Fine-scale differences in diel activity among nocturnal freshwater planarias (Platyhelminthes: Tricladida)

<p>Abstract</p> <p>Background</p> <p>Although most freshwater planarias are well known photonegative organisms, their diel rhythms have never been quantified. Differences in daily activity rhythms may be particularly important for temperate-climate, freshwater planarias, which tend to overlap considerably in spatial distribution and trophic requirements.</p> <p>Methods</p> <p>Activity of stress-free, individually tested young adults of three common planarian species was recorded at 3-h intervals in a 10-d experiment under natural sunlight and photoperiod during autumnal equinox (D:L ~12:12). Individual activity status was averaged over the 10-d experiment, each tested individual thus serving as a true replicate. Twelve individuals per species were tested. Food was provided every 36 h, resulting in alternating day- and nighttime feeding events. Activity during the first post-feeding h was recorded and analyzed separately. Statistical procedures included ANOVAs, correlations, and second-order analyses of angles.</p> <p>Results</p> <p><it>Dugesia (= Girardia) tigrina </it>Girard 1850 exhibited clear nocturnal behavior, <it>Dugesia (= Schmidtea) polychroa </it>Schmidt 1861 was predominantly but not exclusively nocturnal, and <it>Polycelis tenuis </it>Ijima 1884 was relatively more active from midnight through noon. Species-specific activity peaks were statistically similar, with peaks at dawn for <it>P. tenuis </it>and just before midnight for the two dugesiids; however, <it>D. tigrina </it>was comparatively more active in the early night hours, while <it>D. polychroa </it>was more active than <it>D. tigrina </it>during daytime. <it>D. tigrina </it>also responded less readily to daytime food addition. <it>P. tenuis </it>remained poorly active and unresponsive throughout the experiment. Individual variability in diel behavior was highest for <it>D. polychroa </it>and lowest for <it>D. tigrina. P. tenuis</it>'s general low degree of activity and late activity peak in the experiment may be related to a strong reliance on external stimuli.</p> <p>Conclusions</p> <p>The tested species are mainly nocturnal, consistent with their photonegative characteristics. The fine-scale differences in diel behavior among these three triclad species may not be sufficient to allow coexistence in the wild, with the nonnative <it>D. tigrina </it>eventually displacing <it>D. polychroa </it>and <it>P. tenuis </it>in many European waters. The link between planarian diel rhythms and ecological characteristics are worth of further, detailed investigation.</p

Length–weight relationships for some plecoptera and ephemeroptera from a carbonate stream in central Apennine (Italy)

The relationship between dry weight and body length for larvae of Plecoptera (Leuctra spp., Isoperla grammatica, Nemoura cinerea) and Ephemeroptera (Baetis spp., Habrophlebia fusca, Paraleptophlebia submarginata, Ecdyonurus helveticus, Rhithrogena semicolorata), collected from a carbonate stream in the Apennine (central Italy), is reported. The power equation f(x) = Ax B has been applied to fit the curves of dry weight vs. body size (length) in the ranges 0.03–13.00 mg and 2–14 mm, respectively; a total of 674 larvae were examined. The power model was in very good agreement with experimental data. Moreover, the error between measured and estimated weight was in the 4–20% range. The data on Isoperla grammatica, Leuctra spp., Rhithrogena semicolorata and Baetis spp. were compared to those in a previous study in a different geographical setting (south-western Germany's Black Forest) obtaining similar results but with lower errors. We used and compared two methods: the weighted least-square method (WLS) and an analysis of covariance (ANCOVA). The values of the A and B coefficients obtained with the two methods were very similar (<6% discrepancy for either A or B). We found the best fits for all the examined Plecoptera (species, genus, and order level), while the results for Ephemeroptera were varied, with loose fits at the order level and also for Leptophlebiidae collectively considered

A modification of the leaf-nets method for sampling benthic invertebrates in spring habitats

