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We evaluated the multi-and transgenerational effects of single and combined environmentally relevant concentrations of glyphosate (GLY) and chlorpyrifos (CPF) in the estuarine rotifer Proales similis. The acute and chronic toxicities of GLY and CPF were determined as individual compounds and as a mixture. Rotifers were exposed to environmental concentrations of GLY (1, 10, 100, and 1000 μg/L) and CPF (0.1, 1, 5, and 10 μg/L). The main findings were as follows: (i) the LC

Chloroquine (CQ) has been widely used for many years against malaria and various viral diseases. Its important use and high potential to being persistent make it of particular concern for ecotoxicological studies. Here, we evaluated the toxicity of CQ alone and in combination with copper (Cu) to the euryhaline rotifer Proales similis. All experiments were carried out using chronic toxicity reproductive five‐day tests and an application factor (AF) of 0.05, 0.1, 0.3 and 0.5 by multiplying the 24-h LC50 values of CQ (4250 µg/L) and Cu (68 µg/L). The rate of population increase (r, d-1) ranged from 0.50 to 52 (controls); 0.19 to 0.39 (CQ); 0.09 to 0.42 (Cu); and -0.03 to 0.29 (CQ-Cu) and decreased significantly as the concentration of both chemicals in the medium increased. Almost all tested mixtures induced synergistic effects, mainly as the AF increased. We found that the presence of Cu intensifies the vulnerability of organisms to CQ and vice versa. These results stress the potential hazard that these combined chemicals may have on the aquatic systems. This research suggests that P. similis is sensitive to CQ as other standardized zooplankton species and may serve as a potential test species in the risk assessment of emerging pollutants in marine environments.

We identified and characterized microplastics (MPs) in the gastrointestinal tract (GT), gills (GI), and exoskeleton (EX) of Litopenaeus vannamei in a coastal lagoon from the SE Gulf of California. The most common MPs were fibers and fragments with an average size of 403 ± 296 μm, in which the transparent and blue colors predominated. The abundance (items/g as wet weight (ww)) in the GT, GI, and EX was 114.7 ± 33.2, 13.7 ± 5.3 and 3.0 ± 0.5, respectively. The abundance of MPs per shrimp was 13.3 ± 1.1, while the abundance per individual (ww) was 0.9 ± 0.2 MPs/g. Considering the consumption of shrimp in Mexico, MP abundance, and shrimp consumption (discarding GI and EX), we estimated MP ingestion as 280 items/person/year. The results from this study can be used as background information for future MP biomonitoring in shrimp species of ecological and commercial importance.

One contemporary issue is how environmental pollution and climate can affect the dissemination and severity of COVID-19 in humans. We documented the first case of association between particulate matter ≤2.5 μm (PM2.5) and COVID-19 mortality rates that involved rural and medium-sized municipalities in northwestern Mexico, where direct air quality monitoring is absent. Alternatively, anthropogenic PM2.5 emissions were used to estimate the PM2.5 exposure in each municipality using two scenarios: 1) considering the fraction derived from combustion of vehicle fuel; and 2) the one derived from modeled anthropogenic sources. This study provides insights to better understand and face future pandemics by examining the relation between PM2.5 pollution and COVID-19 mortality considering the population density and the wind speed. The main findings are: (i) municipalities with high PM2.5 emissions and high population density have a higher COVID-19 mortality rate; (ii) the exceptionally high COVID-19 mortality rates of the rural municipalities could be associated to dust events, which are common in these regions where soils without vegetation are dominant; and (iii) the influence of wind speed on COVID-19 mortality rate was evidenced only in municipalities with, Graphical abstract Image 1

Aquatic organisms that inhabit coastal environments are generally exposed to multiple mixtures of chemicals. The single and mixture toxicity of nine trace metals (As, Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn) to the rotifer Proales similis were examined at four different salinities (5, 15, 25, and 35 ppt). Chronic toxicity reproductive tests were performed using an application factor (AF) of 0.05, 0.1, 0.2, and 0.4 by multiplying the 24-h LC50 values of each metal. The metal mixture treatments were: T1, As–Cd–Cr–Cu–Fe–Hg–Ni–Pb–Zn; T2, As–Cd–Hg–Pb and; T3, Cr–Cu–Fe–Ni–Zn. The LC50 values ranged between 5 and 4140 μg L−1 in the following order: Hg > Cu > Fe > Pb > Cd > Zn > As > Cr > Ni in low salinity and Hg > Cu > Fe > Pb > Zn > As > Cd > Cr > Ni in high salinity conditions. In all cases, acute toxicity was higher at a salinity of 5 ppt compared to 35 ppt. Chronic toxicity tests indicated that single metal toxicity intensified as the AF increased and as salinity decreased. Regardless of salinity, Pb at 0.4 AF was the most toxic metal. Proales similis evidenced a higher growth in the As treatments (0.1 and 0.2 AF) at 35 ppt compared to controls. Furthemore, the T1 and T2 treatments were the most toxic, and in most cases, they induced a synergistic effect. Antagonism effects were detected in the T3 treatment at 25 and 35 ppt. The present data highlights the importance of the examination of pollution in natural environmental conditions in which many aquatic invertebrates endure.

