Exposure to polypropylene microplastics via diet and water induces oxidative stress in Cyprinus carpio.

The occurrence of accumulation of microplastics in humans and wildlife has become a serious concern on a global scale, especially in the last decade. Although there are many studies on microplastics, their biological effects and toxicity on freshwater fish have not been fully revealed. In order to evaluate the potential toxic effects of PP (polypropylene) microplastics in freshwater fish, we performed 1-day, 2-day, 3-day, 4-day, 5-day, 6-day, and 7-day microplastic exposure to different concentrations of the microplastics through water and diet on Cyprinus carpio. Fish samples were divided into 3 groups; Group-A with different PP microplastic concentrations in their water (ALow:1.0 g/L and AHigh:2.5 g/L), Group-B with different PP microplastic concentrations in their diet (BLow:100 mg/g and BHigh:250 mg/g), and Group-C (Control group) free of PP microplastics in their diet and water. The results showed that although microplastics did not cause death in C. carpio, they caused oxidative stress in comparing the MP exposed groups to the control groups. When indices of oxidative stress of fish individuals in all treatment groups were compared with the control group, it was determined that MDA (malondialdehyde) and GSH (glutathione) levels increased, while TPC (total protein content) and CAT (catalase) levels decreased depending on the concentrations and exposure times. Significant differences were observed between the control and treatment groups in the indices of oxidative stress (P<0.05). This study provided basic toxicological data to elucidate and quantify the effects of PP microplastics on freshwater fish. In addition, this study is the first study to indicate that microplastic exposure of carp via diet and water causes oxidative stress in gill tissues and causes changes in CAT, MDA, GSH, and TPC levels. The findings also provide useful reference data for improving knowledge of the effects of microplastics on organisms in freshwater systems.

Morphologic, morphometric and contour shape variations of sagittal otoliths of Lepidorhombus spp. in the Aegean Sea.

Otoliths are calcareous anatomical structures in the inner ear of fishes, and they can be used in the discrimination of fish species and stocks due to their species-specific shape. Sagittal otoliths in the Lepidorhombus whiffiagonis and Lepidorhombus boscii, two flatfish species of the same genus distributed in the Aegean Sea, were compared using morphology, morphometry and contour shape analyses. Blind and eyed side otoliths of Lepidorhombus species were evaluated separately due to their morphological features and statistical differences in morphometric measurements (p < 0.05). Four analysis groups were formed: blind side otolith of L. whiffiagonis, eyed side otolith of L. whiffiagonis, blind side otolith of L. boscii and eyed side otolith of L. boscii. Morphometric differences in otolith shape were performed by canonical discriminant analysis, and the first discriminant axis explained 97.4% (Wilks λ = 0.270) of the variance between the groups, and the second axis explained 2.3% (Wilks λ = 0.620). Classification success between Lepidorhombus species based on CDA is 100%, and the overall CDA classification score between groups is 76.5%. The wavelet functions obtained in the contour analysis showed high variability in the anterior, posterior-dorsal, antero-dorsal and ventral regions of the otoliths among these four analysis groups. Consequently, it is thought that this study will contribute to the taxonomic classification of fish with the morphological and morphometric differences in the blind and eyed side otoliths and the analyses made with the high discrimination success obtained in Lepidorhombus species.

Morphological and morphometric features of the abnormal and normal saccular otoliths in flatfishes.

The fish's inner ear consists of three interconnected semicircular canals and otolith organs located in these canals, which are responsible for balance and hearing. Abnormalities in these organs can affect the vital activities of the fish. The main purpose of this study was to determine the morphological and morphometric characteristics of abnormal and normal sagittal otoliths in the four flatfish species (Lepidorhombus boscii, Platichthys flesus, Solea solea, and Pegusa lascaris) sampled from three seas (Aegean Sea, Mediterranean Sea, and Black Sea). Abnormalities in otoliths are investigated using light microscopy, scanning electron microscopy, and Raman spectroscopy. The otolith morphometric measurements and morphology are recorded for abnormal and normal otoliths for each species. It was determined that the four flatfish species examined in the present study showed differences in the morphological features of normal and abnormal otoliths in the blind and eyed sides. In addition, statistical differences were observed when the weight, length, width, perimeter, and area values of normal and abnormal otoliths of all species were compared (p < .05). The four types of saccular otoliths were defined, one normal (type 0) and three abnormal (type 1, type 2, and type 4) for four flatfish species. The current study presents for the first-time abnormal otolith morphology information on blind and eyed side sagittal otoliths in these flatfish species. Abnormalities in the anatomical structures of bony parts such as otoliths in fish may be caused by pollution, nutritional problems, stress, and environmental factors as well as a combination of these.

Sagittal otolith morphology of sharpsnout seabream Diplodus puntazzo (Walbaum, 1792) in the Aegean Sea / Morfología de los otolitos sagitales del sargo picudo Diplodus puntazzo (Walbaum, 1792) en el Mar Egeo

The morphology, biometry and shape indices of the left and right sagittal otoliths were studied for sharpsnout seabream, Diplodus puntazzo species from Aegean Sea. The shape, sulcus acusticus shape, proximal and distal surfaces, anterior and posterior regions of left and right sagittal otoliths for a total of 52 D. puntazzo were analyzed. The morphometric measurements such as weight, length, width, area and perimeter were recorded for each pair of sagittal otoliths of the sharpsnout seabream. The shape indices such as form factor, roundness, aspect ratio, circularity, rectangularity, and ellipticity were calculated for left and right sagittal otoliths of D. puntazzo. The otolith width and ellipticity were significantly different (P <0.05) for left and right sagittal otolith measurements and shape indices, respectively in D. puntazzo inhabiting the Aegean Sea. Morphological characteristics of fish otoliths were highly variable in species and populations; there was limited information on the sagittal otolith morphology and shape indices. The present study provided sufficient information of the sharpsnout seabream left and right otolith morphologies, biometry, and shape indices in the Aegean Sea, they may provide a useful tool for marine and freshwater species discrimination and identification in further investigations.

Los índices morfológicos, biometría y la forma de los otolitos sagitales izquierdo y derecho se estudiaron para la especie sargo picudo, Diplodus puntazzo del mar Egeo. Se analizaron en 52 D. puntazzo la forma del surco acústico, las superficies proximal y distal y las regiones posteriores de los otolitos sagitales izquierdo y derecho. Además, se registraron para cada par de otolitos sagitales las mediciones morfométricas de peso, longitud, ancho y perímetro. Se calcularon en ambos otolitos sagitales los índices de forma, factor de forma, relación de aspecto, circularidad, ortogonalidad y elipticidad. En el D. puntazzo que habita en el mar Egeo, el ancho y elipticidad de los otolitos fueron significativamente diferentes (P <0,05), para las mediciones de otolitos sagitales izquierdo y derecho, respectivamente. Existen gran variabilidad en las características morfológicas de los otolitos de diferentes especies y poblaciones de peces, asimismo es limitada la información de los índices morfológicos y la forma de los otolitos sagitales. El presente estudio proporciono información suficiente sobre la morfología y biometría de los otolitos izquierdo y derecho del sargo picudo en el Mar Egeo, lo que puede proporcionar una herramienta útil para la discriminación e identificación de especies marinas de agua dulce y para nuevas investigaciones.