Effects of Bisphenol A on Foxl2 gene expression and DNA damage in adult viviparous fish Goodeaatripinnis.

Bisphenol A (BPA) is an emerging pollutant of global concern. Viviparous fish Goodea atripinnis is endemic to the Central Mexican Plateau where BPA was detected; however, few studies examined the influence of this chemical on native viviparous fish. The effects of BPA (sublethal dose) were determined on DNA integrity and Foxl2 expression in G. atripinnis gonads, and interactions of BPA with FOXL2 protein. Genotoxicity analysis revealed that % comets, at 14 and 28 days and comet tail length (at 14 days) were significantly higher in exposed compared to controls. In general, the % DNA tail was not markedly higher in BPA-treated fish; however, tail moment related to tail length exhibited significant increases in DNA damage. RT-qPCR assays showed Foxl2 overexpression after 14 and 28 days of exposure in females; while in males, Foxl2 was overexpressed after 28 days. In silico analysis demonstrated that BPA interacted with seven residues located in FOXL2 homeodomain. In summary, sublethal BPA doses induced DNA damage and changes in Foxl2 expression in gonadal cells of G. atripinnis, which may adversely affect reproduction in BPA-exposed wild populations. Foxl2 overexpression and BPA-FOXL2 interaction suggested alterations in processes involving Foxl2. Viviparous fish may thus serve as potential non-conventional models for assessing pollutants effects.

Biological Responses of the American Coot (Fulica americana), in wetlands with contrasting environmental conditions (Basin of México).

Wetland ecosystems are subject to severe impacts (physical and chemical) and to the input of various xenobiotics that provoke toxicological consequences. Waterbirds are potential sentinel species of these environments. To analyze how habitat conditions affect the health of Fulica americana, early-warning biomarkers, histopathology, somatic indices, and water quality were examined in two wetlands of the Basin of Mexico: Xochimilco, an urban wetland highly eutrophic with a mixture of pollutants, and Tecocomulco (the reference site), a rural wetland with hunting migratory birds in winter, and with some agricultural contaminants. Coots were collected over 1 year, and the birds were aged, eviscerated, and weighed. Liver samples were analyzed biochemically and histologically. Biomarkers revealed that coots displayed higher lipid peroxidation and elevated activities of gamma-glutamyl transferase and alanine aminotransferase, suggesting hepatic damage during autumn and winter. In Tecocomulco, coots during winter has the highest thiobarbituric acid reactive substances (as a measure of oxidative stress), which may be associated with the presence of predators. In Tecocomulco, the higher gonadosomatic index was detected in spring and summer, while in Xochimilco it was elevated in summer, indicating a delayed egg laying and reproduction in coots from the latter study site. In both wetlands, leukocyte infiltration, alone or combined with vasocongestion, reflected alterations in the inflammatory processes in liver throughout the annual cycle and thus potentially altered hepatic function and organism survival. In both wetlands, coots were permanent residents and chronically exposed to different stressors, suggesting damage may be irreversible with potentially adversely reproductive consequences.

Liver histological changes and lipid peroxidation in the amphibian Ambystoma mexicanum induced by sediment elutriates from the Lake Xochimilco.

Lacustrine sediments accumulate pollutants that input from the lake watershed and can be released to the water column by sediment resuspension; thus, pollutants can change their bioavailability and exert adverse effects to aquatic biota. Shallow-urban lakes are particularly susceptible to receive pollutants from urban discharges and sediment resuspension. Lake Xochimilco, in Mexico City, an urban-shallow lake, faces multiple problems: urban sprawl, overexploitation of aquifers, drying of springs, discharge of wastewater from treatment plants, and sediment resuspension. The aquatic biota living in this ecosystem is continuously exposed to the release of pollutants from the sediments. We assessed the risk that pollutants released from sediments from Lake Xochimilco, Touristic (TZ) and Agriculture zone (AZ), can exert on a native amphibian species of the lake (Ambystoma mexicanum) through exposure bioassays to sediment elutriates. We evaluate alterations in the amphibian by three approaches: biochemical (level of lipid peroxidation, LPO), cellular (ultrastructure) and the liver histology of A. mexicanum and we compare them with a batch control. Additionally, we assessed heavy metals (Pb, Cd and Hg) in elutriates. Elutriates from TZ showed the highest concentrations of the metals assessed. Organisms exposed to sediment elutriates from either study sites showed higher LPO values than control organisms (p<0.05). Organisms exposed to elutriates from the TZ showed the most conspicuous damages: hepatic vasodilation of sinusoids, capillaries with erythrocytes, leukocyte infiltration and cytoplasmic vacuolation in hepatocytes. The biological responses assessed reflected the risk that faces A. mexicanum when is exposed for prolonged periods to sediment resuspension in Lake Xochimilco.

