RESUMEN
The skin of anuran amphibians is a rich source of compounds with great medicinal potential. Alzheimer's disease (AD) is a complex disease associated with numerous pathological pathways, making their simultaneous modulation necessary. Nowadays the development of anti-AD drugs is focused on a Multi-Target Directed Ligands strategy. Herein we report the bioactivity of the skin extracts of the toad Rhinella arenarum obtained by an invasive and non-invasive methods, against five AD pathological targets (AChE, BChE, MAO-B, antioxidant and chelating activities). The extract derived from the non-invasive technique showed the highest biological activity, being capable of acting on all or almost all the pathological targets of AD, while also avoiding harm to the animal.
Asunto(s)
Enfermedad de Alzheimer , Enfermedad de Alzheimer/tratamiento farmacológico , Enfermedad de Alzheimer/metabolismo , Animales , Antioxidantes/farmacología , Inhibidores de la Colinesterasa/farmacología , Ligandos , Monoaminooxidasa/metabolismo , Inhibidores de la MonoaminooxidasaRESUMEN
Dimethoate (D) are among the most commonly used organophosphates insecticides in the world. To evaluate the toxicity of two D formulations were selected as test organisms tadpoles of Rhinella arenarum. This toad species has an extensive neotropical distribution and is easy to handle and acclimate to laboratory conditions. The tadpoles were exposed in an acute assay for 48 h to D soluble concentrates (DSC) and emulsifiable concentrates (DEC). The 48 h-LC50 (95% confidence limits) value of DSC was 57.46 mg L-1 (40.52-81.43) and to DEC was 12.76 mg L-1 (10.39-15.68). These differences in toxicity were statistically significant (p < 0.05). In both formulations, acetylcholinesterase), carboxylesterase, and glutathione-S-transferases enzyme activities varied significantly respect to those of control group (p < 0.05). The DEC formulation was the most toxic. These results would allow the assessment and characterization of potential ecological risks following the application of those formulations.
Asunto(s)
Bufo arenarum , Dimetoato/toxicidad , Insecticidas/toxicidad , Larva/efectos de los fármacos , Contaminantes Químicos del Agua/toxicidad , Acetilcolinesterasa/metabolismo , Animales , Dimetoato/química , Insecticidas/química , Larva/enzimología , Dosificación Letal Mediana , Pruebas de Toxicidad , Contaminantes Químicos del Agua/químicaRESUMEN
Agricultural activity, especially the increasing use of pesticides, is considered one of the main reasons for the decline of amphibian populations. Mancozeb (MCZ) is one of the most used fungicides worldwide, despite its ancient use and toxicity demonstrated in different taxa. However, there is limited information about the effects of MCZ in amphibians, which are keystones of riparian ecosystems. For species conservation purposes, it is essential to identify the most sensitive developmental period(s) of a given species to a xenobiotic. We evaluated the toxicity of a commercial fungicide of mancozeb, (80% active ingredient) on the early development of the common South American toad Rhinella arenarum (Anura, Bufonidae). Embryos from early blastula (S.4) and larvae from complete operculum (S.25) stages were exposed to a wide range of MCZ concentrations during acute, subchronic and chronic exposure (up to 504 h) periods. The toxicity profiles for lethal and sublethal effects were performed. At all exposure times, MCZ was more toxic to embryos, for instance, NOEC 504 h were 0.01 and 0.05 mg MCZ/L for embryos and larvae, respectively. Thus, embryo sensitivity was 5-fold higher than larvae. A Teratogenic Index of 14 indicated the significant teratogenic potential of this fungicide. Among sublethal effects, embryos exhibited a wide range of abnormalities with high incidence. The ecological risk assessment demonstrated that the estimated Risk Quotient value for Rhinella arenarum embryos at chronic exposure was higher than the Level of Concern value, which warns about the potential risk of MCZ for this native species.
Asunto(s)
Bufo bufo , Fungicidas Industriales/toxicidad , Maneb/toxicidad , Zineb/toxicidad , Animales , Bufo arenarum , Bufonidae , Ecosistema , Embrión no Mamífero , Larva , Medición de RiesgoRESUMEN
Changes in toxicity of As(V) solutions from acute to chronic exposure have been evaluated by the AMPHITOX test. This test employs Rhinella arenarum, a widely distributed toad in Argentine areas. LOEC values were 6.37 and 1.88â¯mg L-1 for embryos and larvae, respectively, and serious sublethal effects have been observed. Toxicity of As(V) solutions has been also evaluated after treatment with zerovalent iron nanoparticles (nZVI). After 60â¯min of treatment with nZVI, As(V) removal was 77%, and neither lethal nor sublethal effects were observed. However, nZVI had to be eliminated before the bioassay because they caused adverse effects in both embryos and larvae. This work highlights the high sensitivity of R. arenarum to As(V), the relevance to assess toxicity on different periods of the lifecycle, and the need to expand exposure to As(V) to chronic times. The utility of the test for monitoring toxicity changes in As(V) solutions after nZVI treatment has been also shown.
