Investigations of hemato-biochemical and histopathological parameters, and growth performance of walking catfish (Clarias batrachus) exposed to PET and LDPE microplastics

Effects of polypropylene microparticles ingestion on the growth and physiology of Piaractus brachypomus, and its accumulation and tissue damage

The presence of microplastics in aquatic environments is a growing concern due to their impacts on fish health. This study aimed to investigate the effects of different concentrations of polypropylene microparticles (PPMs) added to the diet of juvenile Piaractus brachypomus, on their growth, survival, physiology and tissue health. A total of 280 juveniles weighing 13.45 ± 2.07 g were divided into five treatments (0, 10, 100, 1000 and 5000 mg PPMs per kg of feed) with four replicates each. The juveniles were cultivated for 60 days in recirculating aquaculture systems. Biometrics and blood and tissue collections were performed after 10 and 60 days of the experiment. Juvenile performance was affected by the presence of PPMs in the diet within 10 days, with a reduction in final weight for the different concentrations. No differences were observed in juvenile growth after 60 days compared to the control. Total protein, hematocrit, and the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) changed significantly for the juveniles of the different treatments in both periods. No changes were observed in liver tissue histology; however, the presence of PPMs and damage to microvilli were verified in intestinal tissue. Although PPMs were observed in the intestine of juveniles in both periods, there was no migration of PPMs to the muscle. The addition of PPMs to juvenile diet caused growth disturbances within 10 days and blood and histological alterations in the intesine, without resulting in severe consequences leading to mortality in both periods.

Influence of Polystyrene Microplastics on Mitochondrial Oxidative Damage in Renal and Muscular Tissues of the Freshwater Fish

Polystyrene microplastics (PS-MPs), an emerging environmental contaminant, have attracted significant concern in recent years. This study aimed to evaluate mitochondrial oxidative damage in renal and muscular tissues of the freshwater fish Anabas testudineus following exposure to environmentally relevant concentrations (13.6 mg L⁻1 and 23.6 mg L⁻1) of PS-MPs for 1, 7, and 15 days. Exposure to PS-MPs disrupted the antioxidant defense system within the mitochondrial compartments of renal and muscle tissues, leading to increased levels of hydrogen peroxide generation and lipid peroxidation. PS-MPs exposure altered metabolic functions in the mitochondrial fractions of kidney and muscle tissues, as evidenced by elevated activities of alanine aminotransferase and aspartate aminotransferase. Besides, exposure to PS-MPs resulted in a decline of tissue-specific marker enzymes, such as acid and alkaline phosphatases, in renal tissue, indicating tissue damage. Histological examinations revealed significant tissue damage, including necrosis of renal tubules, vacuolization, glomerular degeneration, and melanomacrophage aggregation in kidney tissues. In muscle tissues, the observed damages included myolysis, vacuolar degeneration, necrosis, and atrophy of muscle fibers. These findings suggest that oxidative stress induced by PS-MPs exposure disrupts metabolic functions in mitochondrial fractions, thereby providing valuable insights into nephrotoxicity and muscular toxicity in fish.

Microplastics induce toxic effects in fish: Bioaccumulation, hematological parameters and antioxidant responses

This study investigates the toxic effects of microplastics by assessing bioaccumulation, hematological parameters, and antioxidant responses in juvenile Korean bullhead (Pseudobagrus fulvidraco) exposed to polyamide microplastics (PA-MPs). The increasing release of plastics into aquatic environments leads to their degradation into microplastics, which pose a significant threat to freshwater ecosystems. To evaluate these impacts, P. fulvidraco (mean length: 16.3 ± 1.1 cm, mean weight: 38.2 ± 6.6 g) were exposed to waterborne PA-MPs (white, spherical particles) at concentrations of 0, 10, 20, 5000 and 10,000 mg/L for 96 h. Bioaccumulation analysis revealed that PA-MPs primarily accumulated in the intestine, followed by the gills and liver. Hematological assessments showed significant reductions in hemoglobin and hematocrit levels at high PA-MP concentrations (5000 and 10,000 mg/L). Plasma biochemical analysis indicated significant alterations in calcium, magnesium, glucose, cholesterol, total protein, AST, ALT and ALP levels. In terms of antioxidant responses, superoxide dismutase (SOD) and catalase (CAT) activities increased significantly with PA-MP exposure, while glutathione S-transferase (GST) activity showed a marked decrease. These findings suggest that PA-MP exposure leads to bioaccumulation in key tissues and induces physiological stress in P. fulvidraco by altering hematological and antioxidant defense mechanisms, highlighting the potential toxicity of microplastics in freshwater fish.

