Extreme variation in the reproductive phenology of the weed Ruellia nudiflora

Temporal variation in morphological and life‐history traits is directly linked to phenotypic plasticity in perennial plants. Phenotypic plasticity in reproductive phenology determines colonisation ability and population persistence in invasive weeds. We describe the reproductive phenology of Ruellia nudiflora (a cleistogamous weed) and assess the plasticity of its response to between‐year environmental variation in two contrasting light environments. We recorded the flower and fruit production of focal plants under two experimental levels of light intensity (open vs. shaded) over two years. Our results suggest that light differentially affects the phenology of reproductive structures, but not between‐year variation. Specifically, individual production of chasmogamous structures (flowers and fruit) ended earlier under shaded conditions than in the open, whilst production of cleistogamous fruits was not affected. At the population level, there was between‐year variation in the phenology of chasmogamous structures, which were bimodal and unimodal in the first and second year respectively. At the individual level, we found very low repeatability, suggesting high levels of phenotypic plasticity. Temporal variation in rainfall did not explain phenological variation. Although shade did not affect between‐year variation, it produced a briefer period of production of chasmogamous structures. This effect of shade may have some consequences for the genetic background of R. nudiflora's progeny, because only chasmogamous flowers can be out‐crossed, and this therefore might be an important factor to consider when designing management strategies.     

Some aspects of the environmental exposure to chromium residues in Mexico

Research was conducted to determine the environmental effects of Cr residues from a chromite-ore processing plant (Cromatos de México) on the human population living in the surrounding area. The results of this study provided the first quantitative evidence of the transfer of Cr to the atmosphere, soil and subsequently to ground water. The atmospheric concentration of Cr ranged from 0.25 to 0.39 μg m^?3, seven times higher than the level found in the control area. Most of the well water samples (90%) had a higher Cr concentration than the threshold limit value for drinking water of 0.05 mg L^?1. The high Cr concentration in the environment may be responsible for the high concentration of this metal in urine (18.6 ng mL^?1) and hair (4.3 μg g^?1) found in the residents of this polluted area. These results were compared with those of people living in a Cr free zone through statistical analysis (Wilcoxon's signed-ranks test). A significant difference of p<0.01 was found between these two populations. In relation to the average concentrations in hair (1.4 μg g^?1) and urine (2.0 to 6.0 ng mL^?1) considered as normal for a non exposed population in the USA, 70 to 80% of the residents in the Mexican urban-industrial area registered higher values. The high Cr concentration in urine found in workers from the chromite-ore processing plant show the lack of an efficient pollution control system. Therefore the Cr levels found in urine and hair can be used as indicators of environmental exposure.     

Benthic organisms as indicators of water quality in Lake Patzcuaro,Mexico

The water quality was evaluated in Lake Patzcuaro by biological methods using bacteria and macroinvertebrates as indicators, as well as physicochemical parameters. The bacteriological determinations showed critical areas near the two main villages, Patzcuaro and Janitzio. The bacterial ratio FC/FS indicated significant amounts of animal excreta throughout the lake. In areas with less urban influence where there was an abundance of immersed vegetation, the benthic macroinvertebrate community presented high Biotic. Diversity, and Equitability Indices, which were > 2, > 2, and > 0.6, respectively. At the most polluted station (8), Oligochaetes, which are tolerant to organic matter, comprised 94% of the organisms. Physicochemical characteristics are similar in the lake, except at station 8 where the lowest DO levels, highest ammonia and phosphorus concentrations were registered. This area, adjacent to a fish processing plant, is affected by domestic and industrial wastewater discharges. The results show that up to the present the lake has been moderately polluted, but critical zones exist that restrict the use of the lake for water supply and recreational purposes.     

Current Status and Bottle Neck of Octopod Aquaculture: The Case of American Species

The increasing market demand for cephalopods and the experiences obtained with different species has boosted the interest in developing their culture in Latin America. In 2008, an international workshop was held in Puerto Montt, Chile, with 14 experts in experimental cephalopods aquaculture from Brazil, Chile, Spain, and Mexico. Several topics were approached within the holobenthic species Octopus maya and the merobenthic species Enteroctopus megalocyathus, Octopus vulgaris, and Robsonella fontaniana. Part of the conclusions demonstrated that the two greatest difficulties for their production were survival of paralarvae for merobenthic species, and survival of early juveniles for holobenthic species. Besides, there is a need to study the endogenous and exogenous factors affecting health and nutritional status of embryos, paralarvae, and juveniles. These stages, which may limit the culture, should be extensively studied in order to develop the appropriate environmental conditions and culture systems for the physiological and behavioral requirements, from egg incubation up to juveniles to reach a grow‐out phase.     