Asunto(s)
Arsénico/toxicidad , Bufo arenarum/crecimiento & desarrollo , Hierro/farmacología , Pruebas de Toxicidad/métodos , Animales , Embrión no Mamífero/efectos de los fármacos , Larva/efectos de los fármacos , Larva/crecimiento & desarrollo , Estadios del Ciclo de Vida/efectos de los fármacos , Nanopartículas , Contaminantes Químicos del Agua/toxicidadRESUMEN
In many amphibians, the granular glands can be grouped in special regions forming macroglands. This is the case of toads, characterized by the presence of a pair of parotoid macroglands, strategically located to give protection by poison release in case of attacks. The product secreted consists of a wide variety of chemical compounds including proteins, peptides, biogenic amines, toxic steroidal bufadienolides, and various alkaloids, depending on the species. In this work, using Rhinella arenarum, we have performed, for the first time, the matrix assisted-ultraviolet laser desorption/ionization mass spectrometry and tandem mass spectrometry characterization of the components of the secretion used as crude material, just suspended in MeOH (or MeCN). The crude sample as a whole (whole suspension) was spotted on the matrix assisted-ultraviolet laser desorption plate for analysis. Electrospray ionization-Orbitrap was used for cross-checking experiments. The pattern of signals obtained at m/z ranges 600 to 800 and 1200 to 1600 could be assigned as the argininyl bufadienolide esters fingerprint characteristic of female and male. Variation patterns for gender (female, male), age (non-reproductive, reproductive), and season (non-reproductive, reproductive) are described.
Asunto(s)
Arginina/análogos & derivados , Arginina/análisis , Bufanólidos/análisis , Cordados/fisiología , Glándula Parótida/metabolismo , Animales , Arginina/metabolismo , Bufanólidos/metabolismo , Cordados/crecimiento & desarrollo , Cromatografía Líquida de Alta Presión/métodos , Ésteres/análisis , Ésteres/metabolismo , Femenino , Masculino , Análisis de Componente Principal/métodos , Estaciones del Año , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Espectrometría de Masas en Tándem/métodosRESUMEN
Chlorpyrifos (CPF) is a broad spectrum pesticide commonly used for insect control, has great affinity for lipids and is thus a potential for bioaccumulation in aquatic organisms. The aim of this study was to evaluate the toxicity of CPF using the common toad Rhinella arenarum via dermal uptake in plastic bucket to simulate their natural exposition in ponds. R. arenarum toads were exposed individually to solutions containing a nominal concentration of a commercial formulation of CPF insecticide (5 and 10 mg/L). Different enzyme biomarkers (BChE: butyrylcholinesterase, CbE: carboxylesterase, and CAT: catalase) were measured in blood tissue after exposition. The capacity of pyridine-2-aldoxime methochloride (2-PAM) to reverse OP-inhibited plasma BChE and the ratio of heterophils and lymphocytes (H/L) as hematological indicators of stress were also determined. The normal values of plasma B-sterases (BChE and CbE) were highly inhibited (until ≈ 70%) in toads 48 h after exposure to CPF. The results indicate that 2-PAM produced BChE reactivation as well. The activity of CAT was also inducted for dermal exposure at more than double of that in the control toads (CPF; 5 mg/L). H/L ratios did not reveal a significantly increased stress. The study suggests that CPF via dermal uptake induced neurotoxicity and oxidative stress in the common toad R. areanum. Thus, some blood biomarkers employed in our study (i.e. BChE, CbE, 2-PAM, and CAT) might be used as predictors in health and ecological risk assessment of amphibian populations exposed to CPF.
RESUMEN
Four populations of Rhinella arenarum from aquatic environments with different degrees of disturbance in central Argentina were compared to assess the ability of cytomorphology and cytomorphometry of blood cells as a hematological biomarker. A total of 93 specimens of R. arenarum (adults sexually mature) were captured during the spring. From the analysis of cell, no variations were found in terms of morphology, whereas in nuclear and cell areas and Price-Jones curves, we observed a smaller size in erythrocytes of individuals inhabiting the site most altered, "Villa Dalcar," as well as for leukocytes, lymphocytes, neutrophils, and eosinophils for the same site. This could be caused by presence of different pollutants in the lake. Furthermore, this was confirmed by the high levels of environmental variables (conductivity, total dissolved solids, and salinity) show that Villa Dalcar is the site most affected by human activities.