An assessment of physiological and health responses in Catla catla fingerlings after polystyrene microplastic exposure

Microplastics (MPs) form when plastic debris is released into the aquatic environment, where they decompose and have deleterious effects on aquatic life. This study aimed to examine the harmful impacts of polystyrene MPs (PS-MPs) on the growth, carcass composition, hematology, digestibility, histopathology, and mineral analysis of Catla catla (11.09 ± 0.09 g/fish). Six experimental diets were prepared using canola meal (CM) as the base, each containing varying levels of PS-MPs: a control diet without MPs, and diets with 0.5%, 1%, 1.5%, 2%, and 2.5% PS-MPs. For ninety days, three groups of 15 fingerlings each were fed the test diets at a rate of 5% of their live, wet body weight. The growth rate and feed intake of C. catla fish showed a significant decline after the exposure to the diet containing 2.5% PS-MPs. Dietary inclusion of 2.5% PS-MPs resulted in reduced weight gain (g) and increased FCR. Mineral content and nutritional digestibility declined as PS-MP levels rose. PS-MPs led to a decrease in ash and protein content, while causing an increase in moisture levels and body fat. Moreover, exposure to PS-MPs resulted in significant reduction in RBCs, PLT, Hb, PCV, and MCHC, while WBCs, MCH, and MCV showed substantial increases. The histological analysis of the gut revealed elevated intestinal irregularities at 2.5% PS-MPs level. Notably, the present study revealed that PS-MPs accumulate in the gut, compromising the nutritional quality and overall well-being of C. catla fingerlings.

A review of the neurobehavioural, physiological, and reproductive toxicity of microplastics in fishes

Microplastics (MPs) have emerged as widespread environmental pollutants, causing significant threats to aquatic ecosystems and organisms. This review examines the toxic effects of MPs on fishes, with a focus on neurobehavioural, physiological, and reproductive impacts, as well as the underlying mechanisms of toxicity. Evidence indicates that MPs induce a range of neurobehavioural abnormalities in fishes, affecting social interactions and cognitive functions. Altered neurotransmitter levels are identified as a key mechanism driving behavioural alterations following MP exposure. Physiological abnormalities in fishes exposed to MPs are also reported, including neurotoxicity, immunotoxicity, and oxidative stress. These physiological disruptions can compromise the individual health of aquatic organisms. Furthermore, reproductive abnormalities linked to MP exposure are discussed, with a particular emphasis on disruptions in endocrine signaling pathways. These disruptions can impair reproductive success in fish species, impacting population numbers. Here we explore the critical role of endocrine disruptions in mediating reproductive effects after exposure to MPs, focusing primarily on the hypothalamic-pituitary-gonadal axis. Our review highlights the urgent need for interdisciplinary research efforts aimed at elucidating the full extent of MP toxicity and its implications for aquatic ecosystems. Lastly, we identify knowledge gaps for future research, including investigations into the transgenerational impacts, if any, of MP exposure and quantifying synergetic/antagonistic effects of MPs with other environmental pollutants. This expanded knowledge regarding the potential risks of MPs to aquatic wildlife is expected to aid policymakers in developing mitigation strategies to protect aquatic species.

Occurrence of microplastics in fish gastrointestinal tracts belongs to different feeding habits from the Bangladesh coast of the Bay of Bengal

The Bay of Bengal (BoB) is home to a range of commercially important species with different food habits and feeding features. Microplastic (MP) contamination in the fish of BoB, like in many other marine environments, is a significant environmental concern. The study aimed to investigate the presence of microplastics (MPs) in the gastrointestinal tracts (GITs) of selected commercial marine fishes from the Bangladesh coast of the BoB. Six fish species (Escualosa thoracata, Tenualosa ilisha, Johnius belangerii, Trichiurus lepturus, Planiliza parsia, and Mystus gulio) were investigated (n = 120) following hydrogen peroxide digestion, and floatation (saline solution) protocols. After analyses, a total number of 696 MPs (dimension 0.3 to 5 mm) were identified. Moreover, the highest occurrence of MPs in fish GITs was found in planktivorous fish (average of 7.7 items/individual), followed by omnivorous (average of 5.2 items/individual), and carnivorous fish (average of 4.6 items/individual) (p < 0.001). However, planktivorous E. thoracata showed the highest number of MPs per g of GIT (average of 30.99 items/g GIT), whereas T. ilisha showed the lowest count (average of 0.77 items/g GIT). Different types of MPs (fibers (19 to 76%), fragments (6 to 61%), films (8 to 35%), microbeads (0 to 5%), and foams (0 to 2%)) were also observed. In terms of the color of MPs, the transparent, black, green, and blue types were the most common. Polymers were found as polyethylene (35 to 43%), polyethylene terephthalate (28 to 35%), polyamide (20 to 31%), and polystyrene (0 to 7%). The study provides a significant incidence of MPs in fish from the Bangladesh part of the BoB, which is very concerning. Therefore, long-term research is indispensable to ascertain the variables affecting the presence of MPs in fish, their origins, and their potential effects on the BoB fisheries. Stringent policies on plastic use and disposal should be strongly urged in this coastal region.