The adverse effects of the phenylpyrazole, fipronil, on juvenile white shrimp Litopenaeus setiferus.

Chemical pesticides are commonly used world-wide, and they can flow into estuaries and affect non-targeted organisms. We evaluated the effects of six concentrations of the phenylpyrazole, fipronil (0.0, 0.005, 0.01, 0.1, 1.0, and 3.0 µg/L), which are environmentally relevant, on white shrimp Litopenaeus setiferus (initially averaging 0.80 ± 0.08 g/shrimp). Compared with the control, survivorship of shrimp over 45 days declined significantly at the higher concentration treatments. Growth was affected at all concentrations, and the percent weight gain decreased significantly. Inter-molt intervals were longer in all treatments. Changes in swimming and feeding behavior of shrimp were observed under all treatments, and change in body color was observed at higher concentration treatments. Lipid content in shrimp decreased significantly while ash content increased with fipronil concentration. Fipronil adversely affected white shrimp under the concentrations observed in the environment and monitoring of fipronil use is needed in coastal areas.

Effects of insecticides, fipronil and imidacloprid, on the growth, survival, and behavior of brown shrimp Farfantepenaeus aztecus.

Increased use of pesticide is causing detrimental effects on non-target species worldwide. In this study, we examined the lethal and sub-lethal effects of fipronil and imidacloprid, two commonly used insecticides, on juvenile brown shrimp (Farfantepenaeus aztecus), one of the most commercially and ecologically important species in the United States. The effects of six concentrations of fipronil (0.0, 0.005, 0.01, 0.1, 1.0, and 3.0 µg/L) and six concentrations of imidacloprid (0.0, 0.5, 1.0, 15.0, 34.5, 320.0 µg/L) were tested in a laboratory. We examined five different endpoints: growth, moulting interval, survivorship, behavioral change, and body color change. Growth of shrimp was reduced significantly under higher concentrations of both insecticides. Under fipronil exposure, shrimp in control showed the shortest inter-moult interval (7.57 ± 2.17 day) compared with other treatments; similarly, in the imidacloprid experiment, moulting increased from 8.43 ± 2.52 day in control to 11.95 ± 4.9 day in 0.5 µg/L treatment. Higher concentrations of fipronil (1.0 and 3.0 µg/L) showed a 0.0% survival rate compared with 100% survival in the control and 0.005 µg/L treatment. Under imidacloprid, survivorship decreased from 100% in the control to 33.33% in the 320.0 µg/L treatment. The 96-h LC50 of fipronil was 0.12 µg/L, which makes brown shrimp one of the most sensitive invertebrates to the pesticide. Changes in behavior and body color were observed under both insecticides after different durations of exposures depending on concentrations. We conclude that, at the corresponding EPA benchmark concentrations, fipronil had more lethal effects than imidacloprid, and imidacloprid had more sub-lethal effects than fipronil. Both effects are of serious concern, and we suggest monitoring is necessary in estuaries.

Lethal and sub-lethal effects of the insecticide fipronil on juvenile brown shrimp Farfantepenaeus aztecus.

Chemical pesticides are widely used around the world, but at the same time, they may cause direct or indirect risks to many non-target organisms. Recent increased use of insecticides in coastal areas, for example to control invasive tawny crazy ants, raises concern that insecticides may affect ecologically and/or commercially important species found in estuaries. Here, we investigated the lethal and sub-lethal effects of fipronil on juvenile brown shrimp Farfantepenaeus aztecus over 29 days at five different nominal concentrations (0.1, 1.0, 3.0, 6.4, and 10.0 µg/L) in a laboratory experiment. Exposure to all of the fipronil treatments resulted in all individuals dying before the end of the experiment; whereas, no individual died in the control (0.0 µg/L). The 96-hour LC50 was determined to be 1.3 µg/L. Shrimp also experienced weight loss under all of the fipronil treatments. Inter-moult interval was increased from 12.2 ± 1.64 day in the control group to 15.5 ± 0.53 day in the 1.0 µg/L treatment. Lipid content of shrimp increased significantly in a concentration-dependent manner. Finally, behavioral and body color changes were also observed under the fipronil treatments. We conclude F. aztecus is very sensitive to fipronil and monitoring is needed in coastal areas.