Toxicity induced by dieldrin and chlorpyrifos in the freshwater crayfish Cambarellus montezumae (Cambaridae).

The toxicity induced by insecticides in aquatic organisms is of utmost relevance because it may give a clue about the degree of health or damage of the involved ecosystem. In the present report, we determined the effect of dieldrin (DD) and chlorpyrifos (CP) on the freshwater crayfish, Cambarellus montezumae. The organisms (4-6 cm in diameter) were collected in the Ignacio Ramirez Reservoir, situated at 50 km Northeast of Mexico City, in the Rio Lerma Basin. Initially, we determined the LC50 value with the Probit method, then the DNA damage with single cell gel electrophoresis (comet assay applied at 24, 48, and 72 h of exposure) to the brain and hepatopancreas of animals exposed (in reconstituted water) to 0.05 and 0.5 microg/L of each insecticide. In the hepatopancreas of the same organisms, we determined the lipid peroxidation by applying the TBARS test. DNA damage and lipid peroxidation were also evaluated with the same methods to organisms exposed in water from the reservoir. In regard to the LC50, at 72 h of exposure, we found a value of 5.1 microg/L and a value of 5.62 microg/L for DD and CP, respectively. The comet assay applied at different exposure times showed significant DNA damage to both organs, with respect to the control level. In the case of DD, statistical significance was observed for the two doses in the whole evaluated schedule. CP was genotoxic in the brain with the high dose at 72 h, and in the hepatopancreas with the two tested doses at all evaluated exposure times. Also, a significant lipid peroxidation increase was detected with the two doses of insecticides. In the study with water from the reservoir, a more pronounced DNA damage was detected. Our results showed strong DNA damage induced by both insecticides in the crayfish, as well as a correlation with the lipid peroxidation effect, suggesting that oxidative stress is involved in the genotoxic alteration. Our results also showed the usefulness of the studied organism as well as the applied tests for the evaluation of toxicological effects, and suggested the pertinence of applying the comet assay to other freshwater organisms to evaluate the bioaccumulation of insecticides.

Assessing the health condition profile in the freshwater fish Astyanax aeneus in Champoton River, Mexico.

The use of biomarkers for monitoring aquatic environmental quality has gained considerable interest worldwide. The effects of the environmental conditions of Río Champotón, México, in the hotspot of Mesoamerica, were assessed in Astyanax aeneus, a native fish of the tropics of southwestern México. Pollution from agrochemical residues is a major problem in Río Champotón. Three study sites along the freshwater portion of the river were monitored in April, July, and November 2007 and February 2008. This study includes a water quality index, a set of biomarkers (hepatic glycogen levels and lipid peroxidation in liver, gills, and muscle) to assess the integrated biomarker response, and population bioindicators (gonadosomatic and hepatosomatic indices and Fulton's condition factor). Although the water quality index suggested low level of contamination in the Río Champotón, biomarkers indicated that A. aeneus is exposed to stressors that impair biological responses. The integrated biomarker response showed stress periods with higher biomarker response and recovery periods with decreasing biomarker values. The somatic indices did not indicate severe effects at the population level. This study illustrates the usefulness of lipid peroxidation evaluation in the assessment of aquatic health conditions and corroborates the suitability of A. aeneus as a sentinel species.

[Spatial and temporal variation patterns in aquatic macroinvertebrates of Tecocomulco Lake, Hidalgo (México)]. / Patrones de variación espacial y temporal de los macroinvertebrados acuáticos en la Laguna de Tecocomulco, Hidalgo (México).

