Is landscape of fear of macroinvertebrate communities a major determinant of mesopredator and prey activity?

Macroinvertebrate foragers play an important role on the trophic structures of freshwater environments, and multiple trophic levels occur among macroinvertebrate communities providing very interesting scenarios for testing scientific hypotheses. One of the most intriguing aspect to understand is the role played by the landscape of fear (LOF) on macrobenthos density and activity. With this pilot study we wanted to test if LOF at the macrobenthos community levels plays a role in determining the density of both prey and mesopredators. During two consecutive years, we evaluated, with both day and night surveys, the density of two mesopredator triclad species and of one detritivore prey crustacean species, and we compared them to the number of respective predators occurring in the macroinvertebrate community. LOF levels at the macroinvertebrate community did not reduce the abundance of the target taxa. One of the triclad species was instead positively related to the levels of LOF assessed for it on the basis of the available knowledge. The broad implication of the research is that the abundance of freshwater macroinvertebrates is not mainly linked to the predation risk at the community level, suggesting that also for researches on macrobenthos LOF analyses should take in consideration the role of top predators

The worldwide physical height datum project

AbstractThe definition of a common global vertical coordinate system is nowadays one of the key points in Geodesy. With the advent of GNSS, a coherent global height has been made available to users. The ellipsoidal height can be obtained with respect to a given geocentric ellipsoid in a fast and precise way using GNSS techniques. On the other hand, the traditional orthometric height is not coherent at global scale. Spirit levelling allows the estimation of height increments so that orthometric heights of surveyed points can be obtained starting from a benchmark of known orthometric heights. As it is well known, this vertical coordinate refers to the geoid, which is assumed to be coincident to the mean sea level. By means of a tide gauge, the mean sea level is estimated and thus a point of known orthometric height is defined. This assumption, which was acceptable in the past, became obsolete given the level of precision which is now required. Based on the altimetry observation, one can precisely quantify the existing discrepancy between geoid and mean sea level that can amount to 1 ÷ 2 m at global scale. Therefore, different tide gauges provide biased estimates of the geoid, given the discrepancy between this equipotential surface and the mean sea level. Also, in the last years, another vertical coordinate was used, the normal height that was introduced in the context of the Molodensky theory. In this paper, a review of the existing different height systems is given and the relationships among them are revised. Furthermore, an approach for unifying normal height referring to different tide gauges is presented and applied to the Italian test case. Finally, a method for defining a physical height system that is globally coherent is discussed in the context of the definition of the International Height Reference System/Frame, a project supported by the Global Geodetic Observing System of the International Association of Geodesy (IAG). This project was established in 2015 during the XXVI IAG General Assembly in Prague as described in IAG Resolution no. 1 that was presented and adopted there

Do Salamanders Limit the Abundance of Groundwater Invertebrates in Subterranean Habitats?

Several species of surface salamanders exploit underground environments; in Europe, one of the most common is the fire salamander (Salamandra salamandra). In this study, we investigated if fire salamander larvae occurring in groundwater habitats can affect the abundance of some cave-adapted species. We analyzed the data of abundance of three target taxa (genera Niphargus (Amphipoda; Niphargidae), Monolistra (Isopoda; Sphaeromatidae) and Dendrocoelum (Tricladida; Dedrocoelidae)) collected in 386 surveys performed on 117 sites (pools and distinct subterranean stream sectors), within 17 natural and 24 artificial subterranean habitats, between 2012 and 2019. Generalized linear mixed models were used to assess the relationship between target taxa abundance, fire salamander larvae occurrence, and environmental features. The presence of salamander larvae negatively affected the abundance of all the target taxa. Monolistra abundance was positively related with the distance from the cave entrance of the sites and by their surface. Our study revealed that surface salamanders may have a negative effect on the abundance of cave-adapted animals, and highlited the importance of further investigations on the diet and on the top-down effects of salamanders on the subterranean communities

The stenoendemic cave-dwelling planarians (Platyhelminthes, Tricladida) of the Italian Alps and Apennines: Conservation issues