Asunto(s)
Núcleo Celular/fisiología , Eritrocitos/citología , Animales , Argentina , Bufo arenarum , Núcleo Celular/química , Ecosistema , Salud Ambiental , LarvaRESUMEN
Little attention has been paid to the impact of wastewater generated by mining activities on fluoride. In this study, we evaluated the hematology responses of common South American toad Rhinella arenarum inhabiting natural and artificial environments associated with a fluorite mine from central Argentina. We analyzed three sampling stations associated with the fluorite mine: (I) Los Cerros Negros stream (CN), which runs on granitic rock with a high fluorite content; (II) Los Vallecitos stream (LV), which runs on metamorphic rock with low fluorite content; and (III) artificial decantation ponds (DP) containing sediments produced by fluorite flotation process. We calculated frequencies of micronuclei, erythrocyte nuclear abnormalities, mitosis, and immature erythrocytes. In addition, we performed a differential leukocyte count and determined neutrophils/lymphocyte ratio as a stress response estimator. We found high micronucleus (MN) and erythrocyte nuclear abnormality (ENA) frequencies in DP and CN but low frequencies in LV. The neutrophil/lymphocyte ratio was different among sites, with a significant increase in individuals from DP. Values registered in DP could be caused by exposure to mixture of compounds registered in dams that hold wastewater, while high values registered in CN stream might be due to natural concentrations of fluoride. Our results suggest that blood is an effective and non-destructive sensitive indicator for monitoring genotoxic agents in freshwater ecosystems.
Asunto(s)
Bufo arenarum/metabolismo , Daño del ADN , Fluoruros/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Argentina , Femenino , Masculino , Minería , Pruebas de MutagenicidadRESUMEN
Chemical defenses in amphibians are a common antipredatory and antimicrobial strategy related to the presence of dermal glands that synthesize and store toxic or unpalatable substances. Glands are either distributed throughout the skin or aggregated in multiglandular structures, being the parotoids the most ubiquitous macrogland in toads of Bufonidae. Even though dermal glands begin to develop during late-larval stages, many species, including Rhinella arenarum, have immature glands by the end of metamorphosis, and their post-metamorphic growth is unknown. Herein, we compared the post-metamorphic development of parotoids and dorsal glands by histological and allometric studies in a size series of R. arenarum. Histological and histochemical studies to detect proteins, acidic glycoconjugates, and catecholamines, showed that both, parotoids and dorsal glands, acquire characteristics of adults in individuals larger than 50 mm; that is, a moment in which the cryptic coloration disappears. Parotoid height increased allometrically as a function of body size, whereas the size of small dorsal glands decreased with body size. The number of glands in the dorsum was not linearly related to body size, appearing to be an individual characteristic. Only adult specimens had intraepithelial granular glands in the duct of the largest glands of the parotoids. Since toxic secretions accumulate in the central glands of parotoids, allometric growth of parotoids may translate into greater protection from predators in the largest animals. Conversely, large glands in the dorsum, which produce a proteinaceous secretion of unknown function, grow isometrically to body size. Some characteristics, like intraepithelial glands in the ducts and basophilic glands in the dorsum, are limited to adults.
Asunto(s)
Bufonidae/embriología , Metamorfosis Biológica , Piel/anatomía & histología , Animales , LarvaRESUMEN
In this work we showed the relationship between seasonal periods and the response of R. arenarum follicles and oocytes to different steroids. Using in vitro germinal vesicle breakdown (GVBD) assays, we demonstrated that P4 is the main steroid capable of inducing maturation in R. arenarum oocytes and follicles. In the second part of this work we showed that androgens can activate pre-maturation promoting factors (pre-MPFs) such as P4, by cytoplasm microinjection experiments. The results indicated that the steroids assayed induced oocyte and follicle maturation in a dose- and time-dependent manner. In oocytes, P4 was the most efficient steroid as a maturation inducer (EC50 of the reproductive period, 6 nM, EC50 of the non-reproductive period â 30 nM). Androgens (DHEA, dehydroepiandrosterone; T, testosterone; and AD, androstenedione) were less efficient maturation inducers than P4 (EC50 reproductive period â 50, 120 and 600 nM respectively). Similar results were obtained with intact follicles in both seasonal periods. Although the response of follicles to the different androgens was variable, in no case was it above the above the response induced by P4. Independently of the season, oocytes and follicles incubated in P4, P5 and T underwent GVBD after 6-10 h while oocytes and follicles incubated in DHEA and AD matured more slowly. Furthermore, we demonstrated that microinjection of mature cytoplasm from androgen-treated oocytes is sufficient to promote GVBD in immature recipient oocytes (DHEA, 57 ± 12%; AD, 60 ± 8%; T, 56 ± 13%). Thus, androgens such as DHEA, T and AD are as competent as P4 to activate pre-MPF.
