First record of Batrachochytrium dendrobatidis in Physalaemus fernandezae (ANURA: LEIUPERIDAE) for Buenos Aires Province, Argentina

DELGADO C.S.; NATALE G.S.; HERRERA R.H.; BARRASSO D.A.

HERPETOLOGICAL REVIEW

SSAR

Año: 2012 vol. 43 p. 84 - 85

0018-084X

In Argentina, Batrachochytrium dendrobatidis (Bd) is known from Buenos Aires, Córdoba, Misiones, Neuquén, San Luis, Salta, and Tucumán provinces (Arellano et al. 2009; Barrionuevo and Mangione 2006; Fox et al. 2006; Ghirardi et al. 2009; Gutierrez et al. 2010; Herrera et al. 2005). We provide the first record of Bd infection in a population of the pond-breeding anuran Physalaemus fernandezae, from Punta Lara Natural Reserve (34.8033ºS, 58.0099ºW), Ensenada, Buenos Aires province, Argentina. Punta Lara Natural Reserve is located on the western bank of Río de La Plata. It has a warm-temperate climate with a mean annual temperature of 16ºC (-4ºC minimum; 42ºC maximum), and has a few days with frost, mostly in June and July. Annual precipitation is slightly over 1000 mm (SMN 2011). Physalaemus fernandezae is distributed in Buenos Aires and Entre Ríos provinces, Argentina, and some localities from southern Uruguay (Barrio 1964). It reproduces mainly in marshy grasslands with two reproductive events per year (Barrio op. cit.). The dominant breeding season takes places between May and August (colder temperature months), but may extend until December, in many cases overlapping reproductive events with others sympatric anurans: e.g., Hypsiboas pulchellus, Odontophrynus americanus, and Scinax squalirostris. The second reproductive event involves fewer animals and takes place approximately between February to March, coinciding with reproduction activities of Dendrosophus nanus, D. sanborni, Hypsiboas pulchellus, Pseudopaludicola falcipes, Pseudis minuta, Scinax squalirostris, S. berthae, and S. granulatus. Currently, P. fernandezae has an IUCN conservation status of Minor Concern (IUCN 2011). Seven adult specimens of P. fernandezae were collected at Punta Lara Natural Reserve in September 2007, preserved in 10% formalin and deposited in the herpetological collection of Museo de La Plata (MLP-A. 5385-5391). A skin sample (length: 5 mm; width: 2 mm) was taken from the ventral zone of selected specimens, immersed in paraffin, thin-sectioned every 5 µm with a microtome (Leica, RM 2125 RT), mounted onto a microscopic slide and stained with haematoxilin and eosin, after Drury and Wallington (1980). Histological slides were analyzed for Bd following procedures described in Berger et al. (1999), with a binocular microscope (Olympus Optical Co. Ltd., Tokyo, Japan; model BX 50). Diagnostic images were taken with an Olympus DP 71 digital camera mounted to the scope. The presence of Bd was confirmed for 3 of 7 (42.85%) skin samples analyzed. Different developmental stages of chytridiomycosis were clearly visible, namely: zoosporangia (isolated and grouped), empty and containing zoospores (Fig. 1), diagnostic characteristics such as a septum and discharge tube (Fig. 2), and hyperplasic epidermis. It is worth mentioning that the population of P. fernandezae used in this study, has been studied by local herpetologists since 2001, but no moribund or dead specimens have been recorded to date. Moreover, the individuals in which infection was detected had been engaged in reproductive activities.