Mercury and selenium concentrations in the oysters Saccostrea palmula and Crassostrea corteziensis from four coastal lagoons of NW Mexico: health risk assessment

Mercury (Hg) and selenium (Se) concentrations in the soft tissue of the oysters Saccostrea palmula and Crassostrea corteziensis from four coastal lagoons (Altata, Macapule, Navachiste, El Colorado) of Northwest Mexico were determined. A total of 2520 specimens of S. palmula and 3780 of C. corteziensis (72.15 ± 4.95 and 73.57 ± 5.31 mm, respectively) were sampled seasonally from summer 2019 to spring 2020. The higher Hg concentration (wet weight) for S. palmula (0.13 ± 0.03–0.11 ± 0.02 µg g−1) and C. corteziensis (0.12 ± 0.02–0.11 ± 0.03 µg g−1) were obtained in summer−autumn 2019; Hg level was similar among the coastal lagoons and did not exceed the limit established by Mexican legislation and by the Food and Drug Agency. The higher Se concentration occurred in spring 2020 for both oyster species in El Colorado lagoon (4.55 ± 0.02 and 4.08 ± 0.05 µg g−1, respectively). The Se/Hg molar ratio of S. palmula and C. corteziensis ranged from 48.76–149.59 and 31.72–155.37, respectively; while the Se health benefit value was 19.23–42.28 and 17.82–35.30, respectively. The hazard quotient for Hg -estimated as methylmercury- and Se in both species of oyster was below 1. The high molar ratio obtained (Se/Hg > 1) indicates that the concentration of Se was sufficient to neutralize the possible toxicity of the Hg, therefore, the consumption of S. palmula and C. corteziensis from the four coastal lagoons studied does not represent a risk.

Effect of Flowering Time-Related Genes on Biomass, Harvest Index, and Grain Yield in CIMMYT Elite Spring Bread Wheat

Grain yield (YLD) is a function of the total biomass (BM) and of partitioning the biomass by grains, i.e., the harvest index (HI). The most critical developmental stage for their determination is the flowering time, which mainly depends on the vernalization requirement (Vrn) and photoperiod sensitivity genes (Ppd) loci. Allelic variants at the Vrn, Ppd, and earliness per se (Eps) genes of elite spring wheat genotypes included in High Biomass Association Panel (HiBAP) I and II were used to estimate their effects on the phenological stages BM, HI, and YLD. Each panel was grown for two consecutive years in Northwest Mexico. Spring alleles at Vrn-1 had the largest effect on shortening the time to anthesis, and the Ppd-insensitive allele Ppd-D1a had the most significant positive effect on YLD in both panels. In addition, alleles at TaTOE-B1 and TaFT3-B1 promoted between 3.8% and 7.6% higher YLD and 4.2% and 10.2% higher HI in HiBAP I and II, respectively. When the possible effects of the TaTOE-B1 and TaFT3-B1 alleles on the sink and source traits were explored, the favorable allele at TaTOE-B1 showed positive effects on several sink traits mainly related to grain number. The favorable alleles at TaFT3-B1 followed a different pattern, with positive effects on the traits related to grain weight. The results of this study expanded the wheat breeders’ toolbox in the quest to breed better-adapted and higher-yielding wheat cultivars.

Pachuca Obsidian Blades from the U.S. Southwest: Implications for Mesoamerican Connections and Coronado's Mexican Indian Allies

The connection between people in the prehispanic U.S. Southwest / Northwest Mexico (SW/NW) and Mesoamerica is one of the most debated research topics in American archaeology. SW/NW groups used objects from Mesoamerica, but did they also trade for obsidian? Archaeologists have yet to find Mesoamerican obsidian from confirmed prehispanic SW/NW contexts, but here we discuss four green obsidian prismatic blades from New Mexico and Arizona. Using EDXRF spectrometry, we demonstrate that the blades are from the Pachuca source in Mesoamerica. The blades were found at four sites that the Spanish and their Mexican Indian allies used or potentially visited beginning in AD 1540. Using lithic technological organization and historical narratives, we assess the credibility of the different hypothesized models of prehispanic SW/NW-Mesoamerican interaction and obsidian use by the Mexican Indian allies. We suggest that green Pachuca blades would have been traded into the SW/NW if interaction with Mesoamerica had occurred more frequently. We also offer reasons why archaeologists have found so few Mesoamerican obsidian blades at post-1540 sites. This research is relevant because it expands our knowledge about SW/NW-Mesoamerican connections and the Mexican Indian allies of the Spanish, who are an underrepresented group in the archaeological and historical records.