Population-Level Resistance to Chytridiomycosis is Life-Stage Dependent in an Imperiled Anuran

AbstractAmphibian declines caused by chytridiomycosis have been severe, but some susceptible populations have persisted or even recovered. Resistance to the causal agentBatrachochytrium dendrobatidis (Bd) could result from alleles of the adaptive immune system. During metamorphosis, however, immune systems may not be fully functional, implying that an effective immune response toBd may be life-stage dependent. We evaluated the susceptibility of the relict leopard frog (Rana onca) sourced from two areas whereBd was present or absent, and where the populations appeared to show differences in pathogen resistance. We evaluated whether population-level resistance manifested across life stages using challenge experiments with late-stage tadpoles (Gosner stage 31 –38), metamorphs (stage 45–46), and juvenile frogs. We used three differentBd isolates including one from wildR. onca to challenge juvenile frogs and focused on the isolate fromR. onca to challenge tadpoles and resulting metamorphs. We found that juveniles from theBd exposed population were 5.5 times more likely to surviveBd infection and 10 times more likely to clear infections than those from the area withoutBd. In contrast, and regardless of the source area, we observed 98% survivorship of tadpoles, but only 19% survivorship of resulting metamorphs following re-exposure. Given the low survivorship of exposed metamorphs in the laboratory, we speculate on how resistance characteristics, whether adaptive or innate, that...

Source: EcoHealth - October 24, 2019 Category: Environmental Health Source Type: research