排序方式: 共有64条查询结果,搜索用时 78 毫秒
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Raquel Schier Guerra Mariana Machado Fidelis do Nascimento Stephanie Miesch Mohammad Javad Najafzadeh Raphael Orélis Ribeiro Antonio Ostrensky Gerrit Sybren de Hoog Vania Aparecida Vicente Walter A. Boeger 《Mycopathologia》2013,175(5-6):421-430
Knowledge of natural ecology is essential for a better understanding of pathogenicity and opportunism in black yeast-like fungi. Although etiological agents of diseases caused by these fungi are supposed to originate from the environment, their isolation from nature is difficult. This is probably due to their oligotrophic nature, low competitive ability, and, overall, insufficient data on their natural habitat. We obtained environmental samples from mangrove areas where mortalities by lethargic crab disease (LCD) are reported and areas without disease recorded. Isolation of chaetothyrialean black yeasts and relatives was performed using a highly selective protocol. Species-specific primers were used to determine if these isolates represented Exophiala cancerae or Fonsecaea brasiliensis, two proven agents of LCD, in order to test hypotheses about the origin of the disease. Isolates, identified by morphology as Fonsecaea- or Exophiala-like, were tested specific diagnostic markers for the fungi associated with LCD. Although several black fungi were isolated, the main causative agent of the LCD, E. cancerae, was not found. Molecular markers for F. brasiliensis revealed 10 positive bands for isolates from biofilms on mangrove leaves, branches, and aerial roots, of which four were confirmed by ITS sequencing. The absence of E. cancerae in environmental samples suggests that the species is dependent on the crab, as a genuine pathogen, different from F. brasiliensis, which is probably not dependent on the host species, U. cordatus. However, we did not attempt isolation from the marine water, which may represent the pathway of dispersion of the black yeast species between neighbor mangroves. 相似文献
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Gisela G. Castilho‐Westphal Antonio Ostrensky Marcio R. Pie Walter A. Boeger 《Acta zoologica》2013,94(1):86-93
Ucides cordatus is a species of considerable ecological and socioeconomic importance. The goal of this study is to contribute to the understanding of the reproduction biology of this species by describing the macroscopic anatomy, the histology of the female reproductive system and the reproductive cycle of U. cordatus. A total of 367 females were obtained from October of 2002 to March of 2005 during monthly collections in the Baía de Antonina, Paraná, Brazil. Specimens were submitted to necropsy and their reproductive systems (ovary and spermathecae) were analysed histologically. Permanent slides were stained with Harris' hematoxylin and eosin, Mallory's trichromic and the periodic acid‐Schiff reaction. Ovarian analysis allowed for the determination of five developmental stages based on the prevalence of oocytes in different phases of vitellogenesis. During stage V, when ovaries recover from spawning, the presence of oocytes in advanced stages of vitellogenesis was detected, suggesting that there could be more than one spawning in a single reproductive period. Females in stage IV were most common in the spring (November through February), whereas females with their egg mass exposed were most frequent from November through March. The reproductive period of U. cordatus in mangroves of the study region occurred from October to March. The reproductive events observed in the present study suggest that spermatophores acquired during copulation, which takes place during the ‘andada’, are only used in the reproductive period of the following year. 相似文献
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Euryhaliotrema dontykoleos n. sp. (Monogenoidea, Polyonchoinea, Dactylogyridae) is described based on specimens collected from the gills of Pachyurus junki (Teleostei, Sciaenidae, Pachyurinae) in the Rio Tocantins and its tributaries, State of Tocantins, Brazil. The new species, the first species of Monogenoidea reported from a pachyurine, is easily differentiated from its congener by the presence of toothlike projections in the border of the vaginal opening and by having a trapezoidal anteromedial projection on the ventral bar. Phylogenetic analysis indicates that the new species is not a member of the clade that includes the Euryhaliotrema spp. from Plagioscion spp., a second lineage of freshwater sciaenids in South America. Euryhaliotrema dontykoleos shares an immediate ancestor with the clade formed by parasites infecting marine Paralonchurus spp., (Sciaenidae), and those of Plagioscion spp. 相似文献
