Arachnitis Research Articles

Ancient climate changes and Andes uplift, rather than Last Glacial Maximum, affected distribution and genetic diversity patterns of the southernmost mycoheterotrophic plant Arachnitis uniflora Phil. (Corsiaceae)

Arachnitis uniflora (Corsiaceae) is a mycoheterotrophic plant native to South America that grows in tropical semi-humid forests of Peru and Bolivia, in the temperate Andean-Patagonian forests of Argentina and Chile, and in the moorlands of Malvinas/Falkland Islands. This widely distributed and disjunct species offers the opportunity to explore the dynamics of evolutionary processes using phylogeographic approaches, spatio-temporal and paleodistribution reconstructions; these tools allow us to test how ancient geological events and climate changes occurred in the Miocene-Pliocene and how the more recent Pleistocene events affected diversification, demography, and genetic diversity patterns over space and time. We sampled 28 sites, covering the whole geographic range of Arachnitis uniflora . We amplified and sequenced the internal transcribed spacer (ITS), 18S rRNA, and 26S rRNA nuclear regions in 141 individuals, and the plastid 16S rRNA gene in a subset of 90 individuals. In order to reconstruct the evolutionary history of the species, we performed phylogeographic, dating analyses, spatio-temporal diffusion models, and species paleo-distribution projections. Arachnitis uniflora has an ancient origin and diversified during the Late Miocene, splitting into two genetic groups named the Northern and Patagonian groups. Haplotype diversification of both groups dated about late Miocene and early Pliocene. We detected demographic expansion at the early Pleistocene, and most diversifications and colonizations occurred before the LGM. Paleo-distribution modelling predicted few changes of the species distribution from 800 Mya to the present, showing only a range expansion at the east during the LGM. Four areas of high genetic diversity were identified suggesting refugial areas where the species persisted. Orogeny and climate changes promoted by the Andes uplift during the Late Miocene produced the main ancient genetic divergence due to the formation of the Arid Diagonal. Most diversification, colonizations, and demographic processes occurred from early Pliocene to the beginning of the Pleistocene before the Great Patagonian Glaciation, revealing a low influence of the LGM glaciations on the species evolutionary history. • First study on the evolutionary history of a mycoheterotrophic plant species • Genetic divergence in correlation with the formation of the Arid Diagonal • Andes uplift rather than Pleistocene glaciations were responsible for main diversifications. • Hotspots areas are coincident with those recovered for its fungal symbiont.

Root-Associated Fungal Communities in Two Populations of the Fully Mycoheterotrophic Plant Arachnitis uniflora Phil. (Corsiaceae) in Southern Chile.

The microbiological interactions of the roots of non-photosynthetic plants in South America have been scarcely explored. This study analyzes culturable fungal diversity associated with the mycoheterotrophic plant Arachnitis uniflora Phil. (Corsiaceae) in southern Chile, growing in two different understoreys of native (Nothofagus-dominated) and mixed forest (native, Cupressus sempervirens, and Pinus radiata). Rhizospheric and endophytic fungi were isolated, cultured, and purified to identify microorganisms associated with A. uniflora roots. We showed the different fungi associated with the plant, and that these distributions are influenced by the sampling site. We isolated 410 fungal strains (144 endophytic and 266 from the rhizosphere). We identified 13 operative taxonomical units from plants sampled in the mixed forest, while 15 were from the native forest. Rhizospheric microorganisms were mainly related to Penicillium spp., whereas some pathogenic and saprophytic strains were more frequent inside the roots. Our results have also shown that the fungal strains are weak for phosphate solubilization, but other pathways such as organic acid exudation and indole acetic acid production can be considered as major mechanisms to stimulate plant growth. Our results point to new fungal associates of A. uniflora plants reported in Andean ecosystems, identifying new beneficial endophytic fungi associated with roots of this fully mycoheterotrophic plant.

Genetic diversity patterns of arbuscular mycorrhizal fungi associated with the mycoheterotroph Arachnitis uniflora Phil. (Corsiaceae).

