Análisis ecotoxicológico de una comunidad de anuros de la Región Pampeana : Efecto del Cr[VI] sobre embriones y larvas de distintas especies de una taxocomunidad

Tesis presentada para optar al Grado de Doctor en Ciencias NaturalesFil: Natale, Guillermo Sebastián. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentin

The tadpole of <i>Physalaemus fernandezae</i> (Anura: Leptodactylidae)

This paper describes the external and buccopharyngeal morphology, chondrocranium and cranial muscles in tadpoles of Physalaemus fernandezae. The data are compared with those for other species of Physalaemus to improve the diagnosis of the “species group” within the genus. Species of the “P. biligonigerus” group have four infralabial papillae, two semicircular arches of pustulations in a V-shaped pattern on the prenarial arena, 6–8 conical papillae and 40–60 pustulations on the buccal roof arena, four postnarial papillae, a semicircular median ridge, clawshaped lateral ridges and larval crista parotica with a poorly-developed anterior process. Species of the “P. pustulosus” group possess four infralabial papillae (shared with the P. biligonigerus group), tooth row formula 2(2)/3, four lingual papillae, two postnarial papillae, twelve conical papillae and 16–20 pustulations on the buccal roof arena, short lateral ridges with rough concave margins and larval crista parotica with a well-developed anterior process and reduced posterior process. Species of the “P. cuvieri ” group present two infralabial papillae, three pustulations and two serrated papillae on the prenarial arena, five pustulations and two serrated papillae on the postnarial arena, four long and bifid papillae and more than 60 pustulations on the buccal roof arena, and lack larval crista parotica. In species of the “P. signiferus” group both medial and lateral mental gaps are absent, and the tooth row formula is 2(2)/3(1).Instituto de Limnología "Dr. Raúl A. Ringuelet"Centro de Investigaciones del Medioambient

Chytrid fungus parasitizing the wild amphibian Leptodactylus ocellatus (Anura: Leptodactylidae) in Argentina

The present contribution is the first report of parasitosis by a chytrid fungus in wild anuran amphibians in Argentina, as well as the first case of amphibian mortality documented to date in Argentina. We report the presence of the chytrid fungus in dead adult Leptodactylus ocellatus. It has been suggested that chytridiomycosis is the main cause of death in several amphibian populations worldwide. Our study demonstrates that chytridiomycosis afflicts L. ocellatus, a common widespread amphibian species, and is the first report of chytridiomycosis in the Argentinian lowlands. The occurrence at this latitude would indicate an extended distribution of this fungus in wildlife populations. It is also the first report of amphibian mortality due to chytrid fungus in our country. It is noteworthy that the site of collection is situated very close to sea level in a temperate climate zone and that this represents the southernmost record for South American wild amphibians.Instituto de Botánica "Dr. Carlos Spegazzini"Facultad de Ciencias Naturales y MuseoCentro de Investigaciones del Medio Ambient

Chytrid fungus parasitizing the wild amphibian Leptodactylus ocellatus (Anura: Leptodactylidae) in Argentina

The present contribution is the first report of parasitosis by a chytrid fungus in wild anuran amphibians in Argentina, as well as the first case of amphibian mortality documented to date in Argentina. We report the presence of the chytrid fungus in dead adult Leptodactylus ocellatus. It has been suggested that chytridiomycosis is the main cause of death in several amphibian populations worldwide. Our study demonstrates that chytridiomycosis afflicts L. ocellatus, a common widespread amphibian species, and is the first report of chytridiomycosis in the Argentinian lowlands. The occurrence at this latitude would indicate an extended distribution of this fungus in wildlife populations. It is also the first report of amphibian mortality due to chytrid fungus in our country. It is noteworthy that the site of collection is situated very close to sea level in a temperate climate zone and that this represents the southernmost record for South American wild amphibians.Instituto de Botánica "Dr. Carlos Spegazzini"Facultad de Ciencias Naturales y MuseoCentro de Investigaciones del Medio Ambient

Amphibia, Anura, Leiuperidae, Pleurodema bibroni: Rediscovery

The genus Pleurodema Tschudi, 1838 consists of thirteen species distributed along southern South America (Frost 2007). Among these, Pleurodema bibroni inhabits Uruguay and southern Brazil (Achaval and Olmos 2003; Machado and Maltchik 2007). Although the systematics of P. bibroni was largely studied in the last century (Barrio and Rinaldi di Chieri 1970; Barrio 1977), it is one of the least known species amongst the amphibian fauna of Uruguay. In spite of this, this species was very common in the Uruguayan coast in the past (Langone, in press) and one observational record was published in recent times (Maneyro et al. 1995), the last specimens stored in scientific collections were collected in 1982. Based on these data, the species is considered as endangered at the national scale in Uruguay (Maneyro and Langone 2001; Canavero et al. 2004), while it is classified as Near Threatened (NT) at the global level (IUCN et al. 2006). The aim of this work is to report a recent record of P. bibroni in southeastern Uruguay.Centro de Investigaciones del Medioambient

