Evaluation of the haematological parameters in Piaractus mesopotamicus Holmberg (Osteichthyes, Characidae) with Argulus sp. (Crustacea, Branchiura) infestation and treatment with organophosphate

Abstract

Haematological parameters as elythroeytes, leukocytes and plasma glucose in Piaraclus mesopolamicus Holmberg, 1887 were analyzed. Fish were parasitized with Argulus sp. (Crustaeea, Branchiura) and treated with 0.4 mg of thric1orphon 500/L water. The effects of parasitism and the aetion of the treatment were evaluated. Parasitized fish showed greater number of monocytes (P>0.05) and speeial granuloc itic cells (P 0.05). Organophosphate treatment presented signifieantly reduction (P>0.05) in red blood eells (RBC) and hemoglobin. KEY WORDS. Piaraclus mesopolamicus, Argu/us, parasitism, haemathology Haematological studies on Brazilian fishes associated to the parasitism in culture system (RANZANI-PAIVA et aI. 1987) or in the nature (RANZANl-PAIVA et aI. 1997) are rarely observed. ln the present study, the authors compare the effects ofthe natural parasitism with Argulus sp. (Crustacea:Branchiura) and the response to the organophosphate treatment. Comparison was performed on treated and untreated pacu Piaraclus mesopolamicus Holmberg, 1887. Ten fish with 215.0 ± 39 g ofbody weight and 19.8 ± 1.1 cm oflength, were collected from a pond at Aquaculture Center-CAUNESP, laboticabal, São Paulo State, Brazil. Fish presenting the crustacean Argulus sp. on their body, were maintained in a 250-litter aquarium. The ranges oftemperature, pH, electric conductivity, and dissolved oxygen were between 27 .3 and 28.0°C, 7.5 and 7.6, 186.0 and 190.0 IlS /cm and 4.0 and 4.1 mg/L, respectively. Fish were submitted twice to OA mg of thriclorphon 5001L ofwater within a two-day interval. ln the fifth day, with the aid of a syringe containing EDTA (10%), I mi ofthe blood was collected from the caudal vein.