L4 Chytridiomycota and Chytridiomycosis Flashcards
What are the defining features of Chytridiomycota?
Chytridiomycota are characterized by the presence of zoospores with a single posterior flagellum, chitin in their cell walls, and the ability to exploit a variety of substrates and hosts.
What types of lifestyles do Chytridiomycota exhibit?
They can be saprophytic, parasitic, or pathogenic, and are primarily found in freshwater and semi-aquatic environments.
Describe the morphological structure of Chytridiomycota.
They form a coenocytic thallus, often including a zoosporangium that produces motile zoospores. They can be epibiotic (on the surface) or endobiotic (inside the substrate).
What are the reproductive strategies of Chytridiomycota?
Most reproduce asexually through zoospores; sexual reproduction is rare but involves fusion of haploid zoospores to form a resting sporangium.
What is Chytridiomycosis, and what causes it?
Chytridiomycosis is a disease in amphibians caused by Batrachochytrium dendrobatidis (Bd), leading to severe declines in amphibian populations worldwide.
What specific tissues does Bd infect in amphibians?
Bd infects keratinized tissues, particularly the mouthparts of tadpoles and the skin of adult amphibians.
What physiological effects does Bd have on amphibians?
The infection thickens the skin (hyperkeratosis), impairs osmoregulation, disrupts respiration, and can lead to electrolyte imbalances and cardiac arrest.
How did Chytridiomycosis first emerge?
It was first observed in Australia and Panama, with the causal agent identified in 1998, leading to declines in approximately 350 amphibian species.
What are the two competing hypotheses for the emergence of Bd?
The Novel Pathogen Hypothesis (Bd is newly introduced) and the Endemic Pathogen Hypothesis (Bd has always been present but became more virulent).
How has Bd spread globally?
Bd is believed to have spread through the global amphibian trade, particularly via infected carriers like Xenopus laevis and Lithobates catesbeiana.
What role do environmental factors play in Bd virulence?
Climate change and habitat alteration may increase amphibian susceptibility to Bd, potentially enhancing its pathogenicity.
What techniques are used to monitor Bd presence in amphibians?
Techniques include quantitative PCR for detecting Bd DNA and swabbing methods to collect samples from amphibians.
What were the findings of the Bd surveillance in British Columbia?
Out of 955 animals swabbed, 150 tested positive for Bd, suggesting widespread distribution and potential transmission methods beyond introduced species.
What genetic findings were associated with Bd?
Whole genome analysis revealed 51,915 SNPs among different Bd isolates, indicating low genetic diversity but multiple introduction events globally.
What are the four major Bd lineages identified worldwide?
The Global Pandemic Lineage (BdGPL), Cape lineage (CAPE), Swiss lineage (CH), and the Asian lineage (BdASIA-1).
How can biosecurity regulations help mitigate the spread of Bd?
Strengthening regulations can limit the movement of infected amphibians, requiring routine screenings in commercial frog farms and trade practices.
What is the impact of Bd on biodiversity?
Bd has caused mass declines and extinctions in amphibian populations, disrupting ecosystems and leading to losses in biodiversity.
Describe the lifecycle of Bd.
The lifecycle includes flagellated zoospores that colonize hosts, develop into thalli, form zoosporangia, and release new zoospores for dispersal.
What is the ecological role of Chytridiomycota?
Chytridiomycota play significant roles as decomposers, parasites, and pathogens, impacting nutrient cycling and host populations in freshwater ecosystems.
What is the significance of the Rhynie Chert in understanding Chytridiomycota?
The Rhynie Chert contains fossils from the Lower Devonian period, showing early parasitic chytrids, which provide insights into the evolution of fungi and their interactions with early land plants.
What are the main modes of zoospore dispersal in Chytridiomycota?
Zoospores disperse primarily through swimming in soil moisture or water, using chemotaxis or possibly phototaxis to locate new substrates.
How does the morphology of Chytridiomycota vary among different taxa?
Morphology can be holocarpic (single zoosporangium) or eucarpic (multiple structures), and can be monocentric (one zoosporangium) or polycentric (multiple zoosporangia).
What are some key challenges in studying Chytridiomycota?
Challenges include their diverse lifestyles, incomplete understanding of their phylogeny, and the difficulties in culturing many species in the laboratory.
Why are amphibians particularly vulnerable to Bd infections?a
amphibians have permeable skin that is crucial for respiration and hydration, making them more susceptible to pathogens that impair these functions.
