Effects of exposure to a therapeutic level of methylene blue on antioxidant capacity, haemato‐immunological responses and resistance of goldfish,Carassius auratustoAeromonas hydrophila

Abstract

Methylene blue (MB) can have inhibitory effects against protozoan and fungi in fish. In this investigation, fish were first exposed to different MB concentrations (0 and 2 mg L−1) for 21 days. Then, the fish were challenged with Aeromonas hydrophila for 7 days. Some haemato‐immunological and biochemical parameters, oxidative stress biomarkers in blood, growth performance and fish resistance to A. hydrophila were examined once a week. The results showed that erythrocyte, haemoglobin, leucocytes, haematocrit, mean corpuscular volume., mean corpuscular haemoglobin concentration and lymphocyte percentage significantly reduced in the fish after exposure to 2 mg L−1 MB on the 14th and 21st days and challenged period on 28th day. Although the superoxide dismutase, catalase, and glutathione peroxidase, lysozyme, phagocytic activities and a quantitative nitroblue tetrazolium, total protein and cellular total antioxidant levels in the serum decreased significantly, the percentage of neutrophils, aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase activities increased significantly in fish exposed to 2 mg L−1 MB (p < 0.05). There was a significant difference in the growth performance and the percentage of monocytes exposed to 2 mg L−1 of MB compared to the reference group. The mortality rate was declined in the treated fish with 2 mg L−1 of BM after challenge with A. hydrophila compared with the control group. Overall, the present results indicate some negative impacts of MB application in goldfish even at the therapeutic level. From these, the immunosuppressive effects of MB may be potentially disruptive for a health condition.

Toxicity of common biocides used in aquaculture to embryos and larvae of Brachymystax tsinlingensis Li

“…The acute toxicity of Cu, Zn and MB to fish varies based on species and life stage (Calfee et al ., 2014; Hansen et al ., 2002; Olufayo & Yusuf, 2016; Soltanian et al ., 2021; Vardy et al ., 2013; Xin et al ., 2015). For example, the LC 50 values at 96 h for copper and zinc to Puntius parrah were 0.51 and 8.46 mg l −1 , respectively; in contrast with 0.048 and 0.6 mg l −1 for Atlantic salmon ( Salmo salar ) (Ciji & Bijoy Nandan, 2014; Sprague, 1964).…”

“…Olufayo and Yusuf (2016) assumed that MB, which is widely used as a biocide in the treatment of algae and cyanobacteria, is safe for use with fish eggs and fry for the prevention of fungal infections and was effective in reducing the bacterial load in tilapia ( Orechromis niloticus ) fingerlings (Bolivar et al ., 2012). Nonetheless, copper, zinc and MB may adversely affect various physiological processes in developing fish, resulting in higher mortality, developmental retardation, morphological and functional deformities and aberrant behaviour (Akbary et al ., 2018; Jiang et al ., 2015; Kousar & Javed, 2015; Saibu et al ., 2018; Soltanian et al ., 2021). The effects of metals on various fish organs, tissues and metabolic processes are related to osmotic disturbances and alterations in enzyme synthesis and activity (Barbara et al ., 2009; Sfakianakis et al ., 2015), which can have lethal effects on the survival of aquatic animals.…”

Toxic Effects of Methylene Blue on the Growth, Reproduction and Physiology of Daphnia magna

“…Perlberg et al [ 13 ] found that MB was teratogenic to Pterophyllum scalare , reporting that exposure to a 5 ppm concentration resulted in a higher incidence of non-inflatable swim bladders. In contrast, Soltanian et al [ 14 ] found that goldfish ( Carassius auratus ) exposed to a 2 mg/L solution of methylene blue for 21 days had significantly reduced lethality caused by Aeromonas hydrophila . However, the fish also exhibited significantly lower levels of neutrophils and aspartate aminotransferase, indicating some immunosuppressive effects and potential harm to their health.…”

Development of water-soluble phenazine-2,3-diol-based photosensitizers for singlet oxygen generation

“…Moreover, for use in water purification systems and PDT, the PSs are required to possess high solubility in water as well as efficient ISC. Methylene blue ( MB ), 9 Rose Bengal ( RB ), 10 and hydrophobically modified porphyrin derivatives 11 have been used as water-soluble PSs with high 1 O 2 Φ Δ values (0.50–0.60 for MB , 9 b,c 0.70–0.80 for RB , 9 b ,10 b and 0.50–0.60 for free base 5,10,15,20-tetrakis(4-carboxylatophenyl)porphyrin, 11 a,b respectively). Meanwhile, halogen atoms such as iodide and bromide atoms are often introduced into chromophores ( e.g.…”