Acute toxicity test of two pesticides diazinon and deltamethrin on spirlin ( Alburnoides bipunctatus ) larvae and fingerling

The present research was performed to determine and compare acute toxicity of diazinon and deltamethrin to spirlin larvae and fingerling. Diazinon and deltamethrin are common useful agricultural pesticides. LC50 of 24, 48, 72 and 96 h was attained by probit analysis software SPSS Version 16. Fish samples (21 fish in each test group) were exposed to different concentrations of diazinon and deltamethrin (diazinon: for fingerling between 1 to 20 ppm and larvae 0.25 to 2 ppm; deltamethrin: for fingerling between 0.01 to 0.2 ppm and larvae 0.0025 to 0.02 ppm) for 96 h and mortality were recorded. The LC50 96 h of diazinon for fingerlings and larvae were 7.88 and 0.69, respectively. The LC50 96 h of deltamethrin for fingerlings and larvae were 0.27 and 0.006 ppm, respectively. According to the results, larvae are more sensitive than fingerlings. In the present study, LC50 values indicated that deltamethrin is more toxic than diazinon to this species.


INTRODUCTION
Fresh water is a valuable resource and the increasing pollution of our rivers and lakes is a cause for alarm.During the last decades, significant amounts of pesticides belonging to the classes of organophosphates have been released into the environment.The use of diazinon and deltamethrin is common to control herbal pests in many agriculture fields that are located in the vicinity of fresh water resources.
Diazinon is an organophosphorus compound with an anticholinesterase mode of action (Tinoco-Ojanguren and Halperin, 1998).It is used extensively to control flies, lice, insect pests of ornamental plants and food crops, as well as nematodes and soil insects in lawns and croplands.Diazinon degrades rapidly in the environment, with halftime persistence usually less than 14 days.But under conditions of low temperature, low moisture, high alkalinity and lack of suitable microbial degraders, diazinon may remain biologically active in soils for 6 months or longer (Eisler, 1986).Because of its aquatic distribution, diazinon affects a wide range of non-target organisms, like invertebrates, mammals, birds and fishes, especially those inhabiting aquatic environment (Burkepile et al., 2000;Hamm and Hinton, 2000).
Alburnoides bipunctatus inhabit streams and rivers in foothills with well oxygenated, fast-flowing water.All age classes occur in open water of streams and small rivers (Kottelat and Freyhof, 2007).Found also in rivers with very calm waters, are feeds on insect larvae and dead insects as well as on crustaceans and diatoms (Vostradovsky, 1973).
A. bipunctatus was selected for the bioassay experiments, because it is widespread in most part of Europe and Asia and it can be found in Marine-Neritic, Marine-Oceanic, Brackish water and Freshwater.

MATERIALS AND METHODS
The purpose of this research was to determine the toxicity of diazinon and deltamethrin on A. bipunctatus larvae and fingerlings.Lethal experiments were conducted using 125 larvae and 125 fingerling for each of the tested pesticides.Physicochemical properties of water were as follows: 23±1°C temperature, 7 to 9/5 mg/L dissolved oxygen, pH 6.5 to 8 and 220 mg/L total hardness.During the experiment, water was not exchanged.Before the test, fish were fed twice daily with Biomar feed of 2% body weight.
Concentrations of diazinon were 1, 5, 10, and 20 for fingerlings and 0.25, 0.5, 1 and 2 mg/L for larvae.These concentrations for deltamethrin were 0.01, 0.05, 0.1 and 0.2 for fingerling and 0.0025, 0.005, 0.01 and 0.02 for each pesticide fingerlings and larvae were divided into five groups of 21 separately.So there were four group as follows: fingerlings by diazinon, larvae by diazinon, fingerling by deltamethrin and larvae by deltamethrin.In each group, there were 4 treatments and 1 control.Mortality rates were recorded at time 0, 24, 48, 72 and 96 h.
Experiments were performed according to the Organization for Economic Co-operation and Development (OECD) standard method (1998), to determine the LC50 96 h of spirlin larvae and fingerlings.Number of dead fish was recorded at time 24, 48, 72, and 96 h.Acute toxicity tests was carried out according to Hotos and Vlahos (2000).
The results of this study indicated that LC 50 96 h of diazinon is 7.88 ppm for fingerling and 0.69 ppm for larvae, thus maximum allowable concentration (MAC) value is equal to 0.788 and 0.069 ppm, respectively (Tables 3 and 4).As well as for deltamethrin, MAC value for fingerling and larvae is equal to 0.027 and 0.0006, respectively.
The results indicated that spirlin larvae are more sensitive than fingerlings, exposed to pesticides deltamethrin and diazinon.Moreover, deltamethrin is more toxic to A. bipunctatus than diazinon.

