Pesticides with chlorpyrifos and endosulfan as active element are used for pest control on agricultural lands and are high-risk inputs in aquatic systems. The acute toxicity of these insecticides in the freshwater prawn Palaemonetes argentinus was evaluated. The results were used to determine the lowest observed-effect and no observed-effect concentrations. Individual growth of prawns in relation to chlorpyrifos and endosulfan exposure was analyzed. LC(50) values to chlorpyrifos and endosulfan exposure were 2.98 microg L(-1) and 14.10 at 24 hours and 0.49 microg L(-1) and 6.28 microg L(-1) at 96 hours of exposure, respectively. The size increment of prawns was the same in all treatments; cephalothorax length increased linearly per molt. The intermolt period was influenced by the toxic effect of pesticides during rearing time, and this decreased with the molt cycles compared with the normal growth pattern. The results suggest that juveniles of P. argentinus are sensitive to chlorpyrifos and endosulfan pollution.

No abstract

No abstract

No abstract

ABSTRACT. During the two-month rearing period, the effect of four water temperatures (15°C, 20°C, 25°C and 30°C) on survival rate, number of molts, and growth rate (molt increment and intermolt period) of juvenile Macrobrachium borellii Nobili, 1896 and Palaemonetes argentinus Nobili, 1901 prawns was evaluated in laboratory conditions. The two species showed some similarities in their both survival and growth pattern at different temperatures. The survival rate was highest at 20°C and 25°C, decreasing at the lowest temperature. The number of molts increased at higher temperatures, ranging the intermolt period from 22.2 days to 9.9 days, for M. borellii, and from 20.8 to 9.5 days for P. argentinus, corresponding those values to 15°C and 30°C, respectively. No difference between species was noted in the intermolt period. The size increment by molting increased significantly from 15°C to 25°C, whereas a reduction in the growth of prawns was observed at 30°C. Significant differences among temperatures were found in the slope of regressions between the size increment by molting and the cephalothorax length. M. borellii showed a significantly higher tolerance to elevated temperature and a faster growth (about twice at 25°C) than P. argentinus. These differences could provide M. borellii a competitive advantage for a better adaptation to the dynamic of freshwater environment, especially in areas with anthropogenic impact. KEYWORDS.Decapods, molt increment, intermolt period, temperature. RESUMEN. Efecto de la temperatura sobre la supervivencia y el crecimiento de los camarones dulciacuícolas Macrobrachium borellii y Palaemonetes argentinus (Crustacea, Palaemonidae). Durante un período de crianza de dos meses, se evaluó en condiciones de laboratorio el efecto de cuatro temperaturas (15°C, 20°C, 25°C y 30°C) sobre la supervivencia, número de mudas y crecimiento (incremento en muda y período de intermuda) de camarones juveniles de Macrobrachium borellii Nobili, 1896 y Palaemonetes argentinus Nobili, 1901. Ambas especies mostraron similitudes en la supervivencia y en el patrón de crecimiento, a las diferentes temperaturas. La supervivencia fue mayor a 20°C y 25°C, y disminuyendo a la menor temperatura. El número de mudas se incrementó con la temperatura, variando el período de intermuda entre 22,2 y 9,9 días en M. borellii y entre 20,8 a 9,5 días en P. argentinus, correspondiendo tales valores a 15°C y 30°C respectivamente. No se detectaron diferencias entre ambas especies en el período de intermuda. El incremento de tamaño por muda aumentó significativamente de 15°C a 25°C, reduciéndose en los camarones criados a 30°C. La pendiente de regresión entre el incremento de tamaño por muda y el largo del cefalotórax mostró variaciones significativas entre las temperaturas. El camarón M. borellii mostró una elevada tolerancia a la alta temperatura y un rápido crecimiento (casi el doble a 25°C) en comparación con P. argentinus. Estas diferencias podrían brindarle a M. borellii una ventaja competitiva para adaptarse a la dinámica de...

No abstract

No abstract

No abstract