Arachnitis uniflora is a mycoheterotrophic plant that exploits arbuscular mycorrhizal fungi of neighbouring plants. We tested A. uniflora 's specificity towards fungi across its large latitudinal range, as well as the role of historical events and current environmental, geographical and altitudinal variables on fungal genetic diversity. Arachnitis uniflora mycorrhizas were sampled at 25 sites. Fungal phylogenetic relationships were reconstructed, genetic diversity was calculated and the main divergent lineages were dated. Phylogeographical analysis was performed with the main fungal clade. Fungal diversity correlations with environmental factors were investigated. Glomeraceae fungi dominated, with a main clade that likely originated in the Upper Cretaceous and diversified in the Miocene. Two other arbuscular mycorrhizal fungal families not previously known to be targeted by A. uniflora were detected rarely and appear to be facultative associations. High genetic diversity, found in Bolivia and both northern and southern Patagonia, was correlated with temperature, rainfall and soil features. Fungal genetic diversity and its distribution can be explained by the ancient evolutionary history of the target fungi and by micro-scale environmental conditions with a geographical mosaic pattern.

The mycoheterotroph Arachnitis uniflora has a unique association with arbuscular mycorrhizal fungi

Achlorophyllous plants that are dependent on an association with fungi linked to photosynthetic plants for their carbon source are known as mycoheterotrophs. Arachnitis uniflora Phil., a monotypic member of the monocotyledonous family Corsiaceae, fits this category, as it relies on a glomalean fungus belonging to Glomus Group A for carbon acquisition. Although basic structural features of root colonization have been reported for A. uniflora, the nutrient exchange interface has not been studied. This is the first study to use confocal microscopy, transmission electron microscopy, and cytochemical procedures to study the interface between a glomalean fungus and the roots of a mycoheterotrophic species. Results showed that arbuscules are never formed, and that the “vesicles in bundles” reported earlier are unlike typical glomalean vesicles, in that they form in clusters by the enlargement of hyphal branches and have a complex multilayered wall. The thick inner wall layer consists primarily of β-1,3-glucans (callose) and is surrounded by a thin outer layer of chitin. Each structure is surrounded by host cell wall material and a perifungal membrane, suggesting an involvement in nutrient exchange. The cytoplasm contains a complex of small β-1,3-glucan-containing vacuoles, lipid bodies, endobacteria, and many nuclei. These structures enlarge to occupy most of the cortical cell volume and then degrade, releasing lipids and other materials into the host cell. We suggest that these structures should not be equated with typical glomalean vesicles but are unique structures that may be involved, along with the hyphal coils, in nutrient acquisition by the host.

‘Prepackaged symbioses’: propagules on roots of the myco‐heterotrophic plant Arachnitis uniflora

Arachnitis uniflora, a myco-heterotrophic plant species, has fleshy tuberous roots colonized by the arbuscular mycorrhizal fungal genus Glomus (Phylum Glomeromycota). These roots produce apical and lateral propagules, both reported here for the first time. The objective of the study was to characterize the ontogeny and structure of the propagules, and to determine their function. Scanning electron microscopy, laser scanning confocal microscopy and light microscopy were used to study the ontogeny and structure of the propagules. Propagules developed either from cortical parenchyma cells or from cells immediately beneath the root cap; they developed a shoot meristem and cells in the basal region which were colonized by various fungal structures including hyphae and vesicles. These propagules may detach from the roots, establishing new plants.

The southernmost myco-heterotrophic plant, Arachnitis uniflora: root morphology and anatomy

Root morphology and anatomy of the myco-heterotrophic Arachnitis uniflora (Corsiaceae) were studied in relation to their association with a Glomus species (Glomeromycota). The mycorrhizal features were studied in three distinctive stages of development: (i) shoot and flower restricted to a small, underground bud; (ii) shoot and flower bud up to 1.5 cm; and (iii) shoot and flower already withered. The hyphae penetrate through and between the epidermal and exodermal cells; the exodermis and outer cortical cells become colonized in an inter- and intracellular manner, with some coils being formed in these layers. The fungi colonize the middle cortex, where intracellular vesicles in bundles are abundant. Arbuscules are formed profusely at very early stages of development, while in older stages they almost disappear and abundant vesicles are formed. Except for some details, the pattern of root colonization corresponds to a Paris-type. Presence of storage substances (starch and oil) also was recorded. Starch is produced and stored within root cells, mainly in the outer and inner root cortex. In senescent stages, plant and fungal tissues collapse.

