Wednesday, 28 September 2011

Amphibian immunity is associated with resistance to Bd

Savage and Zamudio report in PNAS that survival following infection by Bd is associated with major histocompatability genotype. Two of the five experimental infected populations of lowland leopard frogs (Lithobates yavapaiensis) had significantly elevated survival. This survival was associated with alleles at MHC class IIB and heterozygosity at the locus (see figure). This observation likely has wider significance; for instance Tobler and Schmidt have demonstrated among-population variation in survival for Swiss populations of midwives Alytes obstetricans (PLoS One). Therefore, Evolutionary Conservation, by breeding for resistance, is increasingly looking like a viable tool to combat chytridiomycosis. The hunt is on!

High Prevalence of Bd in Gabon

Bell et al  have reported in Ecohealth a high prevalence of Bd from two national parks in Gabon, Monts de Cristal and Ivindo. Bd was detected in 20 of the 42 species and was present at all three sites surveyed with high prevalence (19.6%–36.0%). Both national parks were Bd-positive at all elevations and across habitat types, though no dead or dying frogs were encountered. This last observation is in keeping with those made in other regions of Africa, barring dieoffs reported from Kihansi and the Drakensburg. Bell et al's report contrasts with those of Gratwick et al who sampled other regions of Gabon: all were negative. Therefore, there appears to be a high degree of spatial heterogeneity in the prevalence of Bd in Gabon which begs the question, Why?