Lake Tecocomulco, Hidalgo, is a relic of the ancient lakes ofAnahuac, important for the conservation of resident and migratory birds. However, the composition of aquatic macroinvertebrates is unknown; this is an important gap in conservation as they play an important role in the food web. This study analyzed the spatial and temporal variations in macroinvertebrate assemblages and their relationship with habitat characteristics. We carried out four monitoring campaigns covering the rainy and dry seasons. The monitoring was conducted at six study sites (four in the littoral zone and two in the middle part of the lake), environmental factors were recorded at each study site, water samples were collected for their physical and chemical analysis and aquatic macroinvertebrates were collected. A principal component analysis (PCA) was used to group study sites based on physical and chemical characteristics. Richness of taxa was analysed with rarefaction. We assessed the importance value index of each taxon (considering their frequency of occurrence and abundance). Similarity analyzes were performed between study sites and similarity of taxa with indices of Jaccard and Bray-Curtis, respectively. We performed a canonical correspondence analysis (CCA) between environmental factors and macroinvertebrate taxa. The PCA showed a marked seasonal variation represented by warm periods, with high values of conductivity, alkalinity, hardness, sulfates, and macronutrients (N and P) and the cold period with low values. We found a total of 26 taxa of aquatic macroinvertebrates and the highest richness was found in August. The Jaccard similarity analysis found differences between the littoral area and the limnetic zone, which differ also in the composition of macrophytes. The littoral zone had the highest taxa richness of macroinvertebrates and macrophytes, while the lowest diversity was found in the offshore zone. The CCA related physicochemical characteristics of the water body with macroinvertebrate taxa showing the influence of both physicochemical characteristics and the composition of macrophytes in the spatio-temporal patterns of aquatic macroinvertebrates in the lake. The dominance of Corixidae highlights a strong grazing activity in the lake and in turn suggests an important amount of food available for higher trophic levels. Our study shows that the macroinvertebrates of Tecocomulco Lake have spatial and seasonal variations that are related to both environmental and biotic factors with groups being dominant.

Health risk assessment by consumption of commercial biota contaminated with heavy metals in Tampamachoco coastal lagoon, Gulf of Mexico.

Metal pollution is a significant environmental and health problem in aquatic ecosystems worldwide, particularly in coastal systems impacted by emissions from thermoelectric plants, as is the case of the Tampamachoco lagoon. To evaluate the seasonal contamination levels of Cd, Pb, Cr, and Cu in species of commercial interest in the Tampamachoco lagoon and estimate the health risk associated with their consumption, a total of 180 fish, 90 oysters (Crassostrea virginica), 27 crabs (Callinectes sapidus), and 24 shrimp (Litopenaeus setiferus) were sampled. Metal concentrations in the species analyzed were Cu > Pb > Cr > Cd. According to the Target Hazard Quotient and the health risk index, consumption of the marine species examined should be considered safe for human health, as both values are <1. However, Carcinogenic risk values for Pb and Cr indicated that consumers may be at risk of cancer (10-3), due to exposure from the thermoelectric emissions.

Indigenous people doing citizen science to assess water quality using the BMWP in rivers of an arid semi-arid biosphere reserve in Mexico.

Arid and semi-arid areas are among the most threatened ecosystems on the planet. The Tehuacán-Cuicatlán Biosphere Reserve (TCBR), in southeastern Mexico, is an arid and semi-arid area with high biological diversity and human settlements of eight ethnic groups. Two rivers drain the reserve, Río Grande (RG) and Río Salado (RS), which are not subject to water quality monitoring by government agencies; however, measures of water quality of these rivers are needed to focus conservation actions on this resource. This work aimed to test the effectiveness of participatory water quality monitoring with the participation of three actors: Reserve management leaders, local communities, and academics, to monitoring water quality in the rivers of the TCBR. Ninety-two residents were trained to carry out water quality biomonitoring using the Biological Monitoring Working Party (BMWP) index calibrated for the reserve. The BMWP uses macroinvertebrate families to display numerical and categorical water quality scores. Additionally, the Water Quality Index (WQI) was assessed and the Normalized Difference Vegetation Index (NDVI) of the riparian zones was estimated in each study site. The mean WQI scores were 69.24 for RS (no treatment necessary for most crops and necessary treatment for public water supply) and 75.16 for RG (minor purification for crops requiring high-quality water and necessary treatment for public water supply). The BMWP showed five water quality categories (Excellent, Very Good, Good, Fair, and Poor), showing higher water quality scores in the upper portion of the basins and capable of discriminating study sites with lower scores close to human settlements. At one study site, data from participatory monitoring impelled actions taken to address a pollution source and influenced policy focus, reaching the maximum level of participatory-based monitoring. This led to avoid the discharge of wastewater into the river to conserve and protect the water resource. WQI is closely related to BMWP; however, the latter was far more sensitive to detecting areas affected by domestic water discharges. The NDVI presented low values for the TCBR, being lower in RS (the driest area). Although the NDVI showed a weak relationship with BMWP values, areas with higher NDVI values generally achieved higher BMWP values. The results of this study highlight the high sensitivity of the BMWP to detect several water quality conditions in the rivers running through the TCBR when compared to WQI. In addition, the usefulness of biomonitoring using the BMWP index was evident, as well as the importance of the participation of local inhabitants contributing to the knowledge of water quality in biosphere reserves and carrying out timely measures that allow the rivers in these reserves to be maintained in good condition.