Epiparasitic plants specialized on arbuscular mycorrhizal fungi.

Over 400 non-photosynthetic species from 10 families of vascular plants obtain their carbon from fungi and are thus defined as myco-heterotrophs. Many of these plants are epiparasitic on green plants from which they obtain carbon by 'cheating' shared mycorrhizal fungi. Epiparasitic plants examined to date depend on ectomycorrhizal fungi for carbon transfer and exhibit exceptional specificity for these fungi, but for most myco-heterotrophs neither the identity of the fungi nor the sources of their carbon are known. Because many myco-heterotrophs grow in forests dominated by plants associated with arbuscular mycorrhizal fungi (AMF; phylum Glomeromycota), we proposed that epiparasitism would occur also between plants linked by AMF. On a global scale AMF form the most widespread mycorrhizae, thus the ability of plants to cheat this symbiosis would be highly significant. We analysed mycorrhizae from three populations of Arachnitis uniflora (Corsiaceae, Monocotyledonae), five Voyria species and one Voyriella species (Gentianaceae, Dicotyledonae), and neighbouring green plants. Here we show that non-photosynthetic plants associate with AMF and can display the characteristic specificity of epiparasites. This suggests that AMF mediate significant inter-plant carbon transfer in nature.

New Records of Pteridophytes from Bolivia

New Records of Pteridophytes from Bolivia

Statistical Survey of Unilateral Sensori-Neural Deafness

The clinical histories, results of auditory and vestibular examinations of 75 cases, mostly adults, with unilateral sensori-neural deafness of obscure etiology were discussed, and their clinical pictures were presented.Fourty-six cases (61.3%) indicated sensory hearing loss and had many past histories as intrinsic or extrinsic factors such as hypertension, head injury, gastric ulcer, allergy, gynecological surgery, Streptomycin injection, and diabetes mellitus.Five cases (6.7%) indicated sensory and retrocochlear hearing loss simultaneously, 11 cases (14.7%) indicated retrocochlear hearing loss, and 13 cases (17.3%) were unclassified.Some cases with retrocochlear hearing loss of obscure etiology showed probabilities of cerebellopontine angle arachnitis and 46.7% of the patients complained of vertiginous symptoms, and 46.6% showed canal parasis in bithermal caloric examination.Further investigations will be necessary about anatomical and morphological differences in the cases of obscure etiology.

Pilzmückenblumen als Pilzmimeten

Observations covering a period of several years have shown that Asarum caudatum is regularly pollinated by fungus gnats. Thereby attention was directed to certain appendages resembling mushrooms or parts thereof, occurring on perianths, axes, or bracts of ecologically related flowers. A hypothesis is being put forward that these appendages are dummies for deceptive attraction of fungivorous Diptera such as Mycetophilids, Sciarids, etc., to ensure cross pollination by these insects. In Asarum spp. as well as in the Aroids Arisarum proboscideum and Arisaema utile, this function has been substantiated by direct proof. By analogy, or from observations of related, non-mimetic species, the visit of fungus gnats is equally predicted for Aristolochia arborea, species of the Orchid genera Masdevallia (sect. Chimaeroideae), Cypripedium and Corybas, the section Trisecta of Arisaema, and Arachnitis uniflora, member of Corsiaceae, all of them mimicking fungus parts, too. The fungus mimetes - as fungus gnat flowers, in general, a hitherto undescribed subclass of the myiophilous style - are dwellers of the dark forest floor, with blossoms close to the bottom (geophily), of dark purple brown hues as a rule and white or translucent patterns, of seeming scentlessness or mushroom-like and musky odors, and intensive local transpiration of the fungus-like parts. They are urn-shaped or kettle-traps of a simple type. The fungus gnats whose relation to mushrooms is discussed regarding its parasitic ultilization by the deception flowers, approach the latter on account of their breeding instincts. Misled by their releasing system involving olfactory, light, tactile and humidity perception, the midges lay their eggs (or try to do so) into the lamella or pore imitations and thus they pollinate the flower. Eggs and larvae, incapable of eating the flower tissue, die before anthesis is finished. Mating males of the gnats also contribute to pollination. Counts of the eggs and larvae in Asarum caudatum flowers resulted in visit rates up to 76 % of the flowers in cultivation and up to 35 % in natural surroundings. Infected flowers contained 4 eggs on the average. Mostly not more than one egg is laid per oviposition. Fungus gnat visits in Asarum caudatum continue during the first five days, fade then, and finish completely, after anthesis - of 9—12 days total duration — has come to an end. Allogamy by the help of fungus gnats is presumed to be a general feature of Asarum (incl. Heterotropa), a genus in which fungus-like structures occur in 8 of its sections

