INVESTIGADORES
LONGO Maria Silvana
artículos
Título:
Batrachochytrium dendrobatidis in Argentina: first record in Leptodatylus gracilis and another record in Leptodactylus ocellatus.
Autor/es:
GHIRARDI, R.; LESCANO, J. N.; LONGO, M. S.; ROBLEDO, G.; STECIOW, M. M.; PEROTTI, M. G.
Revista:
HERPETOLOGICAL REVIEW
Editorial:
Society for the Study of Amphibians and Reptiles
Referencias:
Año: 2009 vol. 40 p. 175 - 176
ISSN:
0018-084X
Resumen:
In the last few decades, rapid declines and extinctions of populations
have been reported in more than 400 amphibian species all
over the world. A pathogen that has received attention relative to
these losses is the chytridiomycete Batrachochytrium dendrobatidis
(Bd). Ron (2005) identified potentially suitable regions for Bd
establishment in the New World. In South America, Ron predicted
suitable regions included the Brazilian Atlantic forest, the temperate
forest in Chile and western Argentina (south to 30ºS), northeastern
Argentina, Uruguay, and Paraguay. Thus far in Argentina,
Bd has been reported in four anuran species at three geographic
locations: 1) Barrionuevo and Mangione (2006) found Bd in Telmatobius
pisanoi and T. atacamensis (Anura: Leptodactylidae)
in mountainous areas of Northern Argentina; 2) Arellano et al.
(2006) and Herrera et al. (2005) reported Bd in adult specimens of
Leptodactylus ocellatus (Anura: Leptodactilidae) in Buenos Aires
province; and 3) in North Patagonia, Fox et al. (2006) found Bd in
Atelognathus patagonicus (Anura: Leptodactilidae). We present
Bd detections in central Argentina: a new occurrence in the Striped
Thin-toed Frog (Leptodactylus gracilis) and another occurrence in
the Spotted Thin-toed Frog (Leptodactylus ocellatus).
Dead specimens of the two leptodactilids were found during
field surveys and were deposited in the collection of Centro de
Zoologia Aplicada (Universidad Nacional de Córdoba, Argentina).
A specimen of Leptodactylus ocellatus (CZA a-00011) was collected
on May 2005 (31.3967ºS, 64.5936ºW) and a specimen of Leptodactylus gracilis (CZA a-00010) was collected on March
2006 (31.3855ºS, 64.6057ºW), on the banks of the Toro Muerto
stream, in the locality of Villa Flor Serrana, in a mountainous area
of Córdoba province, Central Argentina, at 800 m elevation. The
stream had a mean depth of 70 cm and flowed intermittently over
granitic rock. The physiognomy of the surrounding vegetation was
that of serrano secondary forest and thorny shrublands, typical of
the Chacoan region (Cabrera 1976). Annual rainfall is 950 mm
and is mainly concentrated in spring and summer. Mean annual
temperature is 18.9°C, ranging from peak values in summer that
may exceed 38°C to winter frosts (Capitanelli 1979).
The specimens were fixed in the field in 10% neutral formaldehyde
solution and then were transferred to 70% ethanol. In the
laboratory, abdominal and hind limb ventral skin patches (~5 x 10
mm) were excised from the anurans, stored in 70% ethanol and
dehydrated to embed in paraffin. Then, tissues were sectioned at 5-
μm thickness with a Reitcher microtome for histology, and stained
with hematoxylin & eosin. With a stereomicroscope, we looked
for spores and sporangia in the corneous epithelium of the tissue
samples following Berger et al. (1999) and Pessier et al. (1999).
We identified Bd in the two specimens analyzed. Zoosporangia
at different developmental stages, empty or containing rounded
basophilic zoospores, were identified in the stratum corneum.
With those results, we increase the geographic distribution of Bd
in Leptodactylus ocellatus, and report the first record of infection
in L. gracilis. These two species are widespread in a broad region
of Argentina, supporting the need to conduct further studies of
Bd to investigate the status of these populations and the risk to
sympatric species. The first case of Bd in Argentina was detected
in 2002 in a dead specimen (Herrera et al. 2005), and until now
eleven specimens (include our two) belonging to five different species
have been found infected (Arellano et al. 2006, Barrionuevo
and Mangione 2006, Fox et al. 2006, Herrera et al. 2005). Our
finding expands the known distribution of Bd to the wilderness
area of the Chacoan phytogeographic region of Argentina, Chaco
Serrano district (Cabrera 1976) (Fig. 1). Although Rons (2005)
prediction map of potentially suitable regions for Bd establishment infections detection, these prediction have been made on the bases
of only 44 points over the New World, and none of these points was
either from Argentina or neighboring countries, resulting in a low
precision. Further information is needed about the prevalence and
habitat requirements of Bd infecting anurans inhabiting Argentina
for modeling an actualized and more precise Bd distribution map.
An increase in the number of amphibian species monitored will
help us to estimate the health of wild populations. The collection
of environmental and biological data will provide us with valuable
tools to predict new scenarios and implement adequate and
specific conservation policies in order to manage disease outbreaks
in Argentina.