Despite being a fundamental component of biodiversity, several highly diverse taxa of aquatic invertebrates are still poorly known and poorly considered in protection programs. This is the case especially of several invertebrate species that inhabit groundwater. In this environment, invertebrates play significant roles in ecosystem services closely connected to the usefulness of these systems for human welfare and survival. The groundwater biodiversity of continental Italy is largely unknown and its importance is neglected in national and regional legislation. One of the most poorly studied groups of Italian groundwater fauna are planarians (Platyhelminthes, Tricladida). Most known species are endemic to small, single karst areas or a single cave, their geographic range never having been investigated in detail after the original description. The aims of this study are i) to provide the first conservation assessment of cave-dwelling planarians in the Italian Alps and Apennines, whose status is at present Not Evaluated in IUCN categories and ii) to evaluate which environmental constraints, including potential threats, possibly affect the occurrence of the species within different cave systems. Our results suggest that most of the cave-dwelling planarian species of continental Italy are threatened by water pollution and habitat destruction/alteration; moreover, datasets underline that there is a considerable conservation issue concerning stenoendemic planarians that may involve other cave-dwelling invertebrates with narrow geographic ranges. Generally, the underground habitat of most surveyed species appears to be deeply compromised and changed since the first species description

Detection of non-consumptive effects of predation and intraspecific aggression in fire salamander larvae: Environmental issues

The identification of injury causes may reveal important insights on the factors that influence intra and interspecific predation pressures. In this study we evaluated the proportion of injuries occurring in fire salamander larvae (Salamandra salamandra) in caves and epigean springs to understand the factors determining non-consumptive effects that may affect larval survival. We surveyed 25 sites (13 cave pools, 12 spring pools) during the day. We applied two consecutive removal samplings to collect fire salamander larvae and examined every removed larva to detect if it had injuries and we evaluated the proportion of the injured larvae on the total number of collected larvae. For each site we recorded different environmental variables including predator occurrence and prey density. The proportion of injured larvae was significantly linked only to predators occurrence. Our results show that interspecific predation pressure is a major source of non-consumptive effects that may affect larval survival Overall, our study underlines the role that environmental features may play on the non-consumptive effects of selective pressures that affect larval survival. Predator occurrence determines the levels of non-consumptive effects and larval survival across their developmental cycle. These results deriving from a field survey could furnish useful insights for further experimental studies

Study on the differences of BMI between olms found in cave and the ones sampled in spring

The olm (Proteus anguinus) is a blind amphibian, depigmented and with an extremely reduced metabolism. These are adaptations to cave life that allow the animals to exploit this hostile (from a human perspective) habitat. Adaptations to cave life, should prevent successful exploitation of the external environment. However, although the Proteus is a cave animal, it has been reported by some authors in the spring environment, Our previous results showed that this presence, would seem not to be random, in but linked to very specific factors such as hydroperiod the absence of potential predators. In the light of these results, we have conducted a study with the aim of verifying whether the Proteus benefits from exploiting the trophic resources occurring in springs. Since June 2020 we have sampled 64 springs and 12 caves in the Monfalcone province, each olm found during the sampling was photographed, measured and weighed. A total of 73 different olms were analyzed and the Body Mass Index (BMI) was calculated for each individual. Olms found in springs had a significantly higher BMI than those found in caves. The BMI of springs’ olms was significantly related to amount of the trophic available, evidencing that they took advantages from exploiting the external environment. These results contribute to support the hypothesis of the non-random presence of the Proteus in the spring environment, the olm, in fact, seem to benefit from this type of habitat taking advantage of the greater number of resources present in it

Activity of the olm (Proteus anguinus) in surface habitats: ecological and evolutionary insights

The olm is considered as a classic example of troglobiont organism. However, in the past different observations of individuals of the typical troglomorphic populations have been reported for springs of Venetia Giulia. The aim of this work is to point out the non-random active use of surface habitats by the olm, providing a comparison with the occurrence observed in caves and performing an assessment of factors favouring ecotone habitats exploitation. Since 2020 we started multiple day and night surveys of olms in both springs and caves. Each spring and cave habitat monitored has been characterised by respect to abiotic and biotic features, including planktonic and benthic prey availability. We detected the olm at least once in 10 springs, with a maximum of 9 individuals occurring together. Detection probability in springs and caves was similar. Spring habitats provided higher density of potential prey available. Olms seems to prefer springs without predator fish and temporary hydroperiod. We recorded in one spring a larva of 3.5 cm which could be the smallest ever recorded in the field. We suggest that epigean habitats and borders with surface may have an underestimated importance for animals adapted to subterranean environments, including the olm. Our results stimulate for testing if exploitation of ecotones between surface and groundwater can lead to differentiation in populations/subpopulations of stygobiont animals