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Although lethargic crab disease (LCD) is causing massive mortalities in populations of the mangrove crab Ucides cordatus of Northeastern Brazil, the identity of its etiological agent was hitherto unknown. In this study we provide robust evidence suggesting that LCD is caused by an anamorph Ascomycota (Fungi). We examined specimens of U. cordatus collected from stocks affected by LCD. Histological and TEM methods detected the presence of hyphae, conidia, and condiophores in several host tissues. Moreover, the abundance of fungal stages is negatively associated with crab health. Finally, DNA was isolated from the fungus and a region of its 18S ribosomal gene was sequenced Phylogenetic analyses not only confirm the diagnosis of the LCD fungus in crab tissues as an ascomycete, but also suggest a close relationship with members of the subphylum Pezizomycotina. 相似文献
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Response of photosynthesis to high light and drought for Arabidopsis thaliana grown under a UV-B enhanced light regime 总被引:1,自引:0,他引:1
Arabidopsis thaliana grown in a light regime that included ultraviolet-B (UV-B) radiation (6 kJ m−2 d−1) had similar light-saturated photosynthetic rates but up to 50% lower stomatal conductance rates, as compared to plants grown
without UV-B radiation. Growth responses of Arabidopsis to UV-B radiation included lower leaf area (25%) and biomass (10%)
and higher UV-B absorbing compounds (30%) and chlorophyll content (52%). Lower stomatal conductance rates for plants grown
with UV-B radiation were, in part, due to lower stomatal density on the adaxial surface. Plants grown with UV-B radiation
had more capacity to down regulate photochemical efficiency of photosystem II (PSII) as shown by up to 25% lower φPSII and 30% higher non-photochemical quenching of chlorophyll fluorescence under saturating light. These contributed to a smaller
reduction in the maximum photochemical efficiency of PSII (F
v/F
m), greater dark-recovery of F
v/F
m, and higher light-saturated carbon assimilation and stomatal conductance and transpiration rates after a four-hour high light
treatment for plants grown with UV-B radiation. Plants grown with UV-B were more tolerant to a 12 day drought treatment than
plants grown without UV-B as indicated by two times higher photosynthetic rates and 12% higher relative water content. UV-B-grown
plants also had three times higher proline content. Higher tolerance to drought stress for Arabidopsis plants grown under
UV-B radiation may be attributed to both increased proline content and decreased stomatal conductance. Growth of Arabidopsis
in a UV-B-enhanced light regime increased tolerance to high light exposure and drought stress. 相似文献
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Host use dynamics in a heterogeneous fitness landscape generates oscillations in host range and diversification 下载免费PDF全文
Mariana P. Braga Sabrina B. L. Araujo Salvatore Agosta Daniel Brooks Eric Hoberg Sören Nylin Niklas Janz Walter A. Boeger 《Evolution; international journal of organic evolution》2018,72(9):1773-1783
Colonization of novel hosts is thought to play an important role in parasite diversification, yet little consensus has been achieved about the macroevolutionary consequences of changes in host use. Here, we offer a mechanistic basis for the origins of parasite diversity by simulating lineages evolved in silico. We describe an individual‐based model in which (i) parasites undergo sexual reproduction limited by genetic proximity, (ii) hosts are uniformly distributed along a one‐dimensional resource gradient, and (iii) host use is determined by the interaction between the phenotype of the parasite and a heterogeneous fitness landscape. We found two main effects of host use on the evolution of a parasite lineage. First, the colonization of a novel host allowed parasites to explore new areas of the resource space, increasing phenotypic and genotypic variation. Second, hosts produced heterogeneity in the parasite fitness landscape, which led to reproductive isolation and therefore, speciation. As a validation of the model, we analyzed empirical data from Nymphalidae butterflies and their host plants. We then assessed the number of hosts used by parasite lineages and the diversity of resources they encompass. In both simulated and empirical systems, host diversity emerged as the main predictor of parasite species richness. 相似文献
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