Abstract
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.
Highlights
Chemical pesticides are commonly used for both agricultural and household purposes world- wide to control pests
Many recent studies have demonstrated the occurrence of fipronil and its degradation products, which have the same or greater toxic properties and are more stable than fipronil itself[21,25,26,27], in the aquatic environment at levels ranging between 0.001–10.004 μg/L, often exceeding the acute level (0.1 μg/L) of fipronil in the aquatic life benchmark of the U.S EPA22,28–31
Our results showed that survival of juvenile shrimp decreased significantly with fipronil concentration, from 0.1 μg/L to 10.0 μg/L (Kaplan-Meier survival curve analysis followed by the non-parametric Log-Rank test, P < 0.0001) as shown in Table 2 and Fig. 2
Summary
Chemical pesticides are commonly used for both agricultural and household purposes world- wide to control pests They are known to have negative side effects on non-target organisms, including terrestrial organisms such as birds[1,2,3] and insects[4,5,6] as well as aquatic organisms such as fish[7,8,9] and arthropods[10,11]. Fipronil is considered one of the most effective phenylpyrazole insecticides, which are used widely, and it is considered to affect arthropods selectively[19,20] It is used increasingly for the protection of crops such as rice, corn, cotton, potatoes, turnips, and rutabagas from herbivorous insects and for controlling ticks and fleas on animals[13,21,22]. The number of species studied is still limited, and most focused on lethal effects
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