ABSTRACT
Laguna Verde's dome-shaped structures are distinctive formations within the Central Andes, displaying unique geomicrobiological features. This study represents a pioneering investigation into these structures, assessing their formation, associated taxa, and ecological significance. Through a multifaceted approach that includes chemical analysis of the water body, multiscale characterization of the domes, and analysis of the associated microorganisms, we reveal the complex interplay between geology and biology in this extreme environment. The lake's alkaline waters that are rich in dissolved cations and anions such as chloride, sodium sulfate, and potassium, coupled with its location at the margin of the Antofalla salt flat, fed by alluvial fans and hydrothermal input, provide favorable conditions for mineral precipitation and support for the microorganism's activity. Laguna Verde's dome-shaped structures are mainly composed of gypsum and halite, displaying an internal heterogeneous mesostructure consisting of three zones: microcrystalline, organic (orange and green layers), and crystalline. The green layer of the organic zone is predominantly composed of Proteobacteria, Bacteroidetes, and Cyanobacteria, while the orange layer is mostly inhabited by Cyanobacteria. The results of the study suggest that oxygenic photosynthesis performed by Cyanobacteria is the main carbon fixation pathway in the microbial community, supported by carbon isotopic ratios of specific biomarkers. This finding highlights the important role played by Cyanobacteria in this ecosystem.
ABSTRACT
The effect of continuous ivermectin treatment from birth to puberty on growth and reproductive performance was studied in Holstein heifer calves grown on pastures in comparison to naturally nematode-infected, untreated animals. Ivermectin effectively abated the presence of nematode eggs in feces. Eggs per gram (EPG) in parasitized animals increased rapidly from wk 12 to 18 of age and then decreased. Animals treated with ivermectin grew faster than untreated ones, and differences in body weight became significant at 6 wk of life, even before eggs appeared in the feces of either treatment group. Ivermectin-treated heifers reached puberty 3 wk earlier than infected ones as assessed with serum progesterone concentrations (ivermectin, 30.4 +/- .8 vs untreated, 33.7 +/- 1.3 wk of age). This delay was not directly related to body weight. In addition, pelvic area at 39 wk and at 15 mo of age was increased in treated heifers (8 and 11%, respectively) compared with parasitized animals. No differences in the wither heights were observed. We conclude that ivermectin treatment in dairy heifers may increase growth rate during development, advance the onset of ovarian function, and positively affect yearling pelvic area.
