L4 Chytridiomycota and Chytridiomycosis

Question 1

What are the defining features of Chytridiomycota?

Answer 1

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.

Question 2

What types of lifestyles do Chytridiomycota exhibit?

Answer 2

They can be saprophytic, parasitic, or pathogenic, and are primarily found in freshwater and semi-aquatic environments.

Question 3

Describe the morphological structure of Chytridiomycota.

Answer 3

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).

Question 4

What are the reproductive strategies of Chytridiomycota?

Answer 4

Most reproduce asexually through zoospores; sexual reproduction is rare but involves fusion of haploid zoospores to form a resting sporangium.

Question 5

What is Chytridiomycosis, and what causes it?

Answer 5

Chytridiomycosis is a disease in amphibians caused by Batrachochytrium dendrobatidis (Bd), leading to severe declines in amphibian populations worldwide.

Question 6

What specific tissues does Bd infect in amphibians?

Answer 6

Bd infects keratinized tissues, particularly the mouthparts of tadpoles and the skin of adult amphibians.

Question 7

What physiological effects does Bd have on amphibians?

Answer 7

The infection thickens the skin (hyperkeratosis), impairs osmoregulation, disrupts respiration, and can lead to electrolyte imbalances and cardiac arrest.

Question 8

How did Chytridiomycosis first emerge?

Answer 8

It was first observed in Australia and Panama, with the causal agent identified in 1998, leading to declines in approximately 350 amphibian species.

Question 9

What are the two competing hypotheses for the emergence of Bd?

Answer 9

The Novel Pathogen Hypothesis (Bd is newly introduced) and the Endemic Pathogen Hypothesis (Bd has always been present but became more virulent).

Question 10

How has Bd spread globally?

Answer 10

Bd is believed to have spread through the global amphibian trade, particularly via infected carriers like Xenopus laevis and Lithobates catesbeiana.

Question 11

What role do environmental factors play in Bd virulence?

Answer 11

Climate change and habitat alteration may increase amphibian susceptibility to Bd, potentially enhancing its pathogenicity.

Question 12

What techniques are used to monitor Bd presence in amphibians?

Answer 12

Techniques include quantitative PCR for detecting Bd DNA and swabbing methods to collect samples from amphibians.

Question 13

What were the findings of the Bd surveillance in British Columbia?

Answer 13

Out of 955 animals swabbed, 150 tested positive for Bd, suggesting widespread distribution and potential transmission methods beyond introduced species.

Question 14

What genetic findings were associated with Bd?

Answer 14

Whole genome analysis revealed 51,915 SNPs among different Bd isolates, indicating low genetic diversity but multiple introduction events globally.

Question 15

What are the four major Bd lineages identified worldwide?

Answer 15

The Global Pandemic Lineage (BdGPL), Cape lineage (CAPE), Swiss lineage (CH), and the Asian lineage (BdASIA-1).

Question 16

How can biosecurity regulations help mitigate the spread of Bd?

Answer 16

Strengthening regulations can limit the movement of infected amphibians, requiring routine screenings in commercial frog farms and trade practices.

Question 17

What is the impact of Bd on biodiversity?

Answer 17

Bd has caused mass declines and extinctions in amphibian populations, disrupting ecosystems and leading to losses in biodiversity.

Question 18

Describe the lifecycle of Bd.

Answer 18

The lifecycle includes flagellated zoospores that colonize hosts, develop into thalli, form zoosporangia, and release new zoospores for dispersal.

Question 19

What is the ecological role of Chytridiomycota?

Answer 19

Chytridiomycota play significant roles as decomposers, parasites, and pathogens, impacting nutrient cycling and host populations in freshwater ecosystems.

Question 20

What is the significance of the Rhynie Chert in understanding Chytridiomycota?

Answer 20

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.

Question 21

What are the main modes of zoospore dispersal in Chytridiomycota?

Answer 21

Zoospores disperse primarily through swimming in soil moisture or water, using chemotaxis or possibly phototaxis to locate new substrates.

Question 22

How does the morphology of Chytridiomycota vary among different taxa?

Answer 22

Morphology can be holocarpic (single zoosporangium) or eucarpic (multiple structures), and can be monocentric (one zoosporangium) or polycentric (multiple zoosporangia).

Question 23

What are some key challenges in studying Chytridiomycota?

Answer 23

Challenges include their diverse lifestyles, incomplete understanding of their phylogeny, and the difficulties in culturing many species in the laboratory.

Question 24

Why are amphibians particularly vulnerable to Bd infections?a

Answer 24

amphibians have permeable skin that is crucial for respiration and hydration, making them more susceptible to pathogens that impair these functions.

Question 25

What evidence supports the idea that Bd is a novel pathogen?

Answer 25

Rapid mass mortalities in susceptible host populations, especially following the introduction of Bd to new areas, support the novel pathogen hypothesis.

Question 26

How do environmental conditions influence Bd’s pathogenicity?

Answer 26

Warmer temperatures (above 25°C) can reduce Bd’s virulence, while cooler conditions (4°C to 25°C) are optimal for its growth and pathogenic effects.

Question 27

What are the potential consequences of Bd on amphibian evolution?

Answer 27

Bd may lead to selective pressures that could drive evolutionary changes in amphibian populations, including shifts in resistance or susceptibility traits.

Question 28

How has Bd impacted conservation efforts for amphibians?

Answer 28

The emergence of Bd has necessitated increased monitoring, habitat protection, and research into amphibian resilience and management strategies to prevent further declines.

Question 29

What role do vectors like the American bullfrog play in the spread of Bd?

Answer 29

Vectors such as the American bullfrog can introduce and propagate Bd in new regions, often competing with and displacing native amphibian species.

Question 30

What strategies can be employed for Bd mitigation in amphibian populations?

Answer 30

Strategies include habitat restoration, captive breeding programs, enhanced biosecurity measures, and public awareness campaigns about the risks of amphibian trade.

Question 31

Describe the importance of molecular techniques in studying Bd.

Answer 31

Molecular techniques like quantitative PCR allow for sensitive detection of Bd DNA, enabling researchers to monitor its presence and spread in wild populations.

Question 32

How do different Bd lineages affect amphibian populations?

Answer 32

Different lineages of Bd exhibit varying levels of virulence, impacting susceptibility and mortality rates in amphibian species differently across geographic regions.

Question 33

What are the implications of Bd’s low genetic diversity?

Answer 33

Low genetic diversity in Bd suggests a limited adaptive capacity, which could affect its long-term survival and virulence potential, but also indicates a high risk for rapid spread.

Question 34

What are the ecological impacts of Bd-related amphibian declines?

Answer 34

Declines in amphibian populations can disrupt food webs, alter ecosystem dynamics, and reduce biodiversity, with cascading effects on other organisms and habitats.

Question 35

How is Bd transmitted between amphibians?

Answer 35

Bd can be transmitted directly through contact between infected and healthy amphibians or indirectly via contaminated water or substrates.