Asunto(s)
Hormonas Esteroides Gonadales/farmacología , Factor Promotor de Maduración/metabolismo , Meiosis/efectos de los fármacos , Oocitos/efectos de los fármacos , Precursores de Proteínas/metabolismo , Andrógenos/administración & dosificación , Andrógenos/farmacología , Animales , Bufo arenarum , Células Cultivadas , Citoplasma/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Activación Enzimática/efectos de los fármacos , Femenino , Hormonas Esteroides Gonadales/administración & dosificación , Técnicas de Maduración In Vitro de los Oocitos/métodos , Microinyecciones , Oocitos/citología , Oocitos/fisiología , Oogénesis/efectos de los fármacos , Folículo Ovárico/citología , Folículo Ovárico/efectos de los fármacos , Folículo Ovárico/fisiología , Progesterona/administración & dosificación , Progesterona/farmacología , Estaciones del Año , Testosterona/administración & dosificación , Testosterona/farmacología , Factores de TiempoRESUMEN
El uso de biomarcadores hematológicos es importante para poder evaluar riesgos ambientales y la exposición a sustancias químicas potencialmente tóxicas y así poder desarrollar medidas que sirvan como señales de alarma temprana en ambientes contaminados. El objetivo de este trabajo fue determinar biomarcadores hematológicos en el sapo común Bufo (Rhinella) arenarum que proporcionen información para el diagnóstico de la salud de distintos ecosistemas de la provincia de Córdoba. Un total de 93 individuos adultos de Bufo (Rhinella) arenarum fueron capturados en cuatro sitios de la provincia de Córdoba y distintas variables ambientales del agua fueron medidas en cada sitio. Las muestras de sangre se obtuvieron mediante la punción de la vena angularis. Luego fueron teñidas con la tinción diferencial May Grünwald-Giemsa y fueron observadas mediante microscopio Zeiss Primo Star iLED para realizar el conteo de glóbulos blancos. Las variables ambientales del agua mostraron diferencias estadísticamente significativas entre las poblaciones, se registraron valores menores en “Alpa Corral”, mientras que “Villa Dálcar” presentó los mayores valores para dichas variables. No se encontraron diferencias estadísticamente significativas entre localidades en el recuento de glóbulos blancos (cada 1000 eritrocitos); sin embargo, en “Villa Dálcar” se registraron los ejemplares con mayor cantidad de leucocitos en el conteo de glóbulos blancos (425,48 ± 481,34). Mientras que para la fórmula leucocitaria, los linfocitos fueron las células más abundantes para los ejemplares de todos los sitios; encontrándose diferencias estadísticamente significativas entre cada localidad y “Alpa Corral”. Los ejemplares de “Villa Dálcar” presentaron diferencias estadísticamente significativas en relación a los monocitos y basófilos, registrándose altos valores para ambas células en los ejemplares de este sitio; mientras que en los ejemplares de “Cultivo” las diferencias se encontraron en eosinófilos y la relación neutrófilos/linfocitos. Estos resultados revelaron que de las cuatro localidades analizadas, “Villa Dálcar” representa la más afectada por las actividades antrópicas. Estas variaciones registradas en los parámetros hematológicos podrían considerarse evidencia de la posible presencia de agentes contaminantes en el lago “Villa Dálcar”.
Hematologic biomarkers are important to assess the environmental and health risks of exposure to potentially toxic chemicals, and for developing measures that serve as early warning signals in polluted areas. The aim of this study was to determine hematologic biomarkers of common toad Bufo (Rhinella) arenarum that provide information for the diagnosis of the health of ecosystems of Córdoba province. A total of 93 adult individuals of Bufo (Rhinella) arenarum were collected from four sites of Córdoba Province and hydric environmental variables were measured on each site. Blood samples were obtained by angularis vein puncture, smears of fresh blood were stained with May Grünwald-Giemsa and observed by using a microscope Carl Zeiss Primo Star (Pack 5), for white blood cell count. Water environmental variables showed statistically significant differences among localities, with the lowest values in “Alpa Corral” and highest values in “Villa Dálcar”. There were no statistically significant differences among individuals of different sites for white blood cells count. However, individuals from "Villa Dálcar" showed the highest number of white cells (425.48 ± 481.34). In the leukocyte formula, lymphocytes were most abundant white blood cells in individuals from all study sites. The blood parameters of toads from all sites showed statistically significant differences with individuals from “Alpa Corral”. "Villa Dálcar" Individuals exhibited significant differences in relation to monocytes and basophils with the highest values for both cell types. “Cultivo” locality showed significant differences for eosinophils and for the relationship neutrophils/ lymphocytes. These results revealed that “Villa Dálcar” represent the site most affected by human activities. In particular, changes recorded in hematological parameters could be giving evidence of the possible presence of contaminants in Lake “Villa Dálcar”.
