RESUMO
Nivicolous myxomycetes are a group of amoebozoan protists dependent on long-lasting snow cover worldwide. Recent fine-scale analysis of species diversity from the austral Andes revealed high intraspecific variability of most taxa, suggesting independent evolutionary processes and significant differences in species compositions between the Northern (NH) and Southern (SH) Hemispheres. The present study is the second part of this analysis based on representatives of Trichiales. A total of 173 South American collections were studied based on morphological and molecular data, and 15 taxa have been identified. Two of them, Hemitrichia crassifila and Perichaena patagonica, are proposed as new species confirmed by a phylogeny of Trichiales. However, their affinity to the genera in which they are proposed are not confirmed due to polyphyletic character of all genera of Trichiales. Four species, Dianema subretisporum, Trichia contorta var. karstenii, T. nivicola, and T. sordida, are reported for the first time from the Southern Hemisphere. One species, T. alpina, is new for Argentina. Additionally, we provide the first record of Perichaena megaspora from Chile. Specimen frequency and species diversity of Trichiales found at nivicolous localities in the austral Andes are unexpectedly high, exceeding those of Stemonitidales, the most numerous group in the Northern Hemisphere, where Trichiales play a marginal role. By contrast, Trichiales appear the main component of nivicolous assemblages in the Andes. Results of the present work, together with the earlier analysis of Stemonitidales, indicate that the Andes constitute an exceptionally important evolutionary hot spot for nivicolous myxomycetes characterized by an outstanding species diversity.
Assuntos
Biodiversidade , Mixomicetos/classificação , Argentina , Chile , DNA de Protozoário/genética , Mixomicetos/citologia , Mixomicetos/genética , Mixomicetos/crescimento & desenvolvimento , Fator 1 de Elongação de Peptídeos/genética , Filogenia , RNA Ribossômico 18S/genética , Análise de Sequência de DNA , Neve/parasitologiaRESUMO
We present a novel simulation method to investigate the multicolored effect of the Diachea leucopoda (Physarales order, Myxomycetes class), which is a microorganism that has a characteristic pointillistic iridescent appearance. It was shown that this appearance is of structural origin, and is produced within the peridium -protective layer that encloses the mass of spores-, which is basically a corrugated sheet of a transparent material. The main characteristics of the observed color were explained in terms of interference effects using a simple model of homogeneous planar slab. In this paper we apply a novel simulation method to investigate the electromagnetic response of such structure in more detail, i.e., taking into account the inhomogeneities of the biological material within the peridium and its curvature. We show that both features, which could not be considered within the simplified model, affect the observed color. The proposed method is of great potential for the study of biological structures, which present a high degree of complexity in the geometrical shapes as well as in the materials involved.
Assuntos
Simulação por Computador , Mixomicetos/citologia , Mixomicetos/fisiologia , Óptica e Fotônica/métodos , Fótons , Pigmentação/fisiologia , Mixomicetos/ultraestruturaRESUMO
A new species of Didymium (Myxomycetes), D. operculatum, is described in this paper, and details of its life cycle are provided. The new species was recorded during studies of the Atacama Desert in Chile. It has been collected directly in the field and isolated in moist chamber cultures prepared with material from an endemic cactus. The distinguishing characters of this species are its dehiscence by means of an apical operculum combined with a whitish calcareous stalk and the banded reticulate ornamentation of the spores. The morphology of this new myxomycete was examined with scanning electron microscopy and light microscopy, and micrographs of relevant details are included in this paper. Some comments are made on the patterns of distribution of Didymium species in arid lands and adaptive characters enabling this genus to colonize such extreme environments. It is proposed that a longer cycle and the ability to resort to resistant forms many times during their development reflect the response of these myxomycetes to the largely unfavorable conditions of their environment.