Batrachochytrium dendrobatidis (Bd) is a contagious pathogenic fungus that has caused amphibian decline worldwide. This is a well-studied species but little is known about the differences in fungal morphology among the Bd strains. Here, we compared the morphology of two virulent strains of Bd, one isolated from amphibians in California and the other from Panama. The two strains were imaged using a scanning electron microscope and we compared the diameter of infectious zoospores, the diameter of the zoosporangia, and the number and size of zoospore discharge tubules found on the zoosporangia. We also grew both strains in culture and examined zoospore and zoosporangia production over time.
We found that the Panama zoospores and zoosporangia were larger in diameter (p < 0.0001, for both) and had more discharge tubules per zoosporangium compared to the California strain. There were no differences between the strains in respect to the size of the discharge tubules. We also found that the strains differed in zoospore, but not zoosporangia, production in culture (p = 0.0002 and p = 0.6, respectively). Therefore, the Panama strain may be able to grow faster, potentially altering pathogen virulence. Bd is found globally and in laboratory experiments infections are often compared to one another, this morphology and growth information helps us better understand infection dynamics and strain virulence.