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Abstract We study two-site deconstructions of the SU(2) L gauge group factor of the SM. Models based on this approach can explain the hierarchies of the quark masses and CKM mixing between third and light families if these fields are localised on different sites by the presence of hierarchical new physics scales. The model leads to an accidental global U(2) q × U(3) u × U(3) d flavour symmetry which prevents dangerously large effects in flavour observables, making a TeV extension of the SM possible. Given the structure of the PMNS matrix in the neutrino sector, we explore different possibilities for the arrangement of the leptons on the two sites, and consider different models with U(2) ℓ or U(3) ℓ flavour symmetries. The phenomenology of the models is mostly governed by a massive vector triplet of SU(2) L . We study the interesting interplay between LHC searches and precision observables. In particular, one of the models can give a sizeable lepton flavour universal effect in the Wilson coefficient C 9 while naturally suppressing contributions to C 10, as suggested by current b → sℓ + ℓ − data, predicting simultaneously a mild positive shift in the W boson mass.

Abstract Flavor deconstruction refers to ultraviolet completions of the Standard Model where the gauge group is split into multiple factors under which fermions transform non-universally. We propose a mechanism for charging same-family fermions into different factors of a deconstructed gauge theory in a way that gauge anomalies are avoided. The mechanism relies in the inclusion of a strongly-coupled sector, responsible of both anomaly cancellation and the breaking of the non-universal gauge symmetry. As an application, we propose different flavor deconstructions of the Standard Model that, instead of complete families, uniquely identify specific third-family fermions. All these deconstructions allow for a new physics scale that can be as low as few TeV and provide an excellent starting point for the explanation of the Standard Model flavor hierarchies.

Se analizó la distribución espacial de los principales peces continentales de España y su relación con variables tales como: altitud, orden de los ríos, pendiente, precipitaciones, temperaturas medias mínima y máxima, de invierno y verano respectivamente. Se consideraron las cuencas hidrográficas del Norte, Duero, Tajo, Ebro, Guadiana, Guadalquivir, Júcar, Segura, Sur e Internas de Cataluña. Las variables se analizaron bajo un enfoque espacial, utilizando un Sistema de Información Geográfica (SIG). Las asociaciones de las variables antes mencionadas, tanto cuantitativas como cualitativas, se determinaron aplicando un Análisis de Correspondencias Múltiples.

Abstract We present a model based on S 1 scalar leptoquarks to solve the tension observed in the recently proposed non-leptonic optimized observables L K ∗ K ¯ ∗ $$ {L}_{K^{\ast }{\overline{K}}^{\ast }} $$ and L K K ¯ $$ {L}_{K\overline{K}} $$ . These observables are constructed as ratios of U-spin related decays based on B d , s 0 → K ∗ 0 K ¯ ∗ 0 $$ {B}_{d,s}^0\to {K}^{\left(\ast \right)0}{\overline{K}}^{\left(\ast \right)0} $$ . The model gives a one-loop contribution to the Wilson coefficient of the chromomagnetic dipole operator needed to explain the tension in both non-leptonic observables, while naturally avoiding large contributions to the corresponding electromagnetic dipoles. The necessary chiral enhancement comes from an O(1) Yukawa coupling with a TeV-scale right-handed neutrino running in the loop. We endow the model with a U(2) flavor symmetry, necessary to protect light-family flavor observables that otherwise would be in tension. Furthermore, we show that the same S 1 scalar leptoquark is capable of simultaneously explaining the hints of lepton flavor universality violation observed in charged-current B-decays. The model therefore provides a potential link between two puzzles in B-physics and TeV-scale neutrino mass generation. Finally, the combined explanation of the B-physics puzzles unavoidably results in an enhancement of B B → Kν ν ¯ $$ \mathcal{B}\left(B\to K\nu \overline{\nu}\right) $$ , yielding a value close to present bounds.

Abstract The Minimal Linear $$\sigma $$ σ Model is a useful theoretical laboratory. One can investigate in a perturbative renormalisable model the properties of the Higgs boson as a pseudo-Goldstone boson, the phenomenological effects of the radial mode of the field $$\texttt {s}$$ s which spontaneously breaks the global SO(5) symmetry and the validity of conclusions based on the Effective Field Theory approach with the field $$\texttt {s}$$ s in the spectrum, after the decoupling of heavy degrees of freedom. In this paper all those issues are discussed in the framework of the Minimal Linear $$\sigma $$ σ Model with CP violating phases leading to pseudoscalar components in the effective Standard Model Yukawa couplings. Also the character of the electroweak phase transition in the presence of the field $$\texttt {s}$$ s is investigated.

