Effect of parasitic infection on microplastic ingestion in a native leuciscid hybrid species (Alburnus derjugini x Squalius orientalis) from Kürtün Dam Lake, Türkiye.

Microplastic (MP) pollution is currently one of the most serious environmental issues. MPs were investigated in the Kürtün Dam Lake in healthy individuals of the native leuciscid hybrid (Alburnus derjugini x Squalius orientalis) species and individuals infected with the Ligula intestinalis parasite. Although MP abundance appeared to be higher in non-infected fish (NIF) than in L. intestinalis (L) and infected fish (IF), the MP abundance in IF was higher, because the parasite theoretically belongs to IF. In addition to the observation of MPs in the gastrointestinal tract (GIT) of fish, the diffusion of MPs by parasites settled in the body cavity indicates that MPs are not only present in the GIT. Therefore, predation on existing fish by birds causes MP dispersion. In the present study, the most common MP shape was fiber (100% for NIF and IF, 85.7% for L), the MP color was black (57.1% for IF and L) and orange (50% for NIF), and the polymer type was polyamide (57.1% for IF, 50% for NIF) and polyethylene terephthalate (28.5% for L). These MP compositions led us to believe that textile effluents and aquaculture operations in dam lakes could be sources of pollution. Therefore, this study provides insights for future research to elucidate the connection between MP consumption and parasite infection.

Determination of the use of Ligula intestinalis as a bioindicator in malathion residues.

In this study, the usability of Ligula intestinalis as a bioindicator for pesticide accumulation was investigated. Two different experiments were designed for the detection of pesticide residues and its withdrawal period. In the first experiment, the accumulation of malathion for 10 days was measured in the hybrid fish, Squalius orientalisxAlburnus derjugini sampled from a dam lake. In the next experiment, withdrawal was measured for 15 days. The infected and healthy fish in groups exposed malathion and not exposed malathion were sampled at the end of the first experiment. No malathion residue was found in the control group that was not exposed with malathion. For the second experiment, infected and healthy fish from malathion and without malathion groups were sampled to measure the elimination of malathion on the 1st, 4th, 5th, 8th, 12th, and 15th days. At the end of the first experiment, the presence of malathion was not detected in the control group while accumulation was observed in both fish and L. intestinalis in the experimental group. At the end of the second experiment (15th day), the highest residual value was found in L. intestinalis (1.02 mg/kg) while it was determined as 0.009 mg/kg in infected fish and 0.006 mg/kg in uninfected fish. According to the correlation, malathion accumulation was linear between uninfected fish and infected fish. On the other hand, an inverse correlation was found between L. intestinalis and both malathion and control fish. As a result, it was determined that L. intestinalis can be used as a bioindicator in pesticide accumulation and the pesticide is still detectable in the parasite after withdrawal from fish.

Assessment of hematological indicators, histological alterations, and DNA damage in Danube sturgeon (Acipenser gueldenstaedtii) exposed to the organophosphate malathion.

This study focused on organophosphate malathion toxicity in Danube sturgeon (Acipenser gueldenstaedtii) and its negative effects in sub-lethal concentration. In this context, the LC50 value of fish exposed to five different concentrations and two different sub-lethal concentrations depending on the LC50 value were considered. Accordingly, LC50 of malathion for 96 h was 3.24 mg L-1. In leukocyte (WBC) and hemoglobin (HGB) such as hematological indicators, significant differences were observed in sub-lethal concentration (One-eighth of the LC50 =0.4 mg L-1). In addition, serious histological alterations were observed in the gill and liver tissues after both acute (96 h) and chronic periods (28 days). While epithelial lifting and hyperplasia were the most prominent lesions in the gill, intense vacuolization were observed in the liver. In addition, circulatory disturbances, regressive changes, and progressive changes in the gill and circulatory disturbances and inflammation in the liver were significantly higher for the chronic period. Finally, significantly higher DNA damage was detected in fish exposed malathion in the chronic period compared to the control group. In conclusion, the present study has proven that malathion has a hematological, histological and genotoxic effect on the endangered species A. gueldenstaedtii. Thus, the current study will motivate for residue studies on A. gueldenstaedtii and trigger conservation strategies for local governments.

Investigation of long-term bisphenol A exposure on rainbow trout (Oncorhynchus mykiss): Hematological parameters, biochemical indicator, antioxidant activity, and histopathological examination.

As an industrial synthetic chemical, bisphenol A (BPA) has the potential to have physiologically and histologically adverse effects on aquatic organisms. BPA causes the reproductive disrupting of all vertebrates due to its degradation on endocrine system. Therefore, the effect of BPA on fish with high economic value is an important issue. This study focused weekly on long-term BPA exposure on rainbow trout (Oncorhynchus mykiss). Hematological, biochemical, antioxidant activity and histopathological examinations were performed on O. mykiss exposed to 1000 µg/L BPA concentration. Mortality was observed in the BPA group during the first three weeks. As a result of hematological studies, leukocyte count and hemoglobin in the BPA group were significantly higher in the first three weeks compared to the control group. Plasma cortisol level as a biochemical indicator showed a similar trend to leukocyte and hemoglobin. There was no significant difference between BPA and control groups in terms of superoxide dismutase and catalase. However, glutathione peroxidase activity in the BPA group was significantly lower than in the control group for four weeks. At the end of the study, many alterations were observed histologically in the gill tissues. While more intense hyperplasia and epithelial lifting were observed in the tissues in the BPA group compared to the control group, vacuolization, necrosis and hypertrophy were observed infrequently. In conclusion, this study argues that BPA causes negative effects on O. mykiss in terms of fish welfare and future study should be focused on its environmental adaptation with color preference patterns.