 months) incubations, leading to even slightly enhanced rates of calcification. Net growth is sustained even in waters sub‐saturated with respect to aragonite. Acclimation to seawater acidification did not cause a measurable increase in metabolic rates. This is the first evidence of successful acclimation in a coral species to ocean acidification, emphasizing the general need for long‐term incubations in ocean acidification research. To conclude on the sensitivity of cold‐water coral reefs to future ocean acidification further ecophysiological studies are necessary which should also encompass the role of food availability and rising temperatures.     

Effects of confinement stress and additional zinc treatment on some blood parameters in the dogfish Scyliorhinus canicula

Several blood parameters were studied in the dogfish Scyliorhinus canicula subjected to different confinement conditions (transport and maintenance) and zinc contamination. Confinement stress significantly decreased erythrocyte counts (RBCC), haematocrit (Ht), haemoglobin (Hb), leucocrit (Lt), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC). Mean corpuscular volume (MCV) did not change with this stress and plasma glucose concentration significantly increased. In fish subjected to confinement stress conditions, Zn treatment significantly decreased Hb, MCH and MCHC and plasma glucose concentration. Ht and MCV did not change and Lt and RBCC significantly increased. Results are discussed related to other stress effects and effects of zinc treatment on fish confined in non-stressful conditions.     

Short‐term and long‐term effects of acute kidney injury in chronic kidney disease patients: A longitudinal analysis

We use data from an ongoing cohort study of chronic kidney patients at Salford Royal NHS Foundation Trust, Greater Manchester, United Kingdom, to investigate the influence of acute kidney injury (AKI) on the subsequent rate of change of kidney function amongst patients already diagnosed with chronic kidney disease (CKD). We use a linear mixed effects modelling framework to enable estimation of both acute and chronic effects of AKI events on kidney function. We model the fixed effects by a piece‐wise linear function with three change‐points to capture the acute changes in kidney function that characterise an AKI event, and the random effects by the sum of three components: a random intercept, a stationary stochastic process with Matérn correlation structure, and measurement error. We consider both multivariate Normal and multivariate t versions of the random effects. For either specification, we estimate model parameters by maximum likelihood and evaluate the plug‐in predictive distributions of the random effects given the data. We find that following an AKI event the average long‐term rate of decline in kidney function is almost doubled, regardless of the severity of the event. We also identify and present examples of individual patients whose kidney function trajectories diverge substantially from the population‐average.     

Three decades of longlining in Bimini,Bahamas, reveals long‐term trends in lemon shark Negaprion brevirostris (Carcharhinidae) catch per unit effort

In Bimini, Bahamas, the consistent employment of longlines, beginning in 1982, provided a rare opportunity to explore population trends for large resident sharks. This study assessed three shallow water longline survey periods at this location; 1982–1989, 1992–2002 and 2003–2014, with the aim of determining trends in annual catch per unit effort (CPUE) for an IUCN listed near‐threatened species, the lemon shark Negaprion brevirostris. A general additive model (GAM) was used to analyse the non‐linear annual CPUE values over the entire 32‐year research period. The GAM displayed high variability of annual CPUE, with a peak value of 0·026 N. brevirostris per hook day (hooks day^?1) in 2000. The temporal pattern of CPUE indicated an abundance trend with a complete cycle, from trough to trough, occurring over a period of approximately 18 years. The 1982–1989 survey period saw the highest proportion of mature individuals (19·8%) and the smallest average pre‐caudal length (L_PC; 124·8 cm). The 1992–2002 survey period had the highest average annual CPUE (0·018 hooks day^?1), while the 2003–2014 research period saw largest average L_PC size (134·8 cm) and the lowest average CPUE values (0·009 hooks day^?1) of the entire research period. The long‐term trend identified in this study provides a baseline for future assessment.     