Root colonization and growth promotion of wheat and maize by Pseudomonas aurantiaca SR1

Wheat (Triticum aestivum L.), rice (Oryza sativa) and maize (Zea mays L.) are the most important cereals worldwide. However, in the last few years, soil has been submitted to both use and handling pressures due to the increase in agricultural practices, which are leading to its degradation. The use of plant growth-promoting rhizobacteria (PGPR) as inoculants constitutes a biological alternative for sustainable production. Pseudomonas aurantiaca SR1 was formulated as an inoculant in order to evaluate its growth promotion effect in the field when applied on maize and wheat seeds at the sowing time. P and N fertilization treatments were also included in the assays. P. aurantiaca SR1 colonized the root system of both crops and it persisted at appropriate population densities. It also showed a significant plant growth-promoting effect that was reflected in the yield. Another relevant finding was that both crops, when inoculated with P. aurantiaca SR1, presented higher yields with fertilization doses lower than those conventionally applied. This indicated its potential use as a reasonable alternative for crop production, with a minimization of the ecological impact.     

Response of alfalfa (Medicago sativa L.) to single and mixed inoculation with phosphate-solubilizing bacteria and Sinorhizobium meliloti

The objectives of this work were to phenotypically and genetically characterize alfalfa rhizosphere bacteria and to evaluate the effect of single or mixed inoculation upon nodulation and biological nitrogen fixation. Thirty-two strains showed tricalcium phosphate solubilization ability, and two of them caused bigger or equal solubilization halos than the control strain P. putida SP22. The comparison of the 16S ribosomal DNA sequences indicated that these strains are phylogenetically related to Bacillus spp. and Pseudomonas spp. A beneficial effect of both isolates on alfalfa growth was observed in coinoculation assays. Pseudomonas sp. FM7d caused a significant increase in root and shoot dry weight, length, and surface area of roots, number, and symbiotic properties of alfalfa plants. The plants coinoculated with Sinorhizobium meliloti B399 and the Bacillus sp. M7c showed significant increases in the measured parameters. Our results indicating that strains Pseudomonas sp. FM7d and Bacillus sp. M7c can be considered for the formulation of new inoculants.     

Serological Survey of Veterinarians to Assess the Zoonotic Potential of Three Emerging Swine Diseases in Mexico

We conducted an immunological assay of blood samples taken from 85 swine‐specialist veterinarians attending the Congress of the Mexican Association of Swine Specialist Veterinarians in Mexico in 2011. Serum samples were assayed for Porcine rubulavirus (PorPV), Encephalomyocarditis virus (EMCV) and Leptospira spp. antibodies. Using a hemagglutination inhibition test, we registered 2.3% and 27% seropositivity for PorPV and EMCV, respectively. Using viral neutralization tests, we registered 5.8% and 47% seropositivity for PorPV and EMCV, respectively. For Leptospira spp., we registered a seropositivity of 38.8%. The variables (sex, age, years of exposure, number of visited farms, biosecurity level and region) showed no significant effect (P > 0.05) on the seropositivity for EMCV, PorPV and Leptospira spp. except for number of visited farms on HI seropositivity for EMCV (P < 0.05; odds ratio: 1.38). The data obtained provide information on the epidemiology of emerging diseases with zoonotic potential in occupational risk groups.     

Effect of different diets on growth and digestive enzyme activity in Litopenaeus vannamei (Boone, 1931) early post-larvae

Growth rate, soluble-protein content and digestive-enzyme activities were studied in Litopenaeus vannamei (Boone, 1931) early post-larvae under six feeding regimens, which included combinations of freshly hatched Artemia nauplii, an artificial diet and algae. Growth (0.11 mg DW day⁻¹) and soluble-protein content (61.8 μg protein larvae⁻¹ at PL₁₀) of post-larvae fed mixed diets were significantly higher (P < 0.05). An artificial diet used alone or co-fed with algae caused the lowest growth (0.03–0.05 mg DW day⁻¹) and soluble-protein content (13.7–15.5 μg protein larvae⁻¹ at PL₁₀). Trypsin-like activity was higher (up to 10 times) in post-larvae fed Artemia nauplii and an artificial diet alone or plus algae. The artificial diet stimulated chymotrypsin activity, apparently in response to squid meal present in this diet. Amylase activity increased when post-larvae were fed the artificial diet. This was apparently related more to the origin of the starch than to the total carbohydrate level of the diet. No obvious relationship was found between enzyme activity and growth in any feed combination. Based on growth and soluble-protein content, we determined that partial substitution (50%) of Artemia nauplii by artificial diet and the use of algae co-fed beyond the first post-larval stage benefits growth and the nutritional state of L. vannamei post-larvae.