Sympatric coevolution of the trophic niche of two detritivorous isopods, Asellus aquaticus and Proasellus coxalis

The role of 16 species of microfungi in the potential trophic niche of populations of Asellus aquaticus (L.) and Proasellus coxalis Dolff. collected in both sympatry and allopatry was determined in the laboratory. Animals and fungi were collected in three woodland streams similar as to geographic location and hydrogeologic, physical and chemical features. The fungi were offered as the sole food source to the animals for 50 d. Young animals, born in the laboratory, were tested for their trophic potential. Sympatric A. aquaticus and P. coxalis had a much more differentiated potential trophic niche than allopatric populations. In particular, the sympatric species had a potential overlap in the use of 25% of the tested fungi, while allopatric species had a potential overlap of 75% of the fungi. The two species from sympatric locations were specialized on fungal species not very common in nature, while more common fungi were used without distinction by both species. The exclusiveness of each fungal species for the isopods living in sympatry increased inversely to its frequency in nature. The results suggest a possible effect of co-occurrence on the character displacement shown by sympatric populations and support the hypothesis of coevolutionary trophic partitioning between them. The results also imply that the importance of the fungi in the co-occurrence of the isopod species is greater than suggested by the small biomass of the fungi

Perfluorooctanoic acid-induced cellular and subcellular alterations in fish hepatocytes

Liver perfluorooctanoic acid (PFOA) pathophysiology and related morphofunction disturbances were studied in common carp at the cellular and subcellular level and with box-counting fractal analysis of ultrathin sections to assess the effect of PFOA exposure on hepatocyte structure complexity and heterogeneity. Three experimental groups were investigated: unexposed; low exposure (200 ng L-1 PFOA); high exposure (2 mg L-1 PFOA). PFOA-exposed cells showed differences from controls at both tested concentrations, manifested mainly as cloudy swelling and reversible vacuolar degeneration. Subcellular modifications primarily involved mitochondria and secondarily endoplasmic reticulum, with evidence of increased subcellular turnover. The alterations were consistent with oxidative stress related pathophysiology. Fractal analysis discriminated exposed from unexposed fish and low from high PFOA exposure based on lacunarity and fractal dimension, respectively. The absence of irreversible organelle alterations and apoptosis/necrosis, along with the increase of cellular complexity, led to the conclusion that the patterns observed represented an adaptive recovery response

A Review and Synthesis of Bivariate Non-Linear Models to Describe the Relative Variation of Ecological, Biological and Environmental Parameters

There is a plethora of non-linear models to describe bivariate relationships related to ecological, biological and environmental problems, and this makes difficult to have a general aspect about the suitable models for a new-born dataset. Additionally, there is a special interest for bivariate non-linear models which can describe the relative variation of the dependent variable (NLR models) (i.e. these models provide a restricted range of values between 0 and 1) because they can easily be adjusted to fit different datasets which describe the same relationship. The aim of this study is to provide a review and synthesis of NLR models which can be used to describe bivariate relationships which follow bell-shaped, simple-double sigmoid, bilinear and periodical patterns. This attempt aims to save time and effort for the selection of a NLR model based on five steps (a) preparation of data, (b) visual identification of the suitable model based on pre-constructed graphs, (c) a starting point using the simpler form (base function) of the selected models which are given in complex general forms, (d) directions to increase the number of coefficients in order to improve fitting and (e) techniques to modify the given NLR models in order to derive new ones with inverted patterns

Manila clam introduction in the Sacca di Goro Lagoon (Northern Italy): ecological implications

The manila clam was introduced in 1986 in the Sacca di Goro lagoon (Po River Delta, northern Italy) and in a few years became one of the backbone of the local economy. Few years later, the lagoon was affected by macroalgal blooms, followed by the biomass breakdown which impacted the clam farming, with mass mortality in summer. From late 1987 to 1994, an intensive, monthly-based monitoring plan of water column was thus performed, aiming at analyzing salinity, dissolved oxygen, chlorophyll a and nutrient patterns in a grid of sampling stations, with respect to hydrodynamics and freshwater inputs. Later on, monitoring of spatial distribution, biomass evolution and ecophysiology of the dominant macroalgal community was performed (1990-1998), together with experiments focusing on macroalgal production and factors controlling macroalgal growth and decay. Furthermore, the role of clams in coupling benthic and pelagic processes was addressed as a possible feedback loop in the lagoonal ecosystem. Regular monitoring was afterwards flanked by an experimental approach aiming at more detailed studies of how clams affect benthic processes, in particular aerobic and anaerobic respiration, nutrient recycling, the regulation of denitrification and the analysis of nitrogen cycling within farmed areas (1993-2005). More recently, different European projects addressed the relationships between environmental and socio-economic issues in the clam farming management. In this review we summarize the main outcomes of these research activities with the overall aim of quantifying, at the lagoon scale, the role of the farmed species as regulators of some of the multiple processes involved in the ecosystem metabolism and biogeochemistry. Special emphasis is given to how clams affect uptake, dissipation and recycling pathways of nutrients, especially nitrogen. Overall, the clam farming system is analyzed for its implications in the whole lagoon metabolism and for possible ecological feedbacks which in turn can impact the local socio-economic system

Land use change effects on ecosystem services of river deltas and coastal wetlands: case study in Volano–Mesola–Goro in Po river delta (Italy)