Taming the terminological tempest in invasion science.

Standardised terminology in science is important for clarity of interpretation and communication. In invasion science - a dynamic and rapidly evolving discipline - the proliferation of technical terminology has lacked a standardised framework for its development. The result is a convoluted and inconsistent usage of terminology, with various discrepancies in descriptions of damage and interventions. A standardised framework is therefore needed for a clear, universally applicable, and consistent terminology to promote more effective communication across researchers, stakeholders, and policymakers. Inconsistencies in terminology stem from the exponential increase in scientific publications on the patterns and processes of biological invasions authored by experts from various disciplines and countries since the 1990s, as well as publications by legislators and policymakers focusing on practical applications, regulations, and management of resources. Aligning and standardising terminology across stakeholders remains a challenge in invasion science. Here, we review and evaluate the multiple terms used in invasion science (e.g. 'non-native', 'alien', 'invasive' or 'invader', 'exotic', 'non-indigenous', 'naturalised', 'pest') to propose a more simplified and standardised terminology. The streamlined framework we propose and translate into 28 other languages is based on the terms (i) 'non-native', denoting species transported beyond their natural biogeographic range, (ii) 'established non-native', i.e. those non-native species that have established self-sustaining populations in their new location(s) in the wild, and (iii) 'invasive non-native' - populations of established non-native species that have recently spread or are spreading rapidly in their invaded range actively or passively with or without human mediation. We also highlight the importance of conceptualising 'spread' for classifying invasiveness and 'impact' for management. Finally, we propose a protocol for classifying populations based on (i) dispersal mechanism, (ii) species origin, (iii) population status, and (iv) impact. Collectively and without introducing new terminology, the framework that we present aims to facilitate effective communication and collaboration in invasion science and management of non-native species.

Reproductive traits and population structure of Astyanax aeneus (Characiformes: Characidae) from a subtropical river in Mexico.

Champotón River is an unknown area within the Mesoamerican hotspot in Southestern México. Reproductive traits and population structure of Astyanax aeneus were analyzed along an environmental gradient of the upper, middle and lower sections of the river, where diverse environmental factors were recorded. For this, nets were cast for 1 h at each site and A. aeneus were collected from all sections with sweep nets (5 and 10 m long by 5 m deep, 0.03m mesh size) and a casting net (0.05m mesh size). At each study site and campaign, a total of 80 specimens (in average) were collected and were fixed in 10% formaldehyde for further analysis. Population structure by size was analyzed for each study site, based on the relative frequencies by standard length classes. The length-weight relationship was determined, and the identification of gonadal developmental stages, reproductive period, size at first sexual maturity, relative fecundity, sex ratio and somatic indexes (gonadosomatic, hepatosomatic and Fulton's condition factor) were also assessed. Seven size classes were found in the upper and middle sections, and nine downstream, with seasonal and spatial pattern in size-class frequency distribution. Size at first maturity was 45.7mm for females and 40.8mm for males. The maximum relative fecundity was recorded at the downstream site and was positively correlated with body weight and standard length. Sex ratio (1.8:1 males: females) differed significantly from expected values (1:1). Gonadosomatic index scores indicated that the reproductive period of this species in the Champot6n River was from April to July, during the warm and wet season. Hepatosomatic index was negatively correlated with the Gonadosomatic index, evidencing transfer of energy from the liver towards gamete production. This strategy enabled A. aeneus to maintain robustness during the study period with tiny changes in condition factor. A. aeneus in the Champotón River, as opposed to South American river congeneric species of similar size, shows early sexual maturity, a short reproductive period with high gonadosomatic index values, and high fecundity, a trade-off for the short reproductive period. Spatio-temporal segregation was evident: breeders congregate downstream, while juveniles prefer the upper reaches. This pattern allows A. aenus to be successful in a river with high frequency of hurricanes.