1.During 2001 and 2002, 12 tributaries of the River Duero basin, north-west Spain, were sampled. Pearl mussels Margaritifera margaritifera (L.) were located in two of them. Isolated individuals were found in the River Tera, a tributary of the River Esla; and only a few colonies with more than 20 mussels were found in the River Negro.2.All of the specimens found were adults (mean length 95 mm), with juveniles being absent in the river bed. The River Negro plots showed a low median mussel density (0.11 m-2), and that of greatest size consisted of 164 ageing individuals.3.Mussels were mainly located in permanent rivers and in shallow stretches with little flow of water, with heterogeneous substrates and heavily shaded by the riparian woods. The whole basin has well-conserved rivers with cold oligotrophic water and poor mineralization due to the insolubility of the rocks.4.This relic population has a severely restricted distribution because of a series of large reservoirs in a hydropower complex of the rivers Duero and Esla (caused by the construction of the Ricobayo Dam in 1947) and their negative impact on the rheophilous fish. The mussels of the River Tera have been isolated from the rest of the Duero basin since 1969 (Cernadilla Dam), whereas in the River Negro they have been isolated since 1995 (Agavanzal Dam). Copyright 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The recent B-meson anomalies are coherently explained at the TeV scale by 4321 gauge models with hierarchical couplings reminiscent of the Standard Model Yukawas. We show that such models arise as the low-energy limit of a complete theory of flavor, based on a warped fifth dimension where each Standard Model family is quasi-localized on a different brane. The Higgs is identified as a pseudo-Nambu-Goldstone boson emerging from the same dynamics responsible for 4321 symmetry breaking. This novel construction unifies quarks and leptons in a flavor non-universal manner, provides a natural description of flavor hierarchies, and addresses the electroweak hierarchy problem.

Aggregated mobility indices (AMIs) derived from information and communications technologies have recently emerged as a new data source for transport planners, with particular value during periods of major disturbances or when other sources of mobility data are scarce. Particularly, indices estimated on the aggregate user concentration in public transport (PT) hubs based on GPS of smartphones, or the number of PT navigation queries in smartphone applications have been used as proxies for the temporal changes in PT aggregate demand levels. Despite the popularity of these indices, it remains largely untested whether they can provide a reasonable characterisation of actual PT ridership changes. This study aims to address this research gap by investigating the reliability of using AMIs for inferring PT ridership changes by offering the first rigorous benchmarking between them and ridership data derived from smart card validations and tickets. For the comparison, we use monthly and daily ridership data from 12 cities worldwide and two AMIs shared globally by Google and Apple during periods of major change in 2020-22. We also explore the complementary role of AMIs on traditional ridership data. The comparative analysis revealed that the index based on human mobility (Google) exhibited a notable alignment with the trends reported by ridership data and performed better than the one based on PT queries (Apple). Our results differ from previous studies by showing that AMIs performed considerably better for similar periods. This finding highlights the huge relevance of dealing with methodological differences in datasets before comparing. Moreover, we demonstrated that AMIs can also complement data from smart card records when ticketing is missing or of doubtful quality. The outcomes of this study are particularly relevant for cities of developing countries, which usually have limited data to analyse their PT ridership, and AMIs may offer an attractive alternative., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright: © 2024 Lizana et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Normally the social approaches addressed in public housing policies are unclear in the implementation processes. Indeed, public agencies do not have systems that integrate clear social criteria to consider the social assessment of public housing projects. Therefore, the inclusion of social sustainability in planning and early decision-making is limited. In addition, social development technically involves variables that are not normally independent, and its completeness means their relationships must be considered to sum up the impacts. Thus, this work proposes a structural model that explains an integral interrelation of social criteria that determines socially sustainable housing projects for the vulnerable population in Chile. For this, a theoretical model was constructed and validated using a structural equation model (SEM). This system derives from the application of a survey applied to 188 professionals related to the development of public housing. From this, a model of social sustainability of public housing is validated with ten social criteria and eleven unidirectional interrelations, structured in two dimensions: the functional conditions of the home and the environmental conditions of the house. In the first dimension, the relation between the Improvement in family economic availability and Spaces for family development stands out. In the second, the strongest link is between Community health and safety and the Integration of the design in the context.

