Amphibian species vary in their learned avoidance response to the deadly
fungal pathogen Batrachochytrium dendrobatidis
Abstract
Abstract: Lethal and sublethal effects of pathogens should theoretically
select for host avoidance of these organisms. Oak toads, for example,
learn to avoid the pathogenic fungus Batrachochytrium dendrobatidis (Bd)
after one infection-clearance event. Here, we investigated whether four
taxonomically distinct amphibians, Cuban treefrogs (Osteopilus
septentrionalis), southern toads (Bufo terrestris), greenhouse frogs
(Eleutherodactylus planirostris), and pine woods treefrogs (Hyla
femoralis) were also able to learn to avoid Bd and, if so, what cues
they used to identify Bd. Cuban treefrogs, pine woods treefrogs, and
greenhouse frogs did not appear to exhibit detectable innate or learned
avoidance of Bd. However, southern toads learned to avoid Bd after only
one exposure. Southern toads avoided any treatment containing Bd
metabolites but did not avoid treatments that lacked Bd metabolites even
when dead zoospores were present. Bd metabolites include digestive
enzymes that breakdown host tissue and appear to be the cues that
amphibians use to avoid Bd, which is consistent with a Classical or
Pavlovian Conditioning response. It appears that not all species respond
the same way to Bd, which is important information when developing
disease models and conservation plans for amphibians.