The full ecological potential of spring habitats remains relatively unexplored mostly because of the lack of standardized sampling procedures and difficulties to collect representative biological samples, especially in small-sized springs. Recent studies on sampling methodologies in spring habitats indicated that a modified Surber net with a reduced frame area, reliably describes the structure and composition of spring communities. This method, however, is very invasive and may severely impact the spring, especially when a large number of samples is required. The paper presents a new quantitative method (leaf-nets) for sampling crenic invertebrates which combines a rather high efficiency with negligible impacts on spring habitat structure and biota. The effectiveness of the new methodology was tested in a medium-size rheocrene spring in Central Apennine, where spring assemblages were sampled in parallel with a modified Surber net and with the new method. Taxa richness and density were higher in the Surber net, while no between-method differences were recorded for the number of insect taxa and Simpson diversity. Furthermore, the overall functional organization of Surber net and leaf-nets assemblages was very similar. The new method sampled only 25% of the individuals cumulatively collected, but 75% of the total richness, with a good representation of the structure and the functional organization of spring assemblages. In comparison with the Surber net, the negligible loss of information of the new method is highly compensated by its minor invasivity, lower impacts on spring microhabitats and invertebrate populations and by its higher versatility. Leaf-nets could also be used to assess leaf-detritus breakdown in springs, thus allowing a better ecological characterization of these ecosystems. </p

A modification of the leaf-bags method to assess spring ecosystem functioning: benthic invertebrates and leaf-litter breakdown in Vera Spring (Central Italy)

The evaluation of leaf detritus processing (decomposition and breakdown) is one of the most simple and cost-effective method to assess the functional characteristics of freshwater ecosystems. However, in comparison with other freshwater habitats, information on leaf litter breakdown in spring ecosystems is still scarce and fragmentary. In this paper, we present results of the first application of a variant of the leaf-bags method to assess structure of macroinvertebrate assemblages and leaf-litter breakdown in a Central Apennines (Italy) cold spring which was investigated from July 2016 to October 2016. Notwithstanding the stable conditions of almost all hydrological and physico-chemical parameters, we found significant temporal differences in (i) % of mass loss of poplar leaves (ii) number of Ephemeroptera, Plecoptera and Trichoptera taxa, (iii) shredder and predator densities. We demonstrate that detritus processing in cold springs may be faster than or as fast as in warmer streams/rivers. Shredders activity and biocoenotic interactions, rather than temperature and nutrients load, were the main drivers of the process. A routine application of the modified leaf-bags may contribute to expand our knowledge on detritus processing in cold springs and may help to predict impacts of climate warming on freshwater ecosystem functioning

Assessment of river quality within the context of the EU's water framework directive (2000/60/EC): the RiverNet Experiences

EnThe purpose of the EU's Water Framework Directive (WFD)is the achievement of ecological good status for all its superficial water bodies and courses.However,the most controversial and difficult aspect is the choice of an appropriate method to define a “reference condition ”,the expected value upon which comparisons are to be made and quantitatively expressed as EQR metric (ecological quality ratio).A major burden is the adjustment of national standards to assess the quality of aquatic habitats according to the technical specifications explicitly stated in the WFD.This aspect is also one of the major objectives within the RiverNet project.We compared standard methods used in Italy (not compliant with WFD requirements)with those currently under study by the pan-European intercalibration panel.Data spanning one year (2002)from the Abruzzo monitoring programwere used.Data from 229 samples (78 sites and 38 water courses)were reanalyzed using both Italian (LIM,IBE,SECA)and other metrics (family richness,BMWP,ASPT,EPT,EPT%).Resulting ecological status assessments were compared quantitatively and expressed as EQR.Indices based on benthic invertebrates were closely interrelated ($R2==0.71 –0.88 for pairwise correlations),and performed better than the abiotic LIM index.The BMWP index seems better suited than the non-WFD-compliant IBE index to describe ecological status.Though the dataset was relatively limited,we were able to identify 13 class-1 (least impacted)sites that can be used as reference sites for Abruzzo.Additionally,EQR-based range and threshold values for each tested metric were quantified for the high, good and moderate quality lasses.Utilization of historical data may be a cost-and time-effective approach potentially leading to a regional and nationwide establishment of reference conditions and range quality-class values for riverine systems

predation by dugesia polychroa platyhelminthes tricladida prevents the establishment of physa acuta gastropoda pulmonata in hard substratum habitats

Despite half a century of research on planarian-gastropod interactions, the population-level impact of planarian predation on littoral pulmonates is not well known. We have quantified the predation of the common lacustrine planaria Dugesia polychroa Schmidt on the ubiquitous snail Physa acuta Drap., a potential keystone grazer in benthic littoral communities, in a high-replicate laboratory experiment. Planarian predation pressure was maintained constant, and experimental populations of P. acuta were size-structured simulating young-rich small groups (re)colonising the habitat (e.g. after release from predation). D. polychroa caused a quick (week 2) reduction in the density of hatchlings and juveniles, followed by significant reduction in the numbers of young (at the onset of reproductive age) and larger, reproductive-age adults (week 3). Planarias did not have any effect on the size of reproductive-age large adults, but oviposition decreased significantly in week 2, and all P. acuta populations in planarian-present aquaria went extinct within six weeks. Dugesiidinduced extinction mainly occurred by precluding population turnover. The results strongly suggest that active predation by D. polychroa on P. acuta can be high under some environmental conditions, effectively preventing the (re)establishment of small, colonising populations of P. acuta in hard-substratum habitats