Recent advances in ultrasonography (US) technology established modalities, such as Doppler-US, HistoScanning, contrast-enhanced ultrasonography (CEUS), elastography, and micro-ultrasound. The early results of these US modalities have been promising, although there are limitations including the need for specialized equipment, inconsistent results, lack of standardizations, and external validation. In this review, we identified studies evaluating multiparametric ultrasonography (mpUS), the combination of multiple US modalities, for prostate cancer (PCa) diagnosis. In the past 5 years, a growing number of studies have shown that use of mpUS resulted in high PCa and clinically significant prostate cancer (CSPCa) detection performance using radical prostatectomy histology as the reference standard. Recent studies have demonstrated the role mpUS in improving detection of CSPCa and guidance for prostate biopsy and therapy. Furthermore, some aspects including lower costs, real-time imaging, applicability for some patients who have contraindication for magnetic resonance imaging (MRI) and availability in the office setting are clear advantages of mpUS. Interobserver agreement of mpUS was overall low; however, this limitation can be improved using standardized and objective evaluation systems such as the machine learning model. Whether mpUS outperforms MRI is unclear. Multicenter randomized controlled trials directly comparing mpUS and multiparametric MRI are warranted., Competing Interests: The authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: A.L.A. is the consulting physician for Koelis., (© The Author(s), 2022.)

Cowper's gland syringocele (CGS) is the cystic dilation of its duct. It is an uncommon urological condition and is thought to be more commonly encountered in pediatric urology. However, it is in adults that CGS poses a diagnostic challenge because of its "chameleon-like" clinical presentation that may masquerade multiple urological etiologies. In this population, where urological conditions are more prevalent, CGS may present as bladder outlet obstruction, recurrent urinary tract infections, gross hematuria, urinary retention, perineal pain, or abscess., (© 2022 The Authors.)

Complete testicular epididymal dissociations are exceedingly rare conditions where the epididymis and the vas deferens are completely dissociated from the testicle. We present the case of a 46-year-old male with a history of chronic, intermittent and severe left testicular pain who was found to have a complete testicular epididymal dissociation at the time of surgical exploration and bilateral orchidopexy. Microsurgical approximation of the tail of the epididymis to the tunica albuginea of the testis with reapproximating the muscularis of the spermatic cord to the epididymal appendage was performed with subsequent relief of symptoms., Competing Interests: This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors., (© 2022 Published by Elsevier Inc.)

Alterations in microRNA (miRNA) profiles, induced by tumor microenvironment stressors, like hypoxia, allow cancer cells to acquire immune-resistance phenotypes. Indeed, hypoxia-induced miRNAs have been implicated in cancer progression through numerous cancer cell non-autonomous mechanisms, including the direct transfer of hypoxia-responsive miRNA from cancer to immune cells via extracellular vesicles. Connexin-43 (Cx43)-constituted gap junctions (GJs) have also been involved in miRNA intercellular mobilization, in other biological processes. In this report, we aimed to evaluate the involvement of Cx43-GJs in the shift of miRNAs induced by hypoxia, from hypoxic melanoma cells to dendritic cells and melanoma-specific cytotoxic T lymphocytes (CTLs). Using qRT-PCR arrays, we identified that miR-192-5p was strongly induced in hypoxic melanoma cells. Immune cells acquired this miRNA after co-culture with hypoxic melanoma cells. The transfer of miR-192-5p was inhibited when hypoxic melanoma cells expressed a dominant negative Cx43 mutant or when Cx43 expression was silenced using specific short-hairpin RNAs. Interestingly, miR-192-5p levels on CTLs after co-culture with hypoxic melanoma cells were inversely correlated with the cytotoxic activity of T cells and with ZEB2 mRNA expression, a validated immune-related target of miR-192-5p, which is also observed in vivo. Altogether, our data suggest that hypoxic melanoma cells may suppress CTLs cytotoxic activity by transferring hypoxia-induced miR-192-5p through a Cx43-GJs driven mechanism, constituting a resistance strategy for immunological tumor escape.