Asunto(s)
Animales , Bufo arenarum/sangre , Recuento de Leucocitos/métodos , Argentina , Biomarcadores/sangre , Monitoreo del Ambiente/métodosRESUMEN
El uso de biomarcadores hematológicos es importante para poder evaluar riesgos ambientales y la exposición a sustancias químicas potencialmente tóxicas y así poder desarrollar medidas que sirvan como señales de alarma temprana en ambientes contaminados. El objetivo de este trabajo fue determinar biomarcadores hematológicos en el sapo común Bufo (Rhinella) arenarum que proporcionen información para el diagnóstico de la salud de distintos ecosistemas de la provincia de Córdoba. Un total de 93 individuos adultos de Bufo (Rhinella) arenarum fueron capturados en cuatro sitios de la provincia de Córdoba y distintas variables ambientales del agua fueron medidas en cada sitio. Las muestras de sangre se obtuvieron mediante la punción de la vena angularis. Luego fueron teñidas con la tinción diferencial May Gr³nwald-Giemsa y fueron observadas mediante microscopio Zeiss Primo Star iLED para realizar el conteo de glóbulos blancos. Las variables ambientales del agua mostraron diferencias estadísticamente significativas entre las poblaciones, se registraron valores menores en “Alpa Corral”, mientras que “Villa Dálcar” presentó los mayores valores para dichas variables. No se encontraron diferencias estadísticamente significativas entre localidades en el recuento de glóbulos blancos (cada 1000 eritrocitos); sin embargo, en “Villa Dálcar” se registraron los ejemplares con mayor cantidad de leucocitos en el conteo de glóbulos blancos (425,48 ± 481,34). Mientras que para la fórmula leucocitaria, los linfocitos fueron las células más abundantes para los ejemplares de todos los sitios; encontrándose diferencias estadísticamente significativas entre cada localidad y “Alpa Corral”. Los ejemplares de “Villa Dálcar” presentaron diferencias estadísticamente significativas en relación a los monocitos y basófilos, registrándose altos valores para ambas células en los ejemplares de este sitio; mientras que en los ejemplares de “Cultivo” las diferencias se encontraron en eosinófilos y la relación neutrófilos/linfocitos. Estos resultados revelaron que de las cuatro localidades analizadas, “Villa Dálcar” representa la más afectada por las actividades antrópicas. Estas variaciones registradas en los parámetros hematológicos podrían considerarse evidencia de la posible presencia de agentes contaminantes en el lago “Villa Dálcar”.(AU)
Hematologic biomarkers are important to assess the environmental and health risks of exposure to potentially toxic chemicals, and for developing measures that serve as early warning signals in polluted areas. The aim of this study was to determine hematologic biomarkers of common toad Bufo (Rhinella) arenarum that provide information for the diagnosis of the health of ecosystems of Córdoba province. A total of 93 adult individuals of Bufo (Rhinella) arenarum were collected from four sites of Córdoba Province and hydric environmental variables were measured on each site. Blood samples were obtained by angularis vein puncture, smears of fresh blood were stained with May Gr³nwald-Giemsa and observed by using a microscope Carl Zeiss Primo Star (Pack 5), for white blood cell count. Water environmental variables showed statistically significant differences among localities, with the lowest values in “Alpa Corral” and highest values in “Villa Dálcar”. There were no statistically significant differences among individuals of different sites for white blood cells count. However, individuals from "Villa Dálcar" showed the highest number of white cells (425.48 ± 481.34). In the leukocyte formula, lymphocytes were most abundant white blood cells in individuals from all study sites. The blood parameters of toads from all sites showed statistically significant differences with individuals from “Alpa Corral”. "Villa Dálcar" Individuals exhibited significant differences in relation to monocytes and basophils with the highest values for both cell types. “Cultivo” locality showed significant differences for eosinophils and for the relationship neutrophils/ lymphocytes. These results revealed that “Villa Dálcar” represent the site most affected by human activities. In particular, changes recorded in hematological parameters could be giving evidence of the possible presence of contaminants in Lake “Villa Dálcar”.(AU)
RESUMEN
Mature oocytes are arrested in metaphase II due to the presence of high levels of active maturation promoting factor (MPF). After fertilization, active MPF levels decline abruptly, enabling oocytes to complete meiosis II. One of the first and universal events of oocyte activation is an increase in cytosolic Ca2+ that would be responsible for MPF inactivation. Mature oocytes can also be activated by parthenogenetic activation. The aims of this work are to test the ability of dehydroleucodine (DhL) and its hydrogenated derivative 11,13-dihydro-dehydroleucodine (2H-DhL) to induce chemical activation in amphibian oocytes and to study the participation of calcium in the process. Results indicated that DhL and 2H-DhL induced oocyte activation in a dose-dependent manner. After 90 min of treatment, DhL 36 µM was able to induce 95% activation, while 2H-DhL 36 µM was less active, with only 40% activation. Our results suggest that DhL induced the inhibition of MPF activity, probably by an increase in intracellular Ca2+ concentration. Extracellular Ca2+ would not be significant, although Ca2+ release from intracellular stores is critical. In this sense, IP3Rs and RyRs were involved in the Ca2+ transient induced by lactones. In this species, RyRs appears to be the largest contributor to Ca2+ release in DhL-induced activation. Although more studies are needed on the mechanism of action through which these lactones induce oocyte activation in Rhinella arenarum, the results of this research provide interesting perspectives for the use of these lactones as chemical activators in in vitro fertilization and cloning.
