03 February 2013

Chytridiomycosis in Rio: Serra dos Órgãos

Feb. 3, 2013. We've recently returned from a trip east to a national park called Serra dos Órgãos (PARNASO) in the state of Rio de Janeiro. This region of Brazil is particularly interesting because it is a place where a few endemic species have declined in recent times (Silvano and Segalla 2005), including the species Thoropa petropolitana. Whether or not chytridiomycosis is involved in the declines is something we hope to address with our research. Many things about PARNASO seem like a good place for Bd: it is a cloud forest, extremely wet with many streams, pools and rivers, cool temperatures, and proximity to a major metro area, the town of Teresópolis. Amphibian diversity is high here, including about 100 species, with some species like T. petropolitana and Aplastodiscus musicus only known from this location.


Bd group at PARNASO: L to R: Joice Ruggeri Gomes, Carlos Henrique Nunes-de-Almeida, Clarisse Betancourt-Roman, Thomas Jenkinson, Tim James

If there are chytridiomycosis related declines in Brazilian Atlantic Forest then this might be the place. Could all the environmental conditions be met such that chytrid can actually lead to species decline and even extinctions here unlike other parts of the AF where no disease related declines are known? And is this region a bubbling breeding ground for the formation of virulent strains of Bd that have been dispersed to parts far and wide and have caused havoc in other parts of the world. Is this the heart of the global chytridiomycosis epidemic?


Aplastodiscus is found in PARNASO in epiphytic bromeliads.

This leads me back to the discussion of whole reason why the Brazilian Atlantic Forest is so important for chytridiomycosis research. First, the biodiversity and endemism of the region is phenomenal, yet horribly threatened by anthropogenic disturbance. Second, the region has many threatened species and many species for which data are inadequate (see note by Pimenta et al. 2005), but those declines and disappearances are suspected of being due to habit destruction with no known role for chytrid. Yet, when you look at the models that attempt to predict the distribution of chytrid based on existing data and climate/species variables, they strongly suggest that chytridiomycosis should be very prevalent throughout the AF, with some non-negligible risk of decline or distinction centered around Rio de Janeiro (see Figure C below from Rödder et al.2009, Diversity 1:52). These models are entirely consistent with the existing publications showing chytrid to be widespread in the AF (Carnaval et al. 2006, EcoHealth 3:41; Toledo et al. 2006, South American Journal of Herpetology 1:185) and our own observations from this trip. Yet based on the analysis of Bielby et al. (2008, Con. Letters 1: 82), many of the life history characteristics of species declining due to Bd in other geographic regions are not observed in the AF. The details of this analysis regarding amphibians of the AF are a little curious to me, as Bielby et al. identified high altitude, low fecundity, and aquatic life history traits as factors associated with risk of species displaying Bd-associated declines, and all of these characterize at least parts of the AF herpetofauna. Something also is a bit imperfect in the models as Panama doesn't show a smoking signal in the models, yet it is the most notorious region of Bd declines.


Figure 2 of Rödder et al. 2009. A). Species Distribution Model showing the potential distribution of Bd based on existing occurrence data and climate variables. B). Overlap of the potential Bd distribution and amphibian diversity shows the Brazilian Atlantic Forest to have the huge potential for species declines and possibly Bd diversity. C). However, Risk Factor analysis suggests that by overlaying potential Bd distribution and life history traits of the animals, the Atlantic Forest amphibians are not nearly in as much jeopardy as Andean frogs.

Just as expected, we found evidence for Bd in PARNASO on from infected tadpoles collected from streams. We also swabbed exactly 100 adults for later molecular diagnostic tests for Bd that will be done at UNICAMP. Adults were a bit hard to find, which our local expert, Joice Ruggeri, suggested was due to the incessant rain rather than chytridiomycosis, based on her experiences at PARNASO. We are currently working on isolation of the pathogen from the tadpoles and are ultimately very interested in determining the genotypes of the Bd strains. Our hypothesis is that PARNASO may show an epidemic population structure with a single genotype of the hyper-virulent Bd-GPL group.

I wanted to share some excellent photos that Clarisse Betancourt-Roman took of the infected tadpole mouthparts. These poor tads can get so infected by Bd, that their foraging behavior is significantly reduced (Venesky et al. 2009).

Figure A) the upper jawsheath is clear and black across, whereas in B) most of the pigment of the upper jawsheath (red arrow) is missing. C) another jawsheath shows a large region of depigmentation in the center (arrow). D). Under higher magnification, numerous spheroid Bd sporangia can be seen. credit (Clarisse Betancourt-Roman).

PARNASO also has tons of amazing wildlife, plants, and fungi.




Brachycephalus ephippium (sapinho-pingo-de-ouro or pumpkin toadlet). B. ephippium moves very slowly but it can afford to because its color is a warning that it is highly poisonous. However, it can also leap when needed and does an odd karate kid style move when threatened by other males.



Marasmius


Favolaschia




fruit flies aggregating on the surface of a Ganoderma mushroom


rufous-crowned greenlet (credit Carlos Henrique Nunes-de-Almeida)


pin-tailed manakin (credit Carlos Henrique Nunes-de-Almeida)

These last two pictures were taken by Carlos Henrique who is a graduate student with Felipe Toledo and also an amazing birder who leads tours in southern Brazil (http://www.carduelis.bio.br/).

Falamos depois!