Oxidative stress in Physella acuta: An integrative response of exposure to water from two rivers of Atlantic Mexican slope.

Freshwater pollution is a complex mixture of xenobiotics due to the wastewater and the various chemicals routinely applied to agricultural lands that are discharged into water bodies. Xenobiotics can exert damage to the aquatic biota threatening the biodiversity of aquatic ecosystems. The oxidative damage and antioxidant responses have been widely investigated in freshwater organisms, mainly in fish and some invertebrates but in freshwater snails are scarce. This study aimed to assess the oxidative stress exerted by potential toxicity of water from two rivers of the Mexican Atlantic Slope (Tecolutla and Tuxpan rivers) in a freshwater mollusk Physella acuta. Lipid peroxidation level and a battery of antioxidant enzymes (Superoxide dismutase, Catalase and Glutathione peroxidase) were measured in P. acuta. The results are contextualized from an ecological point of view, associating the bioassay results with water quality characteristics. Water samples were obtained from three study sites for each river (in two seasons: Northern wind and dry). Twelve water quality variables were analyzed, and an additional water sample was used to perform a static bioassay for 96 h with snails grown in laboratory. After the exposure, we assessed lipid peroxidation level and the antioxidant responses of P. acuta exposed to water of rivers, and the Integrated Biomarker Response was computed. The highest lipid peroxidation level occurred in organisms exposed to water during the Northern wind season in both rivers. During this season, in the Tecolutla river, the superoxide dismutase activity was able to counteract the lipid peroxidation process, representing an adaptive response. In contrast, in the Tuxpan river, the superoxide dismutase was unable to counteract that process, stimulating CAT and GPx activities. The Integrated Biomarker Response showed that the Tecolutla river had higher values in the upper reaches than the Tuxpan river, showing a decreasing downstream gradient in both seasons. In the Tuxpan river, during the Dry season, the IBR score showed an increasing downstream gradient. During the Northern wind season, the IBR was higher in the upper reaches of both rivers, possibly due to the increased materials transported by runoff from the catchment, which includes a complex mixture of xenobiotics that affects the health of the sentinel species and aquatic biota in general. Based on our results, Physella acuta is proposed as sentinel species.

Atmospheric pollution assessment using polar graphs and its relationship with the bird community from the Sierra de Guadalupe, Mexico (initial data).

One of the most populated areas of the world is the Metropolitan Zone of the Mexican Valley, which has serious atmospheric pollution problems. To the north of the Metropolitan Zone is the Protected Natural Area Sierra de Guadalupe (PNASG), an area with a high diversity of birds, close to an industrial zone, and poor air quality (AQ). It is known that a poor AQ affects biodiversity. Therefore, this study aimed to evaluate the AQ using O3, CO, NO2, PM10 and PM2.5 polar graphics atmospheric pollutants (PGAP) and the Integrated Air Quality Index (IAQI) to examine its relationship with the structural diversity (SD) and the functional diversity (FD) of the bird community of the PNASG. In autumn-2019 and winter-2020, bird surveys and the PGAP with the pollutant concentrations were performed using data from Mexico City air quality network. The IAQI, SD and FD were estimated. Autumn-2019 registered the worst IAQI (334), the lowest wind speed (1.5 m/s), and the highest PGAP values (90). These worst AQ and the highest PGAP values were outside the PNASG but into a green urban area. This site also showed the highest SD scores (87), reflecting that the green urban areas function as a refuge for birds. The study sites with the best AQ (130.37), the lowest PGAP values (0.1) and the highest FD (0.7) were inside the PNASG. We conclude that a poor AQ minimizes the FD and that the PNASG is an essential buffer and a biological conservation area. The combined use of an integrated index of air quality with the polar graphics and diversity of birds (SD and FD) allow a better interpretation of air quality. It is necessary to establish mechanisms ensuring the conservation of the protected natural areas and green urban areas to improve air quality and biodiversity conservation.

Using different multivariate approaches to assess water quality of qanats in arid zones of Southern Central Mexico.

