No abstract

No abstract

The aim of this study was to evaluate the acute and chronic effects caused by exposure to the 2,4 dichlorophenoxyacetic acid (2,4-D)-based commercial herbicide Amina Zamba® on Physalaemus albonotatus tadpoles from Gosner stage 25. The lethal concentration (LC50) was determined after exposure to different concentrations of Amina Zamba® (350 to 2400 mg/L) at 96 h. Sublethal effects were evaluated after chronic exposure to four fractions of the LC50 96h obtained (12.5, 25, 50, and 75% of LC50 96h ) and a control. The biological responses analyzed included survival, growth and development, morphological abnormalities, and histological changes in the liver. The LC50 values of Amina Zamba® at 48, 72, and 96 h were 1040.2, 754.2, and 350 mg/L, respectively. The chronic exposure to the herbicide altered the survival of exposed tadpoles and caused several morphological abnormalities and liver histological alterations, mainly at the highest concentra-tions tested. Oral disc malformations and intestinal abnormalities were the most frequent abnormalities in all treated tadpoles. Histological alterations observed in the liver structure included hepatocyte vacuolization, enlargement of sinusoids, dilation of blood vessels, and a s i g n i f i c a n t i n c r e a s e i n t h e n u m b e r o f melanomacrophages in tadpoles exposed to 25, 50, and 75% LC50 96h with respect to control (P < 0.05). Furthermore, the treated tadpoles showed an accelerated development rate, reaching Gosner stages 38 and 42 before controls. These results demonstrate that the chronic exposure to this commercial formulation affects the survival, accelerates metamorphosis, and induces morphological abnormalities and liver damage in P. albonotatus tadpoles.

ABSTRACT. Reproductive aspects of Dendropsophus sanborni (Anura, Hylidae) in northeastern Argentina. The aim of this investigation was to characterize reproductive aspects of Dendropsophus sanborni (Schmidt, 1944) (Anura, Hylidae) in the northwest of Corrientes province, in northeastern Argentina. The reproductive cycles of males and females, the existence of sexual dimorphism and the male's vocalization period were analyzed. Samplings were made from September 2011 to August 2012. Dendropsophus sanborni showed a prolonged reproductive pattern because reproductive activity was observed during most part of the year. Calling males were recorded all months except in July. The spermatogenic cycle can be characterized as potentially continuous. In males, snout-vent length was significantly correlated with mean testicular volume. The species showed sexual dimorphism in body mass, with females larger than males. Post-ovulatory females were found from March to June and most females had oocytes at different stages of maturity, with abundant post-vitellogenic oocytes from August to December. KEYWORDS.Reproduction, vocalizations, gonads. RESUMEN. Aspectos reproductivos deDendropsophus sanborni (Anura, Hylidae) en el nordeste de la Argentina. El objetivo del presente estudio fue caracterizar aspectos reproductivos de Dendropsophus sanborni (Schmidt, 1944) (Anura, Hylidae) en la región noroeste de la provincia de Corrientes, al Nordeste de Argentina. Para esto, se analizó el ciclo gonadal de machos y hembras, la existencia de dimorfismo sexual y el periodo de vocalización de los machos. Los muestreos se efectuaron desde Septiembre de 2011 hasta Agosto de 2012. Dendropsophus sanborni exhibe un patrón reproductivo prolongado, dado que la actividad reproductiva ocurre durante gran parte del año. Se registraron machos en actividad de vocalización durante todos los meses excepto en julio. El ciclo espermatogénico puede ser caracterizado como potencialmente continuo. En los machos hubo correlación significativa entre la longitud hocico-cloaca y el volumen testicular medio. La especie presentó dimorfismo sexual en relación a la masa corporal, siendo las hembras mayores que los machos. Se encontraron hembras post-ovulatorias desde Marzo a Junio y una mayor proporción de hembras con ovocitos en diferentes estados de maduración, con abundantes ovocitos post-vitelogénicos, en los meses de Agosto a Diciembre.

No abstract

Se cuantificaron y compararon los melanomacrófagos (MM) y la actividad de la enzima Glutatión S−Transferasa (GST) en hígados de ejemplares adultos de Leptodactylus  chaquensis (Anura, Leptodactylidae) colectados en un cultivo de arroz (CA) (siete días posteriores a la aplicación de clorpirifos, CPF) y en un sitio de referencia (SR) en el departamento San Javier, provincia de Santa Fe (Argentina). El análisis histológico reveló una mayor cantidad (p = 0.028) y área ocupada por MM (p = 0.017) y se registró una inhibición en la actividad de la GST (p = 0.030) en individuos del CA respecto a los del SR. Los efectos descriptos evidencian el riesgo ecotoxicológico para los anuros en los cultivos de arroz con aplicaciones de CPF.

Tadpoles detect chemical signals released from predators and conspecifics, and those present in the environment, and adjust their behavioral responses. This study evaluated the swimming activity of Rhinella dorbignyi (Duméril and Bibron, 1941) tadpoles exposed to chemical signals, including cues from a predator fish Synbranchus marmoratus Bloch, 1975 and an injured conspecific; sublethal concentration of insecticide cypermethrin; and their combination. Swimming behavior (total distance moved, average speed, global activity, number of contacts between tadpoles) was evaluated in an individual (1) and groups of different size (3, 5, 7 and 10 tadpoles) using a video-tracking software tool. Predator exposure modified behavioral parameters, reducing encounters with predators and, therefore, mortality. Total distance moved and average speed increased in trials involving 1 tadpole and 3 interacting tadpoles exposed to injured conspecifics, whereas global activity increased in all group sizes, showing that gregarious tadpoles may be affected by alarm cues and their behavior may be disrupted. The insecticide treatments (alone and combined) increased parameters in all group sizes, causing hyperactivity due to its neurotoxic effect. The different responses observed after exposure to alarm cues and environmental signals in the different group sizes modified the normal behavior and the ecological dynamics of gregarious tadpoles.

No abstract