Introduction and Aim: Suicide and harmful alcohol consumption are major health problems, especially in medical students. This study aimed to evaluate the association between risk for alcohol abuse and suicide risk in medical interns of Peruvian hospitals., Design and Methods: We conducted a multicentre cross-sectional study in medical interns from 18 Peruvian hospitals. We measured suicide risk, risk for alcohol abuse, depression and self-esteem using the Plutchik Suicide Risk Scale, CAGE, Zung Self-Rating Depression Scale and Rosenberg Self-Esteem Scale, respectively. We used χ 2 and Student t-tests for descriptive analysis. To evaluate the association between risk for alcohol abuse and suicide risk we generated crude and adjusted Poisson regression models with robust variance and estimated prevalence ratios with 95% confidence intervals., Results: We surveyed 433 medical interns. The prevalence of suicide risk and risk for alcohol abuse was 19.6% and 27.5%, respectively. We found significant differences in suicide risk according to age (P < 0.001), region of origin (P = 0.002), with whom the participant lived (P < 0.001), university of origin (P = 0.040), type of hospital (P = 0.042), family history of attempted suicide (P = 0.043), self-esteem level (P < 0.001) and alcohol consumption (P < 0.001). In the adjusted model, age (PRa: 1.11, 95% confidence interval 1.05-1.17) and risk for alcohol abuse (PRa: 7.60, 95% confidence interval 4.46-12, 96) were associated with suicide risk., Discussion and Conclusions: Two out of 10 medical interns had a positive screening for suicide risk. Age and especially risk for alcohol abuse were the associated variables., (© 2019 Australasian Professional Society on Alcohol and other Drugs.)

Since domestication, a large number of livestock breeds adapted to local conditions have been created by natural and artificial selection, representing one of the most powerful ways in which human groups have constructed niches to meet their need. Although many authors have described local breeds as the result of culturally and environmentally mediated processes, this study, located in mainland Spain, is the first aimed at identifying and quantifying the environmental and human contributions to the spatial structure of local breed diversity, which we refer to as livestock niche. We found that the more similar two provinces were in terms of human population, ecological characteristics, historical ties, and geographic distance, the more similar the composition of local breeds in their territories. Isolation by human population distance showed the strongest effect, followed by isolation by the environment, thus supporting the view of livestock niche as a socio-cultural product adapted to the local environment, in whose construction humans make good use of their ecological and cultural inheritances. These findings provide a useful framework to understand and to envisage the effects of climate change and globalization on local breeds and their livestock niches.

Agriculture-related pollution is among the major causes of global amphibian population declines. The multiple stressors to which amphibians are exposed in the field, such as predation pressure, can make agrochemicals far more deadly than when they act in isolation. Even within a small area, diffuse agricultural pollution does not affect all aquatic environments equally, which could account for local differences in amphibian sensitivity to agrochemicals. We examined the combined effects of ammonium nitrate fertilizer (0 to 45.2 mg N-NH 4(+)/L) and predator stress on larval Western spadefoot toad (Pelobates cultripes), using adult caged male marbled newts (Triturus marmoratus) as predators. We compared the interaction between both stressors in tadpoles from two ponds separated by 3 km. No significant mortality was observed (survival > 80% in all cases). Local differences were detected when analyzing larval growth, with a significant interaction between factors for one of the two populations tested (Fornillos de Fermoselle). Although tadpoles exposed to 45.2 mg N-NH 4(+)/L were 7% smaller than controls, the presence of predators from a foreign community resulted in animals 15% larger than those raised without predators after 15 d of experiment. Interestingly, predators from the same community as the tadpoles did not affect larval growth. The length of the tadpoles from a nearby location (Mámoles) was unaffected after exposure to ammonium nitrate and predatory stress., (Copyright © 2011 SETAC.)

The mean age of a population of agile frogs (Rana dalmatina) from the Iberian Peninsula was estimated using mark and recapture and skeletochronology. Life-history parameters, including growth rate, body length, age and size at maturity, sexual dimorphism and longevity, were studied. The regression between age and snout-vent length (SVL) was highly significant in both sexes. Males reached sexual maturity at two years of age, although sometimes they can reach it at only one year of age. The average SVL at maturity was 51.75 mm (standard error (SE)=0.71; n=45). Females reached sexual maturity at two years of age with an average SVL of 62.14 mm (SE=2.20; n=14). A subset of the female population reached sexual maturity at three years of age. Growth was rapid until sexual maturity was reached. There was an overlap of SVL between different age classes. Growth was continuous, fulfilling the conditions of Von Bertalanffy's model. The growth coefficient (K) was 0.840 in males and 0.625 in females. The maximum SVL was greater in females (73.00 mm) than in males (59.50mm). Sexual dimorphism was significantly biased towards females in all age classes. The maximum longevity observed was 6 years in females and 8 years in males. Management strategies for agile frogs should take into account factors such as these life-history characteristics., (Copyright © 2011 Elsevier GmbH. All rights reserved.)