Correzioni gravimetriche per la rete di livellazione geometrica italiana: stato dell’arte e l’esempio della Provincia di Trento

Riassunto Il sistema di riferimento altimetrico ufficiale italiano è definito attraverso una rete di livellazione geometrica materializzata e periodicamente rilevata dall’Istituto Geografico Militare (IGM). Le quote dinamiche, ortometriche e normali dei capisaldi di una rete di livellazione si ottengono dalla compensazione ai minimi quadrati dei dislivelli geometrici osservati, opportunamente corretti per gli effetti di gravità. Il Politecnico di Milano (POLIMI), nell’ambito di una convenzione con l’IGM, sta effettuando il calcolo delle correzioni (dinamiche, ortometriche e normali) da apportare alle nuove osservazioni di livellazione eseguite nel contempo dall’IGM sull’intero territorio nazionale per l’aggiornamento del sistema di altezze italiano. I valori di gravità necessari al calcolo delle correzioni sono ricavati dal database utilizzato per il nuovo Geoide Italiano. Il Servizio Catasto della Provincia Autonoma di Trento in accordo con IGM e POLIMI partecipa all’acquisizione delle osservazioni della sotto-rete trentina e al successivo calcolo delle relative correzioni. Lo stato dell’arte nella definizione del sistema di riferimento delle altezze, con richiami sul calcolo delle correzioni gravimetriche classiche e su una nuova formulazione sviluppata di recente nell’ambito della teoria di Molodensky costituiscono l’oggetto della presente comunicazione insieme ai risultati preliminari ottenuti sui dati del Trentino.Abstract The official italian height system is defined through a spirit leveling network periodically surveyed by the Istituto Geografico Militare (IGM). Dynamic, orthometric and normal heights of the network benchmarks are obtained form the least squares adjustment of the observed height differences, properly corrected for the gravity effects. In agreement with IGM, the Politecnico di Milano (POLIMI) is computing the corrections (dynamic, orthometric and normal) for the new spirit leveling observations, carried out in the meanwhile by the IGM to update the italian height datum. The gravity observations needed to evaluate the corrections are obtained from the same database used for the Italian Geoid. The Cadastral service of Provincia Autonoma di Trento in agreement with IGM and POLIMI is involved in the observation collection of the Trentino sub network as well as in the connected correction computation. The presentation is about the state of the art in the definition of the italian height datum and a short review on the gravity correction formulas as well as on a new formulation of the normal correction term in the framework of Molodensky’s theory. Preliminary results on the Trentino sub network will be presented as well

Precision measurement of the neutrino velocity with the ICARUS detector in the CNGS beam

During May 2012, the CERN-CNGS neutrino beam has been operated for two weeks for a total of 1.8 10^17 pot in bunched mode, with a 3 ns narrow width proton beam bunches, separated by 100 ns. This tightly bunched beam structure allows a very accurate time of flight measurement of neutrinos from CERN to LNGS on an event-by-event basis. Both the ICARUS-T600 PMT-DAQ and the CERN-LNGS timing synchronization have been substantially improved for this campaign, taking ad-vantage of additional independent GPS receivers, both at CERN and LNGS as well as of the deployment of the "White Rabbit" protocol both at CERN and LNGS. The ICARUS-T600 detector has collected 25 beam-associated events; the corresponding time of flight has been accurately evaluated, using all different time synchronization paths. The measured neutrino time of flight is compatible with the arrival of all events with speed equivalent to the one of light: the difference between the expected value based on the speed of light and the measured value is tof_c - tof_nu = (0.10 \pm 0.67stat. \pm 2.39syst.) ns. This result is in agreement with the value previously reported by the ICARUS collaboration, tof_c - tof_nu = (0.3 \pm 4.9stat. \pm 9.0syst.) ns, but with improved statistical and systematic errors.Comment: 21 pages, 13 figures, 1 tabl