Oligotrophy: the forgotten end of an ecological spectrum

Most studies that consider the relationship of diatoms and water quality have focused their attention on the questions and practicalities of water pollution or perturbations in some form or another. Many models and studies have demonstrated the environmental tolerances or changes in structure of diatom communities related to environmental challenges. This focus on the impacted end of the water quality spectrum has led, of necessity, to issues ultimately related to habitat restoration. We contend that a concentrated effort to develop more fully the theory and there is a need for practice related to oligotrophy, the other, ignored end of the water quality spectrum. We explore the historical usages of the term oligotrophy, as well as the challenges and promise of autecological and community approaches to understanding oligotrophy, and the possibility of focusing more on conservation rather than restoration in water quality issues

Epilithic diatoms (Bacillariophyta) from cloud forest and alpine streams in Bolivia, South America II: A preliminary report on the diatoms from Sorata, Department of La Paz

Un total de siete muestras de epiHton fueron colectadas en rios dentro de ungradiente altitudinal en el bosque nublado de Bokvia, cerca de la capital La Paz. Laflora diatomologica es diversa v no se encontraron patrones altitudinales claros. Talflora esta compuesta por especies cosmopolitas y taxa restringidos a los Andes con losgeneros Gompbonema, Nit^schia, Engonopsis v Engonema agrupando al mayor numero deespecies e individuos con mayores frecuencias. La flora esta tambien representada porvarios taxa alcalifilos y alcaKbiontes, reflejando los altos valores de pH de los rios. Las caracteristicas de los sitios muestreados, asi como una lista de taxa y figurasrepresentativas se presentan en este trabajo

Search for new synthetic immunosuppressants II. Tetrazole analogues of hymenistatin I

Linear and cyclic hymenistatin I (HS I) analogues with dipeptide segments Ile2-Pro3, Pro3-Pro4 and Val6-Pro7 replaced by their tetrazole analogues Ile-Ψ[CN4]-Ala3, Pro3-Ψ[CN4]-Ala4 and Val6-Ψ[CN4]-Alawere synthesized by the solid phase peptide synthesis method and cyclized with the TBTU and/or HATU reagent. The peptides were examined for their immunosuppressive activity in the lymphocyte proliferation test (LPT)

A new, large species of Gomphonema Ehrenberg from ancient Lake Matano, Indonesia

© 2018, © 2018 The International Society for Diatom Research. A large species of the diatom genus Gomphonema Ehrenberg, G. matanensis sp. nov., is described as new to science from ancient Lake Matano, Indonesia. Light and scanning electron microscopic observations of the valve morphology of this species are presented. The morphology of this species is similar to other large species that have ovoid areolar openings without external flaps or occlusions, such as G. gomphopleuroides Amossé ex Kociolek, Glushchenko & Kulikovskiy and members of the G. kaznakowi species complex, both known from Southeast Asia. This species has the special features of bi- and triradiate siliceous growths at the valve mantle junction, continuing onto the mantle. Though an analysis of the phylogenetic relationships of the diatom genus Gomphonema is currently wanting, it would appear that gigantism occurred several times within the genus

Historical and Current Perspectives on the Systematics of the ‘Enigmatic’ Diatom Genus Rhoicosphenia (Bacillariophyta), with Single and Multi-Molecular Marker and Morphological Analyses and Discussion on the Monophyly of ‘Monoraphid’ Diatoms

This study seeks to determine the phylogenetic position of the diatom genus Rhoicosphenia. Currently, four hypotheses based on the morphology of the siliceous valve and its various ultrastructural components, sexual reproduction, and chloroplasts have been proposed. Two previous morphological studies have tentatively placed Rhoicosphenia near members of the Achnanthidiaceae and Gomphonemataceae, and no molecular studies have been completed. The position of Rhoicosphenia as sister to &lsquo;monoraphid&rsquo; diatoms is problematic due to the apparent non-monophyly of that group, so hypotheses of &lsquo;monoraphid&rsquo; monophyly are also tested. Using an analysis of morphological and cytological features, as well as sequences from three genes, SSU, LSU, and rbcL, recovered from several freshwater Rhoicosphenia populations that have similar morphology to Rhoicosphenia abbreviata (Agardh) Lange-Bertalot, we have analyzed the phylogenetic position of Rhoicosphenia in the context of raphid diatoms. Further, we have used topology testing to determine the statistical likelihoods of these relationships. The hypothesis that Rhoicosphenia is a member of the Achnanthidiaceae cannot be rejected, while the hypothesis that it is a member of the Gomphonemataceae can be rejected. In our analyses, members of the Achnanthidiaceae are basal to Rhoicosphenia, and Rhoicosphenia is basal to the Cymbellales, or a basal member of the Cymbellales, which includes the Gomphonemataceae. Hypothesis testing rejects the monophyly of &lsquo;monoraphid&rsquo; diatoms.</p