One contemporary issue is how environmental pollution and climate can affect the dissemination and severity of COVID-19 in humans. We documented the first case of association between particulate matter ≤2.5 μm (PM2.5) and COVID-19 mortality rates that involved rural and medium-sized municipalities in northwestern Mexico, where direct air quality monitoring is absent. Alternatively, anthropogenic PM2.5 emissions were used to estimate the PM2.5 exposure in each municipality using two scenarios: 1) considering the fraction derived from combustion of vehicle fuel; and 2) the one derived from modeled anthropogenic sources. This study provides insights to better understand and face future pandemics by examining the relation between PM2.5 pollution and COVID-19 mortality considering the population density and the wind speed. The main findings are: (i) municipalities with high PM2.5 emissions and high population density have a higher COVID-19 mortality rate; (ii) the exceptionally high COVID-19 mortality rates of the rural municipalities could be associated to dust events, which are common in these regions where soils without vegetation are dominant; and (iii) the influence of wind speed on COVID-19 mortality rate was evidenced only in municipalities with

We isolated the rotifers Brachionus ibericus and Proales similis from the sediment of shrimp tanks and studied their individual demographic characters and competition between them at two food levels (0.25 × 106, 1.00 × 106 cells ml−1 of Nannochloropsis oculata at 25 °C) and salinities ranging from 10 to 30‰. Our hypothesis was that growth rates would be higher with increasing food levels and salinities. Observations were taken twice a day for life table studies and daily once for population growth experiments. Using survivorship and fecundity data, we derived various life history variables. Although the average life span (7.6 ± 0.4 days) and gross reproductive rate (33.8 ± 2.9 neonate female−1 day−1) of B. ibericus were higher than those of P. similis (average life span 5.4 ± 0.6 days and gross reproductive rate 13.0 ± 0.6 neonate female−1 day−1), the population growth experiments showed that P. similis had higher r values (0.32 ± 0.005 day−1) than B. ibericus (0.23 ± 0.002 day−1) at 1.0 × 106 cells ml−1 of N. oculata. The rotifer P. similis was more adversely affected due to the presence of B. ibericus than vice versa. The data are important for developing techniques for a large-scale culture of these rotifers as food in aquaculture.

Successful larval rearing of many fish species depends on the adequate selection of live food. Rotifers of the genus Brachionus are the most widely used in feeding protocols for freshwater and marine aquaculture. In this work, the utility of the euryhaline rotifer Proales similis as potential prey for the freshwater pike silverside Chirostoma estor estor larval rearing was investigated. The rotifers P. similis, Brachionus ibericus and B. plicatilis (body length: 84 ± 1.24, 193 ± 2.90 and 206 ± 4.20 μm, respectively) were used to evaluate C. estor estor larvae prey selectivity during the first 3 to 18 days post-hatching (DPH). Functional responses were tested at prey densities of 0.5, 1, 2, 4, 8 and 16 ind. mL−1. Larval survival was evaluated using four treatments: P. similis (T1), B. ibericus (T2), B. plicatilis (T3) and a mixed diet of all three taxa (T4). Results showed that P. similis was the C. estor estor most selected prey during the 3 to 7 DPH when compared to B. ibericus and B. plicatilis. From 8 to 18 DPH, the selectivity for P. similis shifted to increase selectivity for B. ibericus and B. plicatilis. At 4 to 12 DPH, functional responses indicated a greater P. similis consumption by larvae at high density (16 ind. mL−1). Larval survival was significantly higher in T1 than other treatments (T2 – T4). These findings provide evidence that P. similis can be included during the C. estor estor larval rearing. Proales similis could be therefore used at least during the 3 to 7 DPH, but the feeding protocols should be then complemented with brachionid rotifers. The present data are valuable for aquaculture practices and help approach the management and conservation issues of this endemic endangered fish species of the Central Plateau of Mexico.

Several abiotic factors influence the ecological responses of aquatic invertebrates to metal toxicity. We examined the effect of salinity (10, 20, and 30 psu) and temperature (25 and 32 °C) on acute and chronic arsenic (As) toxicity to the euryhaline rotifers, Proales similis and Brachionus ibericus. In general, higher salinities and low temperature resulted in lower arsenic toxicity. The population growth studies indicated that P. similis was more sensitive than B. ibericus to As. Arsenic toxicity intensified the vulnerability of P. similis to B. ibericus competition. Life table parameters decreased with increasing As levels in the medium. Chronic toxicity bioassays were more sensitive than acute toxicity tests for determining the adverse effect of As to rotifers. Our findings provide useful insights on the effect of arsenic on rotifer populations exposed to different temperature and salinity scenarios. Proales similis could be an important complement to brachionid rotifers for marine toxicity bioassays.

The demographic response of the brackish-water rotifers Proales similis and Brachionus plicatilis to mercury (0.5, 2, 8 and 32 μg L−1 of HgCl2) at different salinity levels (10 and 20‰) and two temperature (25 °C and 32 °C) regimes were evaluated. Median lethal concentration (LC50) for P. similis and B. plicatilis was 10 and 16 μg L−1, respectively, showing that Proales similis was more sensitive to mercury than B. plicatilis. The rate of population increase (r) for both species was greater at 10‰ salinity and 32 °C (ranged from 0.6 to 0.95 d−1). The r-value decreased as the concentration of mercury in the medium increased. Regardless of the temperature, at lower salinity and higher mercury concentration (32 μg L−1), P. similis died within six days. The survivorship of P. similis and B. plicatilis was higher at 25 °C than at 32 °C (ranged from 5 to 8 and 7–13 d, respectively). Fecundity was higher at 32 °C than at 25 °C for both rotifers species. There was a significant effect of the interaction among salinity, temperature, and mercury in both species on the reproductive variables such as net and gross reproductive rates, generation time and the rate of population increase. Considering the sensitivity of P. similis, we suggest that this species be included in the list of marine bioassay organisms.