Qanats in the aquifer of the Tehuacán Valley (Mexico) represent an ancient way of using groundwater that is still practiced today. They are used mainly for agricultural irrigation. However, anthropogenic activities have jeopardized the use of these aquifers. We analyzed 24 qanats in the Tehuacán Valley to assess water quality. Based on 24 physicochemical variables, a water quality index (WQI) was constructed on a zero-to-100 scale, divided into five water quality classes. A decision-tree analysis was applied to identify the parameters with the highest influence on the WQI, considering the water quality classes as categorical responses and the values of physicochemical variables as drivers of these categories. We produced interpolation maps to identify trends. The relationship between the WQI and the normalized difference indices of vegetation and salinity (NDVI and NDSI, respectively) was analyzed using a ternary diagram. WQI scores showed that 12.5% of the qanats have very good quality; 25%, good quality; and the remaining (62.5%) range from moderate to unacceptable quality. The CHAID classification-tree method correctly explained 83.3% of the categories, with sulfates, alkalinity, conductivity, and nitrates as the main parameters that explain water quality. WQI was inversely related to NDVI and NDSI, showing seasonal differences. Interpolation maps suggest a better water quality in the northern zone of the aquifer.

Temporal distribution patterns of metals in water, sediment, and components of the trophic structure in a tropical coastal lagoon of the Gulf of Mexico.

Trophic transfer and bioaccumulation of trace metals have a profound impact on the structure and function of coastal areas; however, the metal accumulation patterns in detritus-based food webs and the influence of climatic variability have not been thoroughly investigated. The Tampamachoco Lagoon (Gulf of Mexico) is a coastal system impacted by emissions from a thermoelectric plant. We evaluated the spatial-temporal distribution patterns of Al, Cd, Hg, Cr, Cu, and Pb in water, sediments, and in organisms categorized by trophic levels (TLs), trophic guilds, and habitat preferences. The sediments had the highest concentrations of metals with no significant differences between seasons. The indices of geo-accumulation and potential ecological risk classified sediments as "moderately contaminated", evidencing a threat to human health through consumption of detritivores and filter-feeders. The lowest TLs (filter-feeders and detritivorous) reached the maximum Metal Pollution Index in the rainy season. According to discriminant analyses of metals and species, omnivorous and zoobentivorous organisms were associated with Hg during the rainy and dry seasons; while Al, Cd, and Cu were related to low TLs, and seston was associated with Pb. Food web magnification factor analysis showed that: (a) Pb, Cu, and Cr were biodiluted as trophic levels increased; (b) Cd and Hg showed temporal biomagnification trends; (c) Al, Pb, Cu, and Cd showed significant biodilution from the lowest TL to intermediate TLs; and (d) Hg was transferred from the lowest to intermediate TLs with clear biomagnification effects.

Aquatic macroinvertebrate assemblages in rivers influenced by mining activities.

Mining is one of the major pollution sources worldwide, causing huge disturbances to the environment. Industrial and artisanal mining activities are widespread in Mexico, a major global producer of various metals. This study aimed to assess the ecological impairments resulting from mining activities using aquatic macroinvertebrates assemblages (MA). A multiple co-inertia analysis was applied to determine the relationships between environmental factors, habitat quality, heavy metals, and aquatic macroinvertebrates in 15 study sites in two different seasons (dry and wet) along two rivers running across the Central Plateau of Mexico. The results revealed three contrasting environmental conditions associated with different MAs. High concentrations of heavy metals, nutrients, and salinity limit the presence of several families of seemingly sensitive macroinvertebrates. These factors were found to influence structural changes in MAs, showing that not only mining activities, but also agriculture and presence of villages in the basin, exert adverse effects on macroinvertebrate assemblages. Diversity indices showed that the lowest diversity matched both the most polluted and the most saline rivers. The rivers studied displayed high alkalinity and hardness levels, which can reduce the availability of metals and cause adverse effects on periphyton by inhibiting photosynthesis and damaging MAs. Aquatic biomonitoring in rivers, impacted by mining and other human activities, is critical for detecting the effect of metals and other pollutants to improve management and conservation strategies. This study supports the design of cost-effective and accurate water quality biomonitoring protocols in developing countries.

Historical analysis of an imperiled fish species: environmental variables modeling, biotic interactions, extirpation, and current restricted-range.