Epilithic diatoms (Bacillariophyta) from cloud forest and alpine streams in Bolivia, South America 3: diatoms from Sehuencas, Carrasco National Park, Department of Cochabamba

Studies on Bolivian diatoms are scarce and they do not represent the great geographic variability of the country. One of the regions with the highest biological diversity in Bolivia is the Yungas (cloud forest), a 90.500 km2 strip located between the Andean Puna and the Amazonian lowlands. The Carrasco National Park is the park with the largest extension of Yungas within its boundaries. This park is located east from Cochabamba, the third largest city in Bolivia, and has an area of ca 6.226 km2, serving as a refuge to 5.000 recorded species of plants and more than 300 species of vertebrates. Very little is known about the aquatic biota in the zone and there are no studies on diatoms. One of the preferred tourist spots within the park is Sehuencas, located 17°31\u2742" S and 65°16\u2717" W and characterized by numerous lotic waterbodies. The present work was carried on 5 epilithic samples from which 118 species, varieties and forms were identified using light (LM) and scanning electron microscopy (SEM). Forty-two (36%) of these taxa were not found in the literature for South America or other regions of the world. This high percentage of unknown taxa suggests a high potential for the contribution of new organisms to science, many of which are possibly endemic to the region, thus justifying an additional effort to preserve the aquatic habitats in the park. Two new species are described herein (Fragilaria cochabambina Morales sp. nov. and Achnanthidium sehuencoensis Morales.sp. nov.) and comparisons with published morphologically similar taxa are presented. Unknowns remain undescribed until larger populations that allow detailed LM and SEM studies are found

Longitudinal decline in semantic versus letter fluency, but not their ratio, marks incident Alzheimer’s disease in Latinx Spanish-speaking older individuals

Objective: To compare longitudinal verbal fluency performance among Latinx Spanish speakers who develop Alzheimer’s disease to those who do not develop dementia in absolute number of words produced on each task and their ratio to combine both scores. Method: Participants included 833 Latinx Spanish-speaking older adults from a community-based prospective cohort in Manhattan. We performed growth curve modeling to investigate the trajectories of letter and semantic fluency, and their ratio (i.e., ‘semantic index’), between individuals who developed Alzheimer’s disease and those who did not (i.e., controls). The semantic index quantifies the proportion of words generated for semantic fluency in relation to the total verbal fluency performance. Results: Letter fluency performance did not decline in controls; we observed a linear decline in those who developed Alzheimer’s disease. Semantic fluency declined in both groups and showed an increased rate of change over time in the incident Alzheimer’s disease group; in comparison, the control group had a linear and slower decline. There were no group differences in the longitudinal trajectory (intercept and slope) of the semantic index. Conclusion: A decline in letter fluency and a more rapid and accelerating decline over time in semantic fluency distinguished people who developed Alzheimer’s disease from controls. Using the semantic index was not a superior marker of incident Alzheimer’s disease compared to examining the two fluency scores individually. Results suggest the differential decline in verbal fluency tasks, when evaluated appropriately, may be useful for early identification of Alzheimer’s disease in Latinx Spanish speakers, a historically understudied population. Keywords: category fluency, phonemic fluency, language, dementia, Hispani

New species, new taxon report and biogeography of the diatom genus <i>Gomphoneis</i> Cleve (Bacillariophyceae) in Patagonia, Chubut Province, Argentina

The presence of three Gomphoneis species from Chubut Province in Argentina is documented with light and scanning electron microscopy. Two of the taxa, G. patagoniana and G. eriense var. variabilis, are part of the Herculeana subgroup of Gomphoneis. Gomphoneis patagoniana is a newly discovered species and G. eriense var. variabilis is reported from Argentina for the first time. These two species have evident axial plates, differentiated apical pore fields (APFs), a stigmal opening that is round externally and slit-like internally, and areolae that are mostly triradiate in shape. The third species, G. frenguellii, is also newly discovered and described. Presence of four isolated stigmoids, undifferentiated APFs and lack of an axial plate indicates G. frenguellii is a member of the Elegans subgroup of the genus. Presence of these newly described species, and the previously unreported taxon, may also be associated with the invasive species Didymosphenia geminata. Given there is no long history of reports of Gomphoneis in the country and, in the case of G. eriense var. variabilis, its previously known distribution, it is possible that the origin of this Gomphoneis taxon is from western North America.Facultad de Ciencias Naturales y Muse