Mielocintilografia com RIHSA no diagnóstico de processos patológicos intra-raqueanos

O estudo de 214 mielocintilografias feitas em 200 pacientes permitiu aos autores chegar às seguintes conclusões: 1) a mielocintilografia com RIHSA - 131I oferece novas possibilidades no campo do diagnóstico neurológico, principalmente no que tange aos processos expansivos, inflamatorios e malformações, sendo limitadas suas possibilidades no diagnóstico de hérnias dos núcleos pulposos; 2) a mielocintilografia não substitui métodos mielográficos convencionais, os dois métodos devendo ser usados de maneira a se completarem; 3) há casos em que a mielocintilografia com RIHSA apresenta vantagem sobre a mielografia com os meios de contraste positivos, principalmente no diagnóstico de aracnoidites, avulsões de raízes e malformações do canal vertebral; 4) a mielocintilografia com RIHSA tornou-se um método de uso corrente no diagnóstico neurológico, devido à facilidade de execução do exame, à boa tolerância desta substância pelo organismo, à sua rápida absorção e completa eliminação.

DDT aids protective strategy

Observations covering a period of several years have shown that Asarum caudatum is regularly pollinated by fungus gnats. Thereby attention was directed to certain appendages resembling mushrooms or parts thereof, occurring on perianths, axes, or bracts of ecologically related flowers.A hypothesis is being put forward that these appendages are dummies for deceptive attraction of fungivorous Diptera such as Mycetophilids, Sciarids, etc., to ensure cross pollination by these insects.In Asarum spp. as well as in the Aroids Arisarum proboscideum and Arisaema utile, this function has been substantiated by direct proof. By analogy, or from observations of related, non-mimetic species, the visit of fungus gnats is equally predicted for Aristolochia arborea, species of the Orchid genera Masdevallia (sect. Chimaeroideae), Cypripedium and Corybas, the section Trisecta of Arisaema, and Arachnitis uniflora, member of Corsiaceae, all of them mimicking fungus parts, too.The fungus mimetes - as fungus gnat flowers, in general, a hitherto undescribed subclass of the myiophilous style - are dwellers of the dark forest floor, with blossoms close to the bottom (geophily), of dark purple brown hues as a rule and white or translucent patterns, of seeming scentlessness or mushroom-like and musky odors, and intensive local transpiration of the fungus-like parts. They are urn-shaped or kettle-traps of a simple type.The fungus gnats whose relation to mushrooms is discussed regarding its parasitic ultilization by the deception flowers, approach the latter on account of their breeding instincts. Misled by their releasing system involving olfactory, light, tactile and humidity perception, the midges lay their eggs (or try to do so) into the lamella or pore imitations and thus they pollinate the flower. Eggs and larvae, incapable of eating the flower tissue, die before anthesis is finished. Mating males of the gnats also contribute to pollination.Counts of the eggs and larvae in Asarum caudatum flowers resulted in visit rates up to 76 % of the flowers in cultivation and up to 35 % in natural surroundings. Infected flowers contained 4 eggs on the average. Mostly not more than one egg is laid per oviposition. Fungus gnat visits in Asarum caudatum continue during the first five days, fade then, and finish completely, after anthesis - of 9—12 days total duration — has come to an end. Allogamy by the help of fungus gnats is presumed to be a general feature of Asarum (incl. Heterotropa), a genus in which fungus-like structures occur in 8 of its sections