Corrigendum to: Structure, functional organization and biological traits of macroinvertebrate assemblages from leaf-bags and benthic samples in a third-order stream of Central Apennines (Italy) [Ecological Indicators 46 (2014) 84–91]

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Low elasticity of thyroid nodules at ultrasound elastography is correlated with malignancy, degree of fibrosis and high expression of galectin-3 and fibronectin-1

ackground: Thyroid ultrasound (US) elastography provides an estimation of tissue stiffness and is helpful to differentiate malignant from benign lesions. Tissue proprieties and molecules causing stiffness are not established. The aim of the study was to correlate US elastography findings with tissue properties in thyroid nodules. Methods: A total of 115 thyroid nodules from 112 patients who underwent surgery for the presence of Thy 3 (indeterminate) cytology (n = 67), Thy 4-5 (suspicious - indicative of carcinoma) cytology (n = 47), or large goiter in the presence of Thy 2 cytology (n = 1) and suspicious US features were examined by US elastography. Tissues obtained after surgery were characterized for cell number, microvessel density, fibrosis, and expression of galectin-3 (Gal-3) and fibronectin-1 (FN-1). Results: Low elasticity on qualitative US elastography (LoEl) was found in 66 nodules (one benign and 65 carcinomas); high elasticity (HiEl) was found in 49 nodules (46 benign and three carcinomas; p &lt; 0.0001). Quantitative analysis, performed in 24 nodules and expressed as elastic ratio between the strain of the nodule and that of the surrounding thyroid parenchyma, showed a mean of 1.90 (interquartile range [IQR] 1.18-2.77) in 14 nodules with LoEl, and a mean of 1.01 (IQR 0.91-1.10) in 10 nodules with HiEl (p = 0.002). Stiffness did not correlate with cell number and was inversely correlated with microvessel density. Fibrosis was higher in nodules with LoEl than in those with HiEl (p = 0.009) and in carcinomas than in benign nodules (p = 0.02). Fibrosis was higher in nodules with high expression of Gal-3 (p &lt; 0.001) and FN-1 (p = 0.004). Fibrosis and expression of Gal-3 and FN-1 were higher in the classic compared with the follicular variant of papillary thyroid carcinoma and lower in follicular adenomas. Conclusions: Low elasticity at US elastography is highly correlated with malignancy. Nodule stiffness is correlated with fibrosis and expression of Gal-3 and FN-1. These features are more evident in the classic than in the follicular variant of papillary thyroid carcinoma

Assessment of river quality within the context of the EU's water framework directive (2000/60/EC): the RiverNet Experiences

EnThe purpose of the EU's Water Framework Directive (WFD)is the achievement of ecological good status for all its superficial water bodies and courses.However,the most controversial and difficult aspect is the choice of an appropriate method to define a “reference condition ”,the expected value upon which comparisons are to be made and quantitatively expressed as EQR metric (ecological quality ratio).A major burden is the adjustment of national standards to assess the quality of aquatic habitats according to the technical specifications explicitly stated in the WFD.This aspect is also one of the major objectives within the RiverNet project.We compared standard methods used in Italy (not compliant with WFD requirements)with those currently under study by the pan-European intercalibration panel.Data spanning one year (2002)from the Abruzzo monitoring programwere used.Data from 229 samples (78 sites and 38 water courses)were reanalyzed using both Italian (LIM,IBE,SECA)and other metrics (family richness,BMWP,ASPT,EPT,EPT%).Resulting ecological status assessments were compared quantitatively and expressed as EQR.Indices based on benthic invertebrates were closely interrelated ($R2==0.71 –0.88 for pairwise correlations),and performed better than the abiotic LIM index.The BMWP index seems better suited than the non-WFD-compliant IBE index to describe ecological status.Though the dataset was relatively limited,we were able to identify 13 class-1 (least impacted)sites that can be used as reference sites for Abruzzo.Additionally,EQR-based range and threshold values for each tested metric were quantified for the high, good and moderate quality lasses.Utilization of historical data may be a cost-and time-effective approach potentially leading to a regional and nationwide establishment of reference conditions and range quality-class values for riverine systems