Acute and chronic effects of Cr(VI) on Hypsiboas pulchellus embryos and tadpoles

In the last few years there has been great concern about declines in the abundance of several species of amphibians around the world. Among amphibians, anurans have a biphasic life cycle, with aquatic tadpoles and generally terrestrial adults, and they have an extremely permeable skin, making them excellent indicators of the health of the environment. A number of different causes have been suggested for the global decline of anurans, the pollution of their habitat by chemical stressors being considered one of the major factors. Among chemical stressors, heavy metals are known for their high toxicity at very low concentrations. This study assessed short- (96 h, 'acute') and long-term (1272 h, 'chronic') exposure to Cr(VI) at lethal (3 to 90 mg l-1) and sublethal concentrations (0.001 to 12 mg l-1) on Hypsiboas pulchellus (previously called Hyla pulchella; see Faivovich et al. 2005) tadpoles (Fam. Hylidae) from central eastern Argentina. Fertilized eggs collected from a clean pond near La Plata (Buenos Aires Province) were used for acute and chronic toxicity testing. Assays were done under controlled laboratory conditions. Results of chronic exposure were used to assess the effect of factors such as toxicant concentration and age of organisms at the beginning of exposure on the response variables (growth, development and survival until metamorphosis). Results indicated a higher sensitivity to Cr(VI) of individuals first exposed as tadpoles than those first exposed as embryos during acute and chronic exposure. Exposure to the highest sublethal concentrations (6 to 12 mg l-1) of the toxicant showed early inhibitory effects on growth of all treated organisms compensated at longer exposure periods with an increase in the growth rate compared to the control groups.Centro de Investigaciones del Medio Ambient

First Record of Batrachochytrium dendrobatidis in Physalaemus fernandezae (Anura: Leiuperidae) for Buenos Aires province, Argentina

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 Physalae-mus fernandezae, from Punta Lara Natural Reserve (34.8033 ̊S, 58.0099 ̊W), Ensenada, Buenos Aires province, Argentina.Centro de Investigaciones del Medioambient

Chytrid fungus parasitizing the wild amphibian Leptodactylus ocellatus (Anura: Leptodactylidae) in Argentina

The present contribution is the first report of parasitosis by a chytrid fungus in wild anuran amphibians in Argentina, as well as the first case of amphibian mortality documented to date in Argentina. We report the presence of the chytrid fungus in dead adult Leptodactylus ocellatus. It has been suggested that chytridiomycosis is the main cause of death in several amphibian populations worldwide. Our study demonstrates that chytridiomycosis afflicts L. ocellatus, a common widespread amphibian species, and is the first report of chytridiomycosis in the Argentinian lowlands. The occurrence at this latitude would indicate an extended distribution of this fungus in wildlife populations. It is also the first report of amphibian mortality due to chytrid fungus in our country. It is noteworthy that the site of collection is situated very close to sea level in a temperate climate zone and that this represents the southernmost record for South American wild amphibians.Instituto de Botánica "Dr. Carlos Spegazzini"Facultad de Ciencias Naturales y MuseoCentro de Investigaciones del Medio Ambient

“Mohos zoospóricos” (Saprolegniales, Peronosporomycetes) causantes de oomicosis en huevos de anfibios: estudio preliminar de los principales géneros involucrados

Los mohos acuáticos zoospóricos (Saprolegniales, Peronosporomycetes) son organismos saprótrofos ubicuos, parásitos de anfibios (huevos, juveniles, adultos) y de otros integrantes de la cadena trófica en ambientes acuáticos. Se analizaron y procesaron muestras de agua, materia orgánica y huevos de Rhinella arenarum mediante técnica de cebado, colectadas en un ecosistema acuático temporario del Pdo. La Plata (Bs. As., Argentina). Cinco géneros de organismos parásitos de huevos fueron registrados: Achlya, Brevilegnia, Pythiopsis, Saprolegnia y Thraustotheca, siendo Pythiopsis el género que más frecuentemente colonizó sustratos colocados en cajas de Petri analizadas. Se citan por primera vez en el país a los géneros Brevilegnia, Pythiopsis y Thraustotheca como parásitos de huevos de anfibios autóctonos. Las especies serán determinadas a posteriori por técnicas morfológicas y moleculares.Centro de Investigaciones del MedioambienteInstituto de Botánica "Dr. Carlos Spegazzini

Acute and chronic effects of Cr(VI) on <i>Hypsiboas pulchellus</i> embryos and tadpoles

In the last few years there has been great concern about declines in the abundance of several species of amphibians around the world. Among amphibians, anurans have a biphasic life cycle, with aquatic tadpoles and generally terrestrial adults, and they have an extremely permeable skin, making them excellent indicators of the health of the environment. A number of different causes have been suggested for the global decline of anurans, the pollution of their habitat by chemical stressors being considered one of the major factors. Among chemical stressors, heavy metals are known for their high toxicity at very low concentrations. This study assessed short- (96 h, 'acute') and long-term (1272 h, 'chronic') exposure to Cr(VI) at lethal (3 to 90 mg l-1) and sublethal concentrations (0.001 to 12 mg l-1) on Hypsiboas pulchellus (previously called Hyla pulchella; see Faivovich et al. 2005) tadpoles (Fam. Hylidae) from central eastern Argentina. Fertilized eggs collected from a clean pond near La Plata (Buenos Aires Province) were used for acute and chronic toxicity testing. Assays were done under controlled laboratory conditions. Results of chronic exposure were used to assess the effect of factors such as toxicant concentration and age of organisms at the beginning of exposure on the response variables (growth, development and survival until metamorphosis). Results indicated a higher sensitivity to Cr(VI) of individuals first exposed as tadpoles than those first exposed as embryos during acute and chronic exposure. Exposure to the highest sublethal concentrations (6 to 12 mg l-1) of the toxicant showed early inhibitory effects on growth of all treated organisms compensated at longer exposure periods with an increase in the growth rate compared to the control groups.Centro de Investigaciones del Medioambient