Pollution from agrochemicals may be contributing to the global decline of amphibian populations. Environmentally relevant concentrations of a fertiliser, ammonium nitrate, and a commercial formulation of the herbicide glyphosate Roundup Plus were tested on the embryonic development of Chioglossa lusitanica. This study introduces new data at three different levels. First, we provide previously unknown information about hatchling traits of C. lusitanica. Second, we present the first ecotoxicological study of this endangered species, to which environmental pollution is considered a major threat. Third, we conduct the first experiment with an amphibian species exposed to a mixture of a glyphosate-based herbicide and a nitrogenous fertiliser. Control individuals hatched with an average (±SD) total length of 18.77 (±2.02) mm and at an average Harrison's developmental stage of 44.58 (±1.24). Mean hatching time among controls was 11.52 (±1.29) weeks. None of the chemicals or their interaction produced lethal effects; however, a significant interaction was found when analysing total length at hatching. Individuals exposed to the herbicide hatched at a larger size than controls, and this effect was especially clear when the fertiliser was added to the water. The absence of pollutant-related mortality or severe sublethal effects is in agreement with most studies indicating a high tolerance of amphibian embryos to agrochemicals. However, further research considering other life stages and additional natural factors (i.e., predators, food availability) is needed to estimate the ecological impact of chemical mixtures on C. lusitanica.

Many amphibians are known to suffer embryonic die-offs as a consequence of Saprolegnia infections; however, little is known about the action mechanisms of Saprolegnia and the host-pathogen relationships. In this study, we have isolated and characterized the species of Saprolegnia responsible for infections of embryos of natterjack toad (Bufo calamita) and Western spadefoot toad (Pelobates cultripes) in mountainous areas of Central Spain. We also assessed the influence of the developmental stage within the embryonic period on the susceptibility to the Saprolegnia species identified. Only one strain of Saprolegnia was isolated from B. calamita and identified as S. diclina. For P. cultripes, both S. diclina and S. ferax were identified. Healthy embryos of both amphibian species suffered increased mortality rates when exposed to the Saprolegnia strains isolated from individuals of the same population. Embryonic developmental stage was crucial in determining the sensitivity of embryos to Saprolegnia infection. The mortalities of P. cultripes and B. calamita embryos exposed at Gosner stages 15 (rotation) and 19 (heart beating) were almost total 72 h after challenge with Saprolegnia, while those exposed at stage 12 (late gastrula) showed no significant effects at that time. This is the first study to demonstrate the role of embryonic development on the sensitivity of amphibians to Saprolegnia.

This article documents the addition of 396 microsatellite marker loci to the Molecular Ecology Resources Database. Loci were developed for the following species: Anthocidaris crassispina, Aphis glycines, Argyrosomus regius, Astrocaryum sciophilum, Dasypus novemcinctus, Delomys sublineatus, Dermatemys mawii, Fundulus heteroclitus, Homalaspis plana, Jumellea rossii, Khaya senegalensis, Mugil cephalus, Neoceratitis cyanescens, Phalacrocorax aristotelis, Phytophthora infestans, Piper cordulatum, Pterocarpus indicus, Rana dalmatina, Rosa pulverulenta, Saxifraga oppositifolia, Scomber colias, Semecarpus kathalekanensis, Stichopus monotuberculatus, Striga hermonthica, Tarentola boettgeri and Thermophis baileyi. These loci were cross-tested on the following species: Aphis gossypii, Sooretamys angouya, Euryoryzomys russatus, Fundulus notatus, Fundulus olivaceus, Fundulus catenatus, Fundulus majalis, Jumellea fragrans, Jumellea triquetra Jumellea recta, Jumellea stenophylla, Liza richardsonii, Piper marginatum, Piper aequale, Piper darienensis, Piper dilatatum, Rana temporaria, Rana iberica, Rana pyrenaica, Semecarpus anacardium, Semecarpus auriculata, Semecarpus travancorica, Spondias acuminata, Holigarna grahamii, Holigarna beddomii, Mangifera indica, Anacardium occidentale, Tarentola delalandii, Tarentola caboverdianus and Thermophis zhaoermii., (© 2010 Blackwell Publishing Ltd.)