The landscape of river deltas and coastal wetlands is under a continuous alteration due the combined effects of human and natural factors. The aim of the study is to analyze the Land Use/Land Cover (LULC) changes and associated Ecosystem Services (ESs) of a protected wetland area in the Po river delta (Northern Italy). A combination of methodologies which take into account both the assessment of socio-economic benefits (approach of ESs) and the monitoring of ecosystems attributes (LULC change analysis using transition matrices TMs) were used by comparing the changes observed during two periods (1954–1976 and 1976–2008) described by different environmental protection governance. The period 1954–1976 is described by extensive land reclamations while the period 1976–2008 by significant efforts for applying environmental protection measures. The results highlighted an extensive loss of vegetated wetlands due to direct human interventions (croplands and urban areas expansion) during the first period. The direct human intervention was significantly reduced during the second period. However, vegetated wetlands losses did not follow an analogous reduction probably due to indirect human interventions and natural factors. TMs identified the exact LULC conversions while the ESs approach highlighted the significant economic impact of vegetated wetlands’ losses. Waste treatment was the most important ES of the specific system providing approximately 70 % of the estimated natural capital value. The proposed combination of the selected methods (TMs and ESs) provides a detailed description of landscape changes and their economic impact, which can be used as decision support tool for landscape conservation policies

Common carp Cyprinus carpio responses to sub-chronic exposure to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is an important and diffuse perfluorinated alkylated substance, but knowledge of the toxicological effects of this endocrine disrupter in fish is limited. Adult common carp Cyprinus carpio, L. were exposed to 200 ng/l (a concentration reported in impacted aquatic ecosystems) and 2 mg/l PFOA solutions in a flowthrough system for 56 days to determine tissue accumulation and histological alterations of the primary target organs. PFOA was extracted from blood, gill, liver, muscle, kidney, gonad, and brain by an ion-pairing liquid extraction procedure and quantified using high performance liquid chromatography with electrospray ionization tandem mass spectrometry. The limit of detection (LOD) was 0.4 ng/g wet weight (ww). PFOAwas not detectable in unexposed fish or in fish exposed to 200 ng/l, but was >LOD in most samples of carp exposed to 2 mg/l. Mean PFOA concentration ranged from 0.5 to 65 ng/g ww, depending on the tissue, with highest levels in the blood and liver. There were no significant differences in condition factor, hepato-somatic index, or gonado-somatic index among the fish of the three groups. Histological, histochemical, and immunohistochemical staining was performed on sections of liver and gonad. Occurrence of atretic oocytes and a paucity of spermatozoa were documented in carp treated with 2 mg/l PFOA. Exposed fish did not show gross hepatic anomalies, but there was enhancement of hepatocytes in proliferation (positive to anti-PCNA antibody) compared to controls

Perfluorooctanoic Acid Exposure Assessment on Common Carp Liver through Image and Ultrastructural Investigation

Perfluorooctanoic acid (PFOA) poses particular concern as an emerging pollutant in both surface and ground waters. Fish, as a natural inhabitant of these waters and being highly representative of vertebrates, represents an ideal animal model to assess the toxic effects of PFOA. Hereby, liver microscopic texture was comparatively evaluated in individuals of common carp subchronically exposed to PFOA using grayscale differential box counting, a fractal analysis method. Furthermore, liver cytoplasmic glycogen areas and ultrastructure were also evaluated and compared to the image analysis findings. Redundancy Analysis was performed to assess, in summary, how much the variation of fractal dimension and lacunarity was explained by the concentration of PFOA in liver, the mass of liver and the number of proliferating cell nuclear antigen (PCNA)-immunoreactive nuclei. Treatment group ordination was better determined by fractal dimension than lacunarity. Interestingly, a significant complexity increase was associated with the modification of liver microscopic texture due to PFOA exposure. This complexity increase was related to “cloudy swelling”, possibly representing a primarily adaptive strategy against PFOA challenge, rather than a slight, reversible form of degeneration as traditionally proposed. The occurrence of endoplasmic reticulum stress, unfolded protein reaction and hormetic response was proposed and discussed

A size-age model based on bootstrapping and Bayesian approaches to assess population dynamics of Anguilla anguilla L. in semi-closed lagoons

A size-age modelling technique is presented for assessing the vital rates, stock and recruitment of eel populations in semi-closed lagoons with fully monitored migration of silver eels. Data for yellow and silver European eels (Anguilla anguilla L.) were obtained in 2011 from the Comacchio lagoon (Italy). The analysis was performed in three steps: (i) correction of yellow eel data, which are affected by the fyke nets selectivity during samplings, (ii) estimation of survival curve, stock, recruitment and metamorphosis rates of the population (calibration using data from 2011) and (iii) validation of the model using the observed amount of silver eel migrating population of the next year. A bootstrap procedure was used to assess the level of uncertainty for each parameter using the 95% intervals of the highest posterior density distribution HPDD (Bayesian approach). The measured abundance of silver eels was 0.56 ind·ha-1, while the yellow eel abundance and recruitment were estimated by the model for 2011 at 8.77 ind·ha-1 and 5.99 ind. ha-1 respectively. The model performance during validation was satisfactory as the observed total mass of migrating population of 2012 (3777 kg) was inside the 95% HPDD intervals (3197-3839 kg) of model's predictions. The estimated stocks and recruitment were at least ten times lower from the respective estimations of previous studies of 1989 highlighting the crucial conditions of the population. The proposed modelling approach can provide significant information about eel population conditions, facilitating the evaluation of a range of management options in the context of eel conservation plans