Spore ultrastructure in Sporothrix schenckii

Pathogenic strains of Sporothrix schenkii may show triangular spores, whose angular shape is maintained by a tiebeam effect in the inner cell wall structure. This difference in wall structure lies adjacent to a folded and possibly more active part of the spore cytoplasm. The supposed generation of asci in old cultures was simulated by the death of hyphae which are reinvaded by intrahyphal growth with intrahyphal spore production, while true asci were not seen.     

Ants impact the composition of the aquatic macroinvertebrate communities of a myrmecophytic tank bromeliad

In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks.     

The book reopened on infectious diseases

Emerging infectious diseases represent a major challenge to human health worldwide. The risk of evolving new infectious pathogens has been intensifying due to urbanization, demographic changes, air travel, inappropriate use of antibiotics, and climate change. These pathogens can affect humans from urban centers to the remotest corners of the globe. Far from being a scourge of the past, infectious diseases are relevant for the world today.     

Changes in diatom-dominated biofilms during simulated improvements in water quality: implications for diatom-based monitoring in rivers

Although benthic diatoms are used to assess river water quality, there are few data on the rate at which diatom assemblages react to changes in water quality. The aim of this study was to assess the reaction time of diatoms and to discuss the changes occurring during water quality improvement on the basis of their autecological characteristics. In order to simulate this improvement, diatom-dominated biofilms grown on artificial sandstone substrata were transferred from several polluted rivers to an unpolluted river. They were sampled three times: before transfer and 1 and 2 months after transfer. The ecology and growth-forms of the taxa explained most of the changes in species composition observed during the experiment. Adnate diatoms gradually replaced motile and stalked taxa. Gomphonema parvulum, a stalked diatom positioned vertically in the biofilm, is adapted for light and space competition in high-density algal biofilms. When transferred to an unpolluted site, this growth-form is less competitive and does not tolerate the high grazing pressure. Fistulifera saprophila is a single celled motile diatom, living in organic matrices. When the artificial substrata were transferred to the unpolluted site, this particular ecological niche disappeared quickly. On the other hand, Achnanthidium minutissimum, which is considered to be cosmopolitan and an early colonizer, increased during the first month of transfer and then decreased. It was gradually replaced by A. biasolettianum, which was the taxon best suited to this pristine stream. The changes observed differed between treatments depending on the species composition and architecture of the biofilms. In particular, biofilms dominated by stalked and motile diatoms were more quickly modified than those dominated by small motile diatoms. The diatom index reflects these changes, and its values showed that about 60 days following a water quality improvement were necessary for transferred diatom assemblages to reach diatom index values similar as those at the unpolluted river.     

Re-infestation of houses by Triatoma dimidiata after intra-domicile insecticide application in the Yucatán peninsula, Mexico

In most countries, Chagas disease transmission control remains based on domestic insecticide application. We thus evaluated the efficacy of intra-domicile cyfluthrin spraying for the control of Triatoma dimidiata, the only Chagas disease vector in the Yucatán peninsula, Mexico, and monitored potential re-infestation every 15 days for up to 9 months. We found that there was a re-infestation of houses by adult bugs starting 4 months after insecticide application, possibly from sylvatic/peridomicile areas. This points out the need to take into account the potential dispersal of sylvatic/peridomestic adult bugs into the domiciles as well as continuity action for an effective vector control.