Sublethal effects of toxicants can upset normal behavioural responses to predators, leading to increased predation. For example, sensory capabilities can be impaired by toxicants, leading to difficulty in detecting predators or other threats. Alteration of locomotor abilities by pollutants can also explain the difficulty of tadpoles to escape from predators. Here we assess the effects of a nitrogenous fertilizer on the response to predators shown by anuran tadpoles. In a first experiment, we chronically exposed Iberian painted frog (Discoglossus galganoi) and spadefoot toad (Pelobates cultripes) tadpoles to environmentally relevant concentrations of ammonium nitrate. After the exposure, we tested tadpoles' ability to avoid predation by the red crayfish (Procambarus clarkii). In a second experiment, we analysed the escape behaviour of P. cultripes tadpoles as a function of ammonium nitrate exposure and presence of predatory crayfishes. Tadpoles of both species that were exposed to ammonium nitrate were consumed by crayfishes faster than controls (mean time of predation: Dg controls=18.03 h, 90.3 mg N-NO(3)NH(4)/L=7.48 h; Pc controls=16.12h, 90.3 mg N-NO(3)NH(4)/L=9.46 h). Control larval P. cultripes showed specific anti-predator escape responses, whereas those exposed to the fertilizer did not. We demonstrate, for the first time in amphibians, how nitrogenous fertilizers can affect larval defensive behaviours, and thereby increase the risk of predation. Our results emphasize the importance of considering environmental stresses on the ecotoxicological studies with amphibians., ((c) 2010 Elsevier B.V. All rights reserved.)

The negative effects of pollution on amphibians are especially high when animals are additionally stressed by other environmental factors such as water salinity. However, the stress provoked by salinity may vary among populations because of adaptation processes. We tested the combined effect of a common fertilizer, ammonium nitrate (0-90.3 mg N-NO3NH4/L), and water salinity (0-2 per thousand) on embryos of two Pelophylax perezi populations from ponds with different salinity concentrations. Embryos exposed to the fertilizer were up to 17% smaller than controls. Survival rates of embryos exposed to a single stressor were always below 10%. The exposure to both stressors concurrently increased mortality rate (>95%) of embryos from freshwater. Since the fertilizer was lethal only when individuals were stressed by the salinity, it did not cause lethal effects on embryos naturally adapted to saline environments. Our results underscore the importance of testing multiple stressors when analyzing amphibian sensitivity to environmental pollution., (Copyright (c) 2009 Elsevier Ltd. All rights reserved.)

Although many studies have assessed the effects of water pollution on amphibians, few have focused on the alteration of vital behaviors. Newt species usually display complex courtship behavior that may be altered by sublethal levels of contaminants. We analyzed the effects of ammonium nitrate and water acidification on courtship behavior of the Iberian newt (Lissotriton boscai). We exposed newt couples to three treatments (control, nominal 90 mg N--NO3NH4/L, and nominal pH 4) and recorded the occurrence of each of the three courtship phases (orientation, static display, and spermatophore transfer) as well as the latency to initiate courtship, overall courtship time, male perseverance, and female responsiveness. Major effects were observed in the acid treatment. Low pH inhibited orientation. None of the control couples failed to court, whereas 17% of couples from the low-pH treatment did not perform any courtship movement. Latency to initiate courting was twice as high in couples exposed to acidification as in controls. Low pH also affected the overall time of courtship and perseverance time of males in unsuccessful encounters. Ammonium nitrate did not cause any significant effect. Only the female response index and the duration of the tail-fanning movement (the major display during L. boscai courtship) were slightly reduced by the fertilizer. We report a pollution-mediated alteration of courtship behavior, to our knowledge for the first time, in amphibians. This kind of sublethal effect should be considered when estimating potential impacts of water pollution on natural populations.

