The effect of captivity on the skin microbiota of three lowland Atelopus species

Background/Question/Methods

Epidemic diseases often lead to dramatic declines in specific taxa. To understand the dynamics of epidemic diseases, surviving individuals often represent the only available source of information. We know that microbial communities present in amphibian skin play an important protective role against the pathogenic fungus Batrachochytrium dendrobatidis (Bd). Species-specific differences in skin bacterial communities explain concomitant differences in vulnerability to Bd. However, almost nothing is known about the origin and dynamics of microbial communities. In particular, we do not know whether amphibians kept in captivity for conservation purposes change their cutaneous microbiota perhaps affecting the chances of successful reintroduction programs. In this study we (1) estimated the diversity of bacteria assemblages in three species of Atelopus before and after entering a ex situ conservation program, (2) described the effect of captivity on the skin microbiota diversity and (3) identified culturable bacteria with anti-Bd activity to be considered as candidates to be used in probiotic therapy. We took and cultured bacterial samples of Atelopus spurrelli, A. aff. limosus and A. elegans from individuals in the wild and in captive conditions at Cali Zoo and Balsa de los Sapos. We then compared anti-Bd activity, as inferred from antagonism assays, between wild and “captivity” strains.

Results/Conclusions

We isolated 341 morphotypes of 46 toads, 188 from the wild (N = 25 frogs) and 153 obtained from individuals who are part of the ex situ conservation programs (N = 21). In total 102 morphotypes inhibited Bd growth. Morphotypes were identified by sequencing the 16S ribosomal gene. We identified 73 species of bacteria, of these, only 28 species exhibited antifungal activity. We found that (1) captivity did not lead to appreciable reduction in skin bacteria diversity, (2) frogs in captivity still harbor bacteria with anti-Bd activity, (3) wild microbiota did not differ from “captivity” microbiota in anti-Bd activity, although (4) there was higher among-strains variance in the former group. Our results suggest that captivity programs do not necessarily change bacterial communities of the toad skins in a way that impedes Bd growth control and eventual reintroduction.