BACKGROUND: Analyses of spatial and temporal patterns and interactions are important for determining the abiotic factors limiting populations and the impact from other species and different anthropogenic stressors that promote the extirpation of species. The fish Hubbsina turneri de Buen (1940) was studied as a model species in a historical context at varying locations. Originally distributed only in the Lerma-Chapala basin, the main lake complex in Mexico, this species has not been collected from Lake Cuitzeo (LC) and now is restricted to Lake Zacapu (LZ). At present, the Highland splitfin is classified as critically endangered. METHODS: Historical information of LC and historical and current information from LZ were explored by applying cluster analysis and generalized additive mixed model (GAMM) to describe the biotic interactions among fish species and the relationship between density and environmental variables, respectively. The two lakes' contrasting abiotic/biotic characteristics provided elements to describe some species distribution limits in chemical ion gradients. Extirpation calendar dates were estimated using an optimal linear estimation method. Finally, a bibliographic review was conducted on the causes that promoted the extirpation and restriction of H. turneri and the prognosis for its reestablishment and conservation. RESULTS: Clusters showed the fishes relationship according to their distribution along the lakes. GAMM indicated that high H. turneri density is related to low hardness/fecal coliforms, medium depth/suspended solids, and high oxygen concentration. Estimated extirpation dates were between the years 2013 and 2018. The extirpation was linked to an abrupt drop in the LC volume, water quality degradation, increased biotic interactions within macrophytes habitats with native and introduced species, and fisheries bycatches. The current restricted range of H. turneri resulted from the draining of the larger lake, forcing the remaining populations to small spring-fed remnants. Recent samplings in LZ resulted in a low number of individuals. CONCLUSIONS: The integration of ecological interactions derived from statistical models, extirpation dates from nonparametric tests, and the exhaustive analysis of historical information can be applied to define the current situation of imperiled, ecologically relevant species, in different aquatic ecosystems. We are confident that this general framework is important for determining (1) the requirements and limitations of populations regarding abiotic variables, (2) biotic interactions (trophic and spatial) with native and introduced species, and (3) different anthropogenic stressors within and around the ecosystem. This knowledge will also allow understanding those aspects that contribute to the extirpation of populations and could help the restoration of the habitat and the reintroduction of extirpated species.

Effect of Yerbimat herbicide on lipid peroxidation, catalase activity, and histological damage in gills and liver of the freshwater fish Goodea atripinnis.

The use of herbicides for agricultural and aquatic weed control has increased worldwide. These substances are potentially toxic pollutants because they induce the production of reactive oxygen species for biological systems and exert oxidative stress in nontarget organisms living in the treated aquatic systems. Recent evidence suggests differences in the toxicity of glyphosate in the form of an active ingredient compared to the toxicity of glyphosate in combination with surfactants, such as those found in commercial formulations. In Mexico, one of the most widely used glyphosate-based herbicides is Yerbimat, which has agricultural as well as aquatic weed control applications. However, there are no aquatic toxicity data, particularly regarding native fish. Therefore, we determined the acute toxicity of commercial-formulation Yerbimat in a static bioassay at 96 h (LC(50)). We also determined its toxicity at 96 h in sublethal concentrations to assess the lipid peroxidation levels (LPX), catalase activity, hepatic glycogen content, and histological damage in the liver and gills of the fish Goodea atripinnis associated with chronic exposure (75 days). The LC(50) was 38.95 ± 0.33 mg/L. The results of the short-term exposure study indicate that Yerbimat can potentially induce oxidative stress in G. atripinnis, because LPX was increased in the gills and liver. Catalase activity was reduced in the gills but increased in the liver, whereas hepatic glycogen was depleted. Chronic exposure was associated with histopathological damage in the gills and liver, some of which was irreversible. Yerbimat represents a potential risk for aquatic biota; therefore, we recommend that its application be carefully considered.

Responses of antioxidant enzymes, lipid peroxidation, and Na+/K+-ATPase in liver of the fish Goodea atripinnis exposed to Lake Yuriria water.