DISCUSSION
Today, diazinon is used extensively by commercial and home applicators in a variety of formulations to control flies, cockroaches, lice on sheep, insect pests of ornamental plants and food crops (especially corn, rice, onions, and sweet potatoes), forage crops such as alfalfa,and nematodes and soil insects in turf, lawns, and croplands (Anon, 1972;Meier et al., 1976;Allison and Hermanutz, 1977;Berg, 1984;Stone and Gradoni, 1985;Eisler, 1986).Organophosphate compounds are generally lipophilic and easily absorbs through the skin, gills and digestive system and pass through blood and brain barrier (Vale, 1998), because the inhibition of acetylcholinesterase activity in fish can cause changes in behavior, severe abnormalities in growth and nutrition, and survival rates of behavioral disorders in their breeding (Dutta and Arends, 2003).One of the pyrethroids has been found wide acceptability and is extremely used in agriculture and forestry, because of its high activity against a broad spectrum of insect pests (Villarini et al., 1998) such as deltamethrin.However, its effects on nervous, respiratory, and hematological systems in fishes have been reported (Pimpão et al., 2007;Ural and Sağlam, 2005).Therefore, to evaluate the effect of pesticides on aquatic organisms are important.
In this study, fingerlings and larvae were used, because toxins are very influential in the early stages of life, especially during the larval stage, as the effect of deltamethrin on the sensitive early life stages of zebrafish, Brachydanio rerio, were examined by Gӧrge and Nagel (1990).Deltamethrin can be highly toxic to fish.The development of larvae was influenced by deltamethrin.The United States Department of Agriculture (USDA) National Agricultural Pesticide Impact Assessment Program's document reports that deltamethrin has acute toxicity to fish in laboratory tests to be in the average range LC 50 value of 1 to 10 µg/L (Kӧprϋcϋ and Aydın, 2004).According to the results, LC 50 96 h of deltamethrin were 0.27 and 0.006 ppm for fingerling and larvae, respectively.
In this study, LC 50 96 h of diazinon was 7.88 and 0.69 ppm for fingerling and larvae, respectively.According to the same research, freshwater teleosts were comparatively resistant to diazinon, with all LC 50 96 h values greater than 90 µg/L.Sublethal effects were recorded at 0.3 to 3.2 µg/L diazinon and they include reduced emergence of stream insects (0.3 µg/L), reduced fecundity of a marine fish (0.47 µg/L), significant accumulations in freshwater teleosts (0.55 µg/L), potential mutagenicity in a freshwater fish (1.6 µg/L), and spinal deformities in teleosts (3.2 µg/L) (Eisler, 1986).In comparison with other results, A. bipunctatus is a semiresistant species against diazinon and it is highly toxic.A. bipunctatus and abnormal behaviors observed in fish exposed to acute toxicity, including severe restlessness, anxiety, loss of ability to orient in water, swimming in a semi-circle, and dark body, confirm referred symptoms in previous reports (Pazhand, 1999).
Studies that indicate low level of deltamethrin (0.005 µg/L) in the aquatic environment may have a significant effect on carp populations.Being a general toxicant for aquatic life, it should be used with great caution in agriculture to protect natural waters from contamination (Kӧprϋcϋ and Aydın, 2004).

Table 1 .
The mortality rate of A. bipunctatus exposed to acute commercial diazinon (21 fish for each concentration).

Table 2 .
The mortality rate of A. bipunctatus exposed to acute commercial deltamethrin (21 fish for each concentration).