The effect of Goezia leporini Martins & Yoshitoshi, 2003 (Nematoda: Anisakidae) infection on the haematological characteristics of cultivated Leporinus macrocephalus (Osteichthyes:Anostomidae) was studied. Paleness of gills, kidneys, liver and heart, black spots on the kidney and accumulation of fluid in the visceral cavity, stomach and intestines were observed. Gall bladder content had pale and translucent aspect. Strong and slight positive correlations between number of nematodes and fish weight were estimated within the 0-100g and 100-200g fish weight group, respectively. Blood smears from infected fish showed variation in erythrocyte size (anisocytosis) and shape (poikilocytosis), and also dividing erythrocytes. No significant alteration (P>0.05) was shown as to erythrocyte, leukocyte count, haemoglobin concentration and thrombocyte and monocyte percentage. Parasite infection provoked significant reduction (P<0.05) in hematocrit, mean corpuscular volume, mean corpuscular haemoglobin concentration and lymphocyte percentage. On the other hand, significant increase (P<0.05) in neutrophil and eosinophil percentage in circulating blood of infected fish was observed. This is the first report regarding haematology of nematode infected freshwater cultivated fish in Brazil.Keywords: Brazilian fish, piauçu, Leporinus macrocephalus, Nematoda, Goezia leporini, haematology RESUMO Estudou-se efeito da infecção por Goezia leporini
ABSTRACT. This work is a sequence of studies on tropical fish of economic importance that evaluated the effects of two different stress of handling on the physiology and haematology of Oreochromis niloticus L. acclimated for 10 days before the essay. The stress consisted in net capture of all fish from each aquarium for 30s emersion. Fish exposed to single stress (SS) the samples were collected in the times 0, 10, 20, 30, 40, 50, 60, 120, 180, 240 and 300min. after stress. In the consecutive stress (CS) the samples were collected in the times 0; 15min. after the first stress; 15min. after the second stress; 15min. after the third stress and 15, 30, 45, 60, 120, 180 e 240min. after the fourth stress totalizing four stimuli every 60min. Fish exposed to SS showed increased cortisol and glucose concentrations at 60min. as well as in the leucocytes number and hematocrit at 50min. after stress. Cortisol did not alter in fish exposed to CS, but glucose increased 15min. after the third stress. On the other hand, CS provoked reduction in the leucocytes number and later hematocrit increasing. Neutrophilia and lymphopenia were related to SS and CS.Key words: Oreochromis niloticus, consecutive stress, cortisol, glucose, haematology. RESUMO. Resposta fisiológica e hematológica de Oreochromis niloticus (Osteichthyes:Cichlidae) exposto ao estresse único e consecutivo de captura. Este trabalho é seqüência de estudos com peixes tropicais de importância econômica avaliando os efeitos de dois tipos de estresse sobre a fisiologia e hematologia de O. niloticus L, aclimatados durante 10 dias antes do experimento. O estresse consistiu na captura de todos os peixes do aquário com rede e emersão por 30 s. Nos animais submetidos ao estímulo único de captura (EU) as amostras foram coletadas nos tempos 0, 10, 20, 30, 40, 50, 60, 120, 180, 240 e 300min. após o estresse. No estímulo consecutivo (EC) as amostras foram coletadas nos tempos 0; 15min. após o primeiro estresse; 15min. após o segundo estresse; 15min. após o terceiro estresse e 15, 30, 45, 60, 120, 180 e 240min. após o quarto estresse totalizando quatro estímulos a cada 60min. Os peixes expostos ao EU apresentaram aumento nas concentrações de cortisol e glicose 60min., bem como no número de leucócitos e hematócrito 50min. após o estresse. Não houve alteração do cortisol nos peixes do EC, mas a glicose aumentou 15min. após o terceiro estresse. Por outro lado, o EC provocou redução no número de leucócitos e aumento tardio do hematócrito. Observou-se neutrofilia e linfopenia após o EU e EC.
Columnaris disease is one of the main causes of mortality in tilapia rearing and is responsible for large economic losses worldwide. Hematology is a tool that makes it possible to study organisms' physiological responses to pathogens. It may assist in making diagnoses and prognoses on diseases in fish populations. The hematological variables of nile tilapia were studied in specimens with a clinical diagnosis of columnaris disease and in specimens that were disease-free. The total erythrocyte count, hemoglobin rate, hematocrit percentage, mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), mean corpuscular volume (MCV), organic defense blood cell percentages (leukocytes and thrombocytes) and hepatosomatic and splenosomatic index were determined. The results showed that there were changes in the erythrocytic series and in organic defense blood cells, in the fish infected with the bacterium, with reductions in erythrocytic variables and significant increases in the numbers of circulating lymphocytes and neutrophils.
Macrophytes are important for aquatic biocenosis, however under certain conditions its population can raise becoming a problem in reservoirs, such as the Egeria densa. To control these plants, CONAMA discuss for the use of chemicals, but feasibility and safety studies should be conducted to allow the use for such purpose. Thus, the present study evaluated the effects of decomposition of Egeria densa killed by the herbicide diquat on water quality variables and physiological responses of Nile tilapia. Thus, 176 tilapias were distributed in 16 tanks and submitted to four treatments (tilapia without macrophyte; tilapia and macrophyte; tilapia and macrophyte died by diquat; and macrophyte died by freezing). The values of pH, temperature, dissolved oxygen, alkalinity and conductivity did not differ between treatments. However, an increase in total ammonia and phosphorus and reduction of nitrite concentrations in treatment with macrophyte killed by the herbicide was observed. Chlorophyll-a concentration did not differ between treatments, however, phaeophytin-a increased in water submitted to plants died by freezing. After 21 days of experiment, no differences were observed in blood glucose, cortisol, leukocytes, erythrocytes and hemoglobin. Thus, tilapia does not alter their physiological patterns after chronic exposure to decomposing macrophytes killed by diquat.
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