Many amphibians are known to suffer embryonic die-offs as a consequence of an emergent disease known as 'Saprolegnia infections'. Thus far, the only species of Saprolegnia shown to be involved in natural infections is Saprolegnia ferax. In this study, we have isolated and characterized another Saprolegnia species responsible for 'Saprolegnia infections' on embryos of Bufo calamita in mountainous areas of central Spain. The strain was identified as belonging to Saprolegnia diclina based on morphological, physiological and molecular characters (sequencing of the internal transcribed region of ribosomal DNA). Zoospores of the new strain were able to infect embryos of Bufo calamita, and the symptoms observed were the same as those observed in natural infections. The results presented emphasize the need to carry out isolations and characterizations of the species and/or strains involved in this emergent disease. This will be important in order to design strategies to prevent the impact and spread of species (or strains) pathogenic to amphibians.

Embryonic mortality in many aquatic animals, including most amphibian species, is usually very high. In addition to mechanical and chemical defences, some species have developed behavioural patterns that can increase egg survival. For example, females of some newt species protect their eggs by wrapping them in leaves of aquatic plants. We have studied the effects of ammonium nitrate (nominal concentration of 90.3 mg N-NO(3)NH(4)/L) and water acidification (pH 4-5) on egg wrapping behaviour of the dwarf newt, Triturus pygmaeus, and on whether this specific behaviour may protect embryos from contamination. Although either ammonium nitrate or low pH did not inhibit oviposition, the mean percentage of eggs that were wrapped by the females was significantly lower at low pH than in controls. In order to assess the potential effects of oviposition behaviour on embryonic survival, we exposed simultaneously wrapped and unwrapped eggs to ammonium nitrate and acid pH during their development. After 25 days of exposure, ammonium nitrate reduced length and developmental stage at eclosion of the exposed individuals, regardless of whether they were wrapped or unwrapped. The fertilizer caused a significantly higher mortality in unwrapped than wrapped eggs. The potential impact of water pollution on amphibians in the field may include not only direct effects on embryonic and larval survival but also alteration of breeding behaviours, which may reduce reproductive success and ultimately affect population's condition.

In static renewal experiments, we studied how developmental stage influences the effect of ammonium nitrate on embryonic and larval stages of anuran amphibians. The observed lethal effects caused by ammonium nitrate increased with both concentration and duration of exposure. Significant differences were observed in sensitivity to ammonium nitrate as a function of developmental stage in Discoglossus galganoi, Pelobates cultripes, and Bufo calamita. In D. galganoi and P. cultripes, younger individuals displayed greater acute effects from the chemical fertilizer compared with older individuals. For example, 100% of P. cultripes hatchlings died after 4 d of exposure to a nominal concentration of 225.8 mg N-NO3NH4/L, whereas less than 40% of individuals from older larval stages died when exposed to this concentration. A delay of 4 d in the beginning of the exposure to the chemical was enough to cause significant differences in sensitivity. Bufo calamita showed a higher sensitivity in later larval stages after 12 d of exposure. Hyla meridionalis and B. calamita were less sensitive than the other two species. Peak ammonium nitrate concentrations usually occur when amphibians are breeding and, thus, when the most sensitive aquatic stage is in the water. The developmental stage of the test animals should be considered when evaluating the risk of ammonium nitrate to amphibians.

We conducted static experiments to assess the effects of ammonium nitrate fertilizer on embryos and larvae of six European amphibians: sharp-ribbed salamander (Pleurodeles waltl), Iberian painted frog (Discoglossus galganoi), western spadefoot toad (Pelobates cultripes), common toad (Bufo bufo), natterjack toad (Bufo calamita), and common tree frog (Hyla arborea). Embryos were exposed to different and environmentally relevant concentrations of ammonium nitrate (0 to 200 mg NO(3)(-)/L) for 15 days. Hatching took place during the experiments. H. arborea was extremely sensitive and had high mortality after 8 days of exposure even at the lower fertilizer levels. D. galganoi and B. bufo were also very sensitive and had significant mortality after 15 days of exposure. The rest of the species did not suffer lethal effects but suffered abnormalities or decreased growth at the highest fertilizer concentrations. Chemical fertilizers or manure could have contributed to the observed decrease of B. bufo and D. galganoi in agricultural areas of the Iberian Peninsula during recent years. H. arborea was the most sensitive species studied. The results of our study showed that environmentally relevant levels of ammonium nitrate can induce mortality and might affect population dynamics of this species in agricultural environments.

In the present paper we make a bifurcation analysis of an SIRS epidemiological model depending on all parameters. In particular we are interested in codimension-2 bifurcations.