Crayfish Carrying Chytrid… What Next?

Crayfish

Crayfish have now been found to carry chytrid, potentially including this large crayfish species that is invasive in Virginia.

A study published late last year in the Proceedings of the National Academy of Sciences found that at least two different crayfish from different genera (Procambarus and Orconectes), both of which may be found in the United States, can carry the dreaded amphibian chytrid fungus. Crayfish from the genus Procambarus are found in both North and Central America, making their ability to carry Bd significant to amphibian conservation in both areas. The authors also tested mosquitofish, but fortunately the fish were not able to carry Bd.

During field surveys, the authors found that in Colorado wetlands, where the crayfish were infected with chytrid, so were the amphibians. Crayfish in streams and wetland habitats may serve as reservoirs for the disease if they do not die from Bd. Or perhaps they could be useful to determine the presence or absence of chytrid in an environment. More studies on the interactions between crayfish, Bd, amphibians, and their environmental reservoir are needed to fully understand the role that crayfish might play in disease transmission.

A second fascinating finding of the study that is worth mentioning was that exposure to water that had previously held Bd resulted in the deaths of crayfish. Exactly what this means is yet to be determined, but it suggests that the fungus might release chemicals that can cause negative effects on the host even when zoospores are not present. At this time, I am not sure whether amphibians would die from being exposed to water that once carried Bd. However, it is almost certain that Bd does produce some sort of chemicals that allow for the infection of an amphibian (or crayfish) host. Determining exactly what these chemicals are and what their function is may be important to understanding the mechanism behind Bd infection. Only time (and lots more research) will tell. This study has certainly brought several more intriguing questions to the study of chytridiomycosis disease dynamics.

Frog: 5, Fungus: 7

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