Lake Yuriria, located in the heavily populated and polluted Mexican Central Plateau, receives domestic sewage, industrial effluents, and municipal wastewaters that are still directly discharged without treatment into the tributaries and the lake. Pollutants in water and sediments include heavy metals, aromatic hydrocarbons, and organochlorine pesticides. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), as well as Na⁺/K⁺-adenosine triphosphatase (Na⁺/K⁺-ATPase) activity, and lipid peroxidation (LPO) were evaluated in the livers of the fish Goodea atripinnis after 96 h of exposure to water collected in March and June 2005 from three sites: Y (limnetic zone), L (Lerma tributary), and C (la Cinta tributary). Physical and chemical parameters of the lake water were also analyzed. Increases in CAT activity and LPO levels at all three sites were detected compared with control fish (P < 0.05), while GPx and SOD activities decreased significantly (P < 0.05). Na⁺/K⁺-ATPase activities were similar to the control in fish exposed to limnetic water from both March and June but were higher than control at the two tributary sites in March (P < 0.05); fish exposed to water from the Lerma tributary in June exhibited lower Na⁺/K⁺-ATPase than the control (P < 0.05). During March, CAT and Na⁺/K⁺-ATPase activities were increasing more than in June in Y and L, respectively, while in June, SOD and GPx were depleted more than March in L and Y and L, respectively. Despite the antioxidant defenses of the fish liver, exposure to all water samples from Lake Yuriria exerted alterations in hepatic LPO levels, antioxidant enzymes, and Na⁺/K⁺-ATPase activities that could substantially impair the mechanisms of fish defenses against oxidative stress.

Helminths and lipid peroxidation in Astyanax aeneus (Pisces: Characidae) from a river in the humid subtropics of southeastern Mexico.

Xenobiotic mixtures in aquatic ecosystems may compromise fish health by inducing oxidative stress, decreasing resistance, and fostering susceptibility to pathogens such as helminths. Lipid peroxidation (LPO) is one of the most commonly used methods to evaluate oxidative stress. The present study examines the potential correlations between LPO in liver, muscle, and gill and the presence of helminths in Astyanax aeneus from a subtropical river in Mexico. Five helminth species were identified: the trematodes Uvulifer ambloplitis, a subdermal larval parasite, and Clinostomum complanatum, which infected the base of the gills; the nematodes Contracaecum sp. and Spiroxys sp.; and the acanthocephalan Polymorphus sp. The latter 3 species occurred in the posterior half of the intestine. Total helminth abundance was highest in April and July. Helminth species richness increased along a gradient from the headwaters to the middle reaches of the river. An integrated biomarker response for LPO (IBR-LPO) was assessed in the 3 tissues analyzed. IBR-LPO peaked in July. A direct correlation was found between gill and muscle LPO and mean abundance of Clinostomum complanatum, Contracaecum sp., and orthophosphate values, as well as between liver LPO and mean abundance of Polymorphus sp., whereas no relationship was found between LPO and U. ambloplitis or Spiroxys sp. This research revealed an association of both orthophosphate values and the presence or abundance of parasites with oxidative stress levels in A. aeneus, without any causal association, but rather as a result of synergistic processes associated with these variables.

Assessment of seasonal and spatial variations of biochemical markers in Corydalus sp. (Megaloptera: Corydalidae), a non-conventional biomonitor, in a mountain cloud forest in Mexico.

Rivers are critical ecosystems for protecting and harboring high biodiversity. Tropical rivers particularly are unique for facing extreme climatic events under the current accelerated disruption from human activities. The Bobos-Nautla river basin is exposed to climatic events and disturbances from anthropogenic impacts that stress aquatic organisms. We assessed the health condition of this river system using a non-conventional biomonitor, Corydalus sp., with a set of early-warning biomarkers including lipid peroxidation levels (LPO) and antioxidant activity, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and the neurotransmitter acetylcholinesterase (AChE) considering their spatial and temporal variations. Biomarkers and water quality parameters were analyzed, and the integrated biomarker response (IBR) was assessed as a stress index. Biomarkers showed no significant spatial differences; however, a high-stress period during the rainy season was detected, evidenced by the highest LPO levels; this period is related to the leaching of allochthonous materials from agricultural and urban zones. The peak IBR value during the rainy season confirmed the seasonality of biomarkers. A slight increase in IBR was recorded in lowlands, seemingly associated with agricultural land and human settlements. A principal component analysis showed nutrient enrichment during the rainy season and depletion during the cold-dry season, together with a peak activity of antioxidant enzymes. These results highlight the importance of climatic events such as the rainy season on the health condition of Corydalus sp., which is highly sensitive to the complex mixtures of pollutants that enter the waterbody during extreme climatic events, promoting oxidative stress. Our results also showed the ability of Corydalus sp. to recover and return to a basal level.