Short‐ and long‐term acclimation patterns of the giant kelp Macrocystis pyrifera (Laminariales,Phaeophyceae) along a depth gradient

The giant kelp, Macrocystis pyrifera, is exposed to highly variable irradiance and temperature regimes across its geographic and vertical depth gradients. The objective of this study was to extend our understanding of algal acclimation strategies on different temporal scales to those varying abiotic conditions at various water depths. Different acclimation strategies to various water depths (0.2 and 4 m) between different sampling times (Jan/Feb and Aug/Sept 2012; long‐term acclimation) and more rapid adjustments to different depths (0.2, 2 and 4 m; short‐term acclimation) during 14 d of transplantation were found. Adjustments of variable Chl a fluorescence, pigment composition (Chl c, fucoxanthin), and the de‐epoxidation state of the xanthophyll cycle pigments were responsible for the development of different physiological states with respect to various solar radiation and temperature climates. Interestingly, the results indicated that phlorotannins are important during long‐term acclimation while antioxidants have a crucial role during short‐term acclimation. Furthermore, the results suggested that modifications in total lipids and fatty acid compositions apparently also might play a role in depth acclimation. In Aug/Sept (austral winter), M. pyrifera responded to the transplantation from 4 m to 0.2 m depth with a rise in the degree of saturation and a switch from shorter‐ to longer‐chain fatty acids. These changes seem to be essential for the readjustment of thylakoid membranes and might, thus, facilitate efficient photosynthesis under changing irradiances and temperatures. Further experiments are needed to disentangle the relative contribution of solar radiation, temperature and also other abiotic parameters in the observed physiological changes.     

Investigating the long‐term legacy of drought and warming on the soil microbial community across five European shrubland ecosystems

We investigated how the legacy of warming and summer drought affected microbial communities in five different replicated long‐term (>10 years) field experiments across Europe (EU‐FP7 INCREASE infrastructure). To focus explicitly on legacy effects (i.e., indirect rather than direct effects of the environmental factors), we measured microbial variables under the same moisture and temperature in a brief screening, and following a pre‐incubation at stable conditions. Specifically, we investigated the size and composition of the soil microbial community (PLFA) alongside measurements of bacterial (leucine incorporation) and fungal (acetate in ergosterol incorporation) growth rates, previously shown to be highly responsive to changes in environmental factors, and microbial respiration. We found no legacy effects on the microbial community size, composition, growth rates, or basal respiration rates at the effect sizes used in our experimental setup (0.6 °C, about 30% precipitation reduction). Our findings support previous reports from single short‐term ecosystem studies thereby providing a clear evidence base to allow long‐term, broad‐scale generalizations to be made. The implication of our study is that warming and summer drought will not result in legacy effects on the microbial community and their processes within the effect sizes here studied. While legacy effects on microbial processes during perturbation cycles, such as drying–rewetting, and on tolerance to drought and warming remain to be studied, our results suggest that any effects on overall ecosystem processes will be rather limited. Thus, the legacies of warming and drought should not be prioritized factors to consider when modeling contemporary rates of biogeochemical processes in soil.     

Fatty acid composition and lipoxygenase metabolism in blood cells of the lesser spotted dogfish, Scyliorhinus canicula.

1. The fatty acid composition of erythrocytes and leucocytes of the elasmobranch, Scyliorhinus canicula, was determined so as to indicate substrate availability for eicosanoid formation. 2. Leucocytes showed a greater degree of fatty acid unsaturation than the erythrocytes, with particularly high levels of docosahexaenoic acid (22:6,n-3). 3. The major eicosanoid precursors, arachidonic acid (20:4,n-6) and eicosapentaenoic acid (20:5,n-3), represented 13.9% and 5.2% of the total fatty acid, respectively, in erythrocytes compared with 10.7% and 6% in leucocytes. 4. Whole blood and isolated leucocytes were stimulated with calcium ionophore, A23187 and the resulting lipoxygenase products separated by reverse phase high performance liquid chromatography. 5. The main lipoxygenase products formed were 6-trans-leukotriene B4, 6-trans-12-epi-leukotriene B4, 5(S),6(R) dihydroxyeicosatetraenoic acid and 5- and 15-hydroxyeicosatetraenoic acid. 6. No leukotriene B4, leukotriene B5, or lipoxins were detected.     