Asunto(s)
Bufo arenarum , Lactonas/farmacología , Oocitos/efectos de los fármacos , Oocitos/fisiología , Sesquiterpenos/farmacología , Animales , Calcio/metabolismo , Células Cultivadas , Relación Dosis-Respuesta a Droga , Ácido Egtácico/análogos & derivados , Ácido Egtácico/farmacología , Femenino , Técnicas de Maduración In Vitro de los Oocitos , Receptores de Inositol 1,4,5-Trifosfato/metabolismo , Masculino , Factor Promotor de Maduración/antagonistas & inhibidores , Factor Promotor de Maduración/metabolismo , Canal Liberador de Calcio Receptor de Rianodina/metabolismoRESUMEN
There are no studies that document the production of prostaglandins (PGs) or their role in Rhinella arenarum oocyte maturation. In this study, we analysed the effect of arachidonic acid (AA) and prostaglandins (PGs) on maturation, activation and pronuclear formation in R. arenarum oocytes. Our results demonstrated that AA was capable of inducing maturation in time-dependent and dose-dependent manner. Arachidonic acid-induced maturation was inhibited by indomethacin. PGs from AA hydrolysis, such as prostaglandin F2α (PGF2α) and, to a lesser extent, PGE2, induced meiosis resumption. Oocyte maturation in response to PGF2α was similar to that produced by progesterone (P4). Oocyte response to PGE1 was scarce. Rhinella arenarum oocyte PGF2α-induced maturation showed seasonal variation. From February to June, oocytes presented low sensitivity to PGF2α. In following periods, this response increased until a maximum was reached during October to January, a close temporal correlation with oocyte response to P4 being observed. The effect of PGF2α on maturation was verified by analysing the capacity of oocytes to activate and form pronuclei after being injected with homologous sperm. The cytological analysis of activated oocytes demonstrated the absence of cortical granules in oocytes, suggesting that PGF2α induces germinal vesicle breakdown (GVBD) and meiosis resumption up to metaphase II. In turn, oocytes matured by the action of PGF2α were able to form pronuclei after fertilization in a similar way to oocyte maturated by P4. In microinjection of mature cytoplasm experiments, the transformation of pre-maturation promoting factor (pre-MPF) to MPF was observed when oocytes were treated with PGF2α. In summary, our results illustrated the participation of the AA cascade and its metabolites in maturation, activation and pronuclei formation in R. arenarum.
Asunto(s)
Ácido Araquidónico/metabolismo , Bufo arenarum , Oocitos/fisiología , Animales , Ácido Araquidónico/farmacología , Núcleo Celular/efectos de los fármacos , Núcleo Celular/metabolismo , Dinoprost/farmacología , Femenino , Técnicas de Maduración In Vitro de los Oocitos , Indometacina/farmacología , Masculino , Microinyecciones , Oocitos/citología , Oocitos/efectos de los fármacos , Oocitos/metabolismo , Folículo Ovárico/efectos de los fármacos , Progesterona/farmacología , Estaciones del AñoRESUMEN
The advancing agricultural frontier has led to an important loss of natural habitats, with significant consequences for biodiversity. The demography for two species of anurans, Physalaemus biligonigerus and Rhinella arenarum, both associated with agricultural systems in the central region of the Córdoba Province, were analyzed and compared in this study. Four sites were sampled: three agroecosystems with different alteration degrees (C1, C2 and SM1) and a fourth site not cultivated (SM2). The sampling was conducted during two reproductive periods, from September 2008 to April 2009 and September 2009 to April 2010. Individuals were captured using live pitfall traps for the metamorphic, juveniles and adults; and visual encounter survey, for the capture of eggs and larvae. With the abundance data, the survival for each age class was estimated using the KNM method (Kiritani Nakasuki Manly). With survival rates and fertility population, Leslie matrices were elaborated to obtain a quantitative projection of the population size. Altered environments showed lower eggs and larvae survival. Population pro-jections were favorable in the site SM2 and were less favorable and a tendency to extinction, in sites dominated by crops. This study showed that the agroecosystems of this region are possibly inhospitable environments for reproduction and survival of the species studied. The aquatic stages in the life cycle of both species would be the more affected, since water bodies deterioration is present or may occur in those areas. We can recognize species-specific effects of agricultural ecosystems; P. biligonigerus was the most affected species, possibly because of their life histories and habitat requirements. We suggested that environmental degradation caused by the cropland in the central region of Argentina would impact on the demographics of the anuran populations in the area.
El crecimiento de la agricultura produce pérdida del hábitat natural, con consecuencias para la biodiversidad de los anfibios. Se analizó la demografía poblacional de dos especies de anfibios en agroecosistemas de la provincia de Córdoba, Rhinella arenarum y Physalaemus biligonigerus. Los muestreos se realizaron en tres agroecosistemas y en un cuarto sitio, no afectado por cultivos. Los individuos se capturaron utilizando trampas de caída viva y relevamientos visuales. Con los datos de abundancia se estimó la supervivencia para cada clase de edad y con las tasas de supervivencia y fertilidad poblacional, se construyeron matrices de Leslie para obtener una proyección cuantitativa del tamaño poblacional. Las proyecciones poblacionales fueron favorables para el sitio SM2 y desfavorables para los sitios cultivados. Los agroecosistemas son ambientes posiblemente inhóspitos para la reproducción y supervivencia de las especies estudiadas. Particularmente se ven afectados aquellos estadios acuáticos del ciclo de vida de estas especies, debido al deterioro de los cuerpos de agua en estas áreas. Se reconocieron efectos especie-específicos de los ecosistemas agrícolas, ya que P. biligonigerus resultó la especie más afectada. Se sugiere un deterioro ambiental producido por cultivos extensivos de soja, lo que impactaría la demografía de las poblaciones de anuros.
Asunto(s)
Animales , Anuros/clasificación , Ecosistema , Agricultura , Argentina , Anuros/fisiología , BiodiversidadRESUMEN
Trophic ecology in tadpoles of Rhinella arenarum (Anura: Bufonidae) in agroecosystems and their possible implications for conservation. The progress of the agriculture border has led an important loss of natural habitats, with significant consequences for biodiversity. In this sense, the studies in anuran amphibian tadpoles inhabiting these environments are relevant, because the larval stage is a phase of population regulation. The aim of this study was to analyze the body condition and diet in Rhinella arenarum, tadpoles, an anuran species widely distributed in South America and that inhabit agroecosystems. Three sites were sampled, two agroecosystems with different alteration degrees (C1 and C2) and an uncultured (SM) third place. The captured tadpoles were anesthetized, fixed and preserved in formaldehyde (10%). Subsequently, body measurements were made and the complete intestine was removed and analyzed for food items under a binocular microscope. The diet in R. arenarum tadpoles has a dominance of algae Bacillariophyceae, followed by Cyanophyceae. In particular, the class Bacillariophyceae, due to the presence of the genus Navicula, Nitzschia, Gomphonema and Hantzschia, was important in the diet of the anurans in those agroecosystems. Class Cyanophyceae, mainly represented by genus Oscillatoria and Euglenophyceae represented by Euglena and Strombomonas, were predominant in the diet of the anurans in SM. Some differences in the total items consumed by tadpole were observed between the studied sites. Tadpoles that inhabit the modified sites (C1 and C2) recorded a significantly smaller amount of food. Moreover, the tadpoles that inhabit these sites showed a lower body condition. The presence of certain algae associated with eutrophic environments, could indicate some pollution in agroecosystems (C1 and C2). Food resources would be lesser in places with strong agricultural activity, possibly with a greater degree of eutrophication. A smaller food amount could have consequences at population level for the short and long time terms, because of its impact on individual growth. Larval diet is suggested as a potential bioindicator of environmental health for these areas. Rev. Biol. Trop. 60 (2): 771-779. Epub 2012 June 01.
El crecimiento de la agricultura produce perdida del habitat natural, con consecuencias para la biodiversidad de los anfibios. Se analizo la dieta y condición corporal de larvas de anuros de Rhinella arenarum que habitan agroecosistemas. Los muestreos fueron realizados en dos agroecosistemas y en un tercer sitio, no afectado por cultivos. Las larvas capturadas fueron anestesiadas, fijadas y preservadas en formaldehido, se realizaron medidas corporales y se analizo la dieta de las larvas. Se registro diversidad en la oferta alimenticia proporcionada por los distintos ambientes. La dieta tuvo una predominancia de algas Bacillarophyceae, seguidas por Cyanophyceae. Particularmente, los géneros Navicula, Nitzschia, Hantzschia y Gomphonema (clase Bacillarophyceae), fueron importantes en los agroecosistemas. Los géneros Osillatoria, Euglena y Strombomonas (clases Cyanophyceae y Euglenophyceae), predominaron en la dieta de las larvas de anuros en el sitio menos alterado. Las larvas de los sitios más alterados consumen menor cantidad de alimento y registran una menor condición corporal. La presencia de determinadas algas, indicarían un mayor grado de contaminación en los agroecosistemas. La eutrofización de lagunas podría alterar la disponibilidad de alimento para larvas de anuros que podría tener consecuencias poblacionales negativas. Se sugiere el análisis de dietas larvarias como un potencial bioindicador de salubridad ambiental.