Sexual dimorphisms in the dermal structure of the lesser‐spotted catshark,Scyliorhinus canicula (Linnaeus, 1758)

Sexual dimorphisms in the dermal structures of two elasmobranch species have previously been reported and it has been linked to the use of the mouth by males during copulation. Until relatively recently, the fact, that male Scyliorhinus canicula use their mouths for grasping and biting females during copulation was unknown. This study reveals that not only do adult (M ≥ 525 mm, F ≥ 550 mm) S. canicula show a sexual dimorphism in the epidermis and dermis, but that hatchling S. canicula are born with a sexually dimorphic epidermal layer and this persists into the juvenile stage (M < 525 mm, F < 550 mm). A sexual dimorphism was found in all size classes with both hatchling and juvenile female S. canicula having significantly thicker epidermal layers than hatchling and juvenile male S. canicula. Adult female S. canicula were found to possess both a significantly thicker epidermal and dermal layer than adult male S. canicula. The presence of a sexual dimorphism in the epidermal and dermal layers of adult S. canicula could be directly related to reproductive behaviour in response to the male biting the female prior to copulation.     

Avian ecological succession in the Amazon: A long‐term case study following experimental deforestation

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Low concordance of short‐term and long‐term selection responses in experimental Drosophila populations

Experimental evolution is becoming a popular approach to study the genomic selection response of evolving populations. Computer simulation studies suggest that the accuracy of the signature increases with the duration of the experiment. Since some assumptions of the computer simulations may be violated, it is important to scrutinize the influence of the experimental duration with real data. Here, we use a highly replicated Evolve and Resequence study in Drosophila simulans to compare the selection targets inferred at different time points. At each time point, approximately the same number of SNPs deviates from neutral expectations, but only 10% of the selected haplotype blocks identified from the full data set can be detected after 20 generations. Those haplotype blocks that emerge already after 20 generations differ from the others by being strongly selected at the beginning of the experiment and display a more parallel selection response. Consistent with previous computer simulations, our results demonstrate that only Evolve and Resequence experiments with a sufficient number of generations can characterize complex adaptive architectures.     

Predicting ecosystem carbon balance in a warming Arctic: the importance of long‐term thermal acclimation potential and inhibitory effects of light on respiration

The carbon balance of Arctic ecosystems is particularly sensitive to global environmental change. Leaf respiration (R), a temperature‐dependent key process in determining the carbon balance, is not well‐understood in Arctic plants. The potential for plants to acclimate to warmer conditions could strongly impact future global carbon balance. Two key unanswered questions are (1) whether short‐term temperature responses can predict long‐term respiratory responses to growth in elevated temperatures and (2) to what extent the constant daylight conditions of the Arctic growing season inhibit leaf respiration. In two dominant Arctic species E riophorum vaginatum (tussock grass) and B etula nana (woody shrub), we assessed the extent of respiratory inhibition in the light (R _L/R _D), respiratory response to short‐term temperature change, and respiratory acclimation to long‐term warming treatments. We found that R of both species is strongly inhibited by light (averaging 35% across all measurement temperatures). In E . vaginatum both R _L and R _D acclimated to the long‐term warming treatment, reducing the magnitude of respiratory response relative to the short‐term response to temperature increase. In B . nana, both R _L and R _D responded to short‐term temperature increase but showed no acclimation to the long‐term warming. The ability to predict plant respiratory response to global warming with short‐term temperature responses will depend on species‐specific acclimation potential and the differential response of R _L and R _D to temperature. With projected woody shrub encroachment in Arctic tundra and continued warming, changing species dominance between these two functional groups, may impact ecosystem respiratory response and carbon balance.