Asunto(s)
Animales , Bufo arenarum/crecimiento & desarrollo , Ecosistema , Agricultura , Argentina , Bufo arenarum/fisiología , Monitoreo del Ambiente , Conducta Alimentaria/fisiología , Larva/crecimiento & desarrollo , Larva/fisiologíaRESUMEN
The regulation of body temperature in ectotherms has a major impact in their physiological and behavioral processes. Observing changes in thermal parameters related with reproduction allows us to better understand how Rhinella arenarum optimizes a thermal resource. The aim of this study was to compare the thermal parameters of this species between breeding and non-breeding periods. In the field, we recorded the body temperature from captured animals, the air temperature, and the temperature of the substrate. In the laboratory, we measured the temperature R. arenarum selected on a thermal gradient and the critical extreme temperatures. The results of our study show variations in thermal parameters between the two situations studied. This species makes efficient use of thermal resources during the breeding period by basking to significantly increase body temperature. Because calling is energetically costly for males, this behavior results in increased efficiency to callers during the breeding period. Rev. Biol. Trop. 59 (1): 347-353. Epub 2011 March 01.
La regulación de la temperatura en ectotérmos tiene gran importancia en los procesos fisiológicos y comportamentales. Los cambios en los parámetros térmicos relacionados con la reproducción nos permiten entender de qué manera Rhinella arenarum optimiza el recurso térmico. El objetivo del presente trabajo fue comparar los parámetros térmicos de la especie entre el periodo reproductivo y no reproductivo. En el campo se registraron la temperatura corporal de los animales capturados, la temperatura del aire y del sustrato. Además, en laboratorio se registro la temperatura selecta en un gradiente térmico. Como así también las temperaturas criticas máxima y mínima. Los resultados de nuestro estudio muestran variaciones de los parámetros térmicos entre ambas situaciones estudiadas. Aparentemente esta especie hace un uso eficiente del recurso térmico durante el periodo reproductivo ya que el basking le permite aumentar considerablemente la temperatura corporal, probablemente este comportamiento esté relacionado con el aumento de la eficacia para emitir el canto durante el periodo de reproducción ya que el mismo es energéticamente costoso para los machos.
Asunto(s)
Animales , Masculino , Regulación de la Temperatura Corporal/fisiología , Bufo arenarum/fisiología , Reproducción/fisiologíaRESUMEN
The water balance and the upper limit of osmotic tolerance of premetamorphic Rhinella arenarum larvae (Gosner's stage 26) was evaluated after semistatic incubation in electrolyte (NaCl) and non-electrolyte (mannitol) media following a protocol of progressively increased osmotic pressure. Wet and dry weights were measured to calculate the water content as a derived variable indicative of the hydric balance. Statistical analysis was performed using univariate and integrated multivariate analysis. Tadpoles survived in electrolyte and non-electrolyte solutions up to 200 mOsm. The discriminant function was the best tool to describe the responses of the animals to external environmental stress under experimental conditions. The results were compared with those obtained in previous studies using a protocol of acute exposure to the same media used in this study. It was concluded that a) multivariate analysis is an appropriate approach to describe the responses of tadpoles to changes in the environmental physicochemical parameters, and b) progressive and acute acclimation to the experimental solutions induced similar responses.
Avaliou-se o balanço hídrico e o limite superior de tolerância osmótica em larvas pré-metamórficas do Rhinella arenarum (etapa 26 de Gosner) sob condições de incubação semiestáticas, num meio eletrolítico (NaCl) e não eletrolítico (manitol), seguindo um protocolo de aumento progressivo da pressão osmótica do meio. A quantificação das respostas se efetuou por meio da medição dos valores de peso úmido e seco e do cálculo, a partir destes, do conteúdo de água, como variável derivada indicativa do equilíbrio hídrico. A análise estatística foi realizada usando análise univariada e multivariada. As larvas conseguiram sobreviver em soluções eletrolíticas e não eletrolíticas até 200 mOsm. A função discriminante foi a melhor ferramenta para descrever as respostas dos animais ao estresse osmótico ambiental. Os resultados foram comparados com os obtidos em estudos anteriores, usando um protocolo de exposição aguda aos mesmos meios de incubação usados neste estudo. Concluiu-se: a) a análise multivariada é a aproximação adequada para descrever as respostas das larvas às mudanças nos parâmetros físico-químicos do seu meio; e b) tanto a aclimatação progressiva, como as exposições agudas às soluções experimentais induziram as respostas semelhantes.