Adaptive Immune System in Fish

The immune system of all jawed vertebrates is composed of two major subsystems, the innate (non-specific) and adaptive (specific) immune system. The innate immune system is the first to respond to infectious agents; however, it does not provide longlasting protection. The adaptive immune system is activated later and responds to pathogens with specificity and memory. The main components of the adaptive immune system, including T cell receptors (TCRs), major histocompatibility complex (MHC), immunoglobulins (Igs), and recombination-activating gene (RAG) arose in the first jawed fish (cartilaginous and teleost fish). This review explores and discusses components of the adaptive immune system in teleost fish and recent developments in comparative immunology. Similar to mammals, the adaptive immune system in teleost fish is divided into two components: cellular-mediated responses and humoralmediated responses. T cells, the principal elements of cellular-mediated adaptive immune responses, differentiate into effector helper T (Th) cells or effector cytotoxic T cells (CTLs). The central elements involved in the differentiation of Th subsets in mammals, cytokines and master transcription factors, have also been identified in teleost fish. In addition, each subset of Th cells, defined with a particular cytokine to control the immune responses, has been described in teleost fish. Similarly, to mammals, CTLs contribute to cellular cytotoxicity in teleost fish. B cells act as a central player in humoral-mediated adaptive immunity by producing opsonizing, neutralizing and complement-binding antibodies and inducing antibody-dependent cellular cytotoxicity (ADCC). Three classes of antibodies named IgM, IgD, and IgT/Z have been characterized in teleost fish. The presence of an adaptive immune system and consequent immune memory in teleost fish allows vaccination, the most appropriate method for disease control in aquaculture. Immunological studies in fish provide a comprehensive assessment of the fish immune system, which is crucial for understanding the evolution of the mammalian immune system.

Preliminary Assessment of Microplastic Pollution Index: A Case Study in Marmara Sea

Marine litter is a crucial problem for marine environment, and this problem is generally based on anthropogenic activities. Even though human-induced activities that cause marine litter are well known, they have not been assessed for the microplastic pollution yet. Here, we present the Microplastic Pollution Index (MPI); a fast, convenient, inexpensive and semi-quantitative tool for assessing land- and marinebased pressures on the sampling area. In this preliminary study, MPI were determined for eight different locations in Marmara Sea. The Marmara Sea is under the effect of several pressures, which can be seen from MPI results. Furthermore, currents and coastline morphology affect the retention time of water at the coastal zone. The highest MPI values were obtained from the Izmit and Bandırma gulfs, whereas the lowest value was found at entrance of the Dardanelle Strait. MPI values and manta net abundance values for each station showed a good linear relation (R2 = 0.58; F = 7.113; DF =1, q = 0.045). No correlation was found between the water column and sediment abundance values. MPI is providing information on microplastic pollution, which is useful to create an effective monitoring strategy. Furthermore, environmental managers can use this information to combat, restore and protect coastal waters against the microplastic pollution.

Red tide of the Lingulodinium polyedrum (Dinophyceae) in Odessa Bay (Black Sea)

One of the most massive red tides at the Odessa Bay was observed in September October 2020. It was caused by a toxic dinoflagellate Lingulodinium polyedrum (Stein) Dodge. The maximum abundance (56.1 x 106 cells L-1) of L. polyedrum was registered at the Odessa port area on October 6 when a water temperature and a salinity were 19.7°C and 14.3 ‰ respectively. The red tide was so huge and dense that the water glowed at night due to the bioluminescence characteristic of this species. The article briefly describes the history of the study of L. polyedrum in this area and provides a detailed morphological description with original photographs of this species sampled from bloom. We associate the appearance of the red tide with an increased temperature of sea water and air, a high content of nutrients, the presence of viable L. polyedrum cysts, and a slight decrease in salinity in the bay during the period of a mass development of the species in autumn of 2020. The red tide was accompanied by Protoperidinium steini, P. divergens, Prorocentrum cordatum, P. minimum, P. micans, Gonyaulas scrippsae, Diplopsalis lenticula, Azadinium spinosum, Dinophysis rotundata, D. acuminata, Oblea rotunda, Scrippsiella trochoidea, Ceratium furca.

Spatio-Temporal Distribution and Characterization of Microplastic Pollution in The Three Main Freshwater Systems (Aksu and Köprü Streams, Manavgat River) And Fishing Grounds Located in Their Vicinities in The Antalya Bay

Microplastic pollution is one of the pressing environmental issues over the world that pose risks to aquatic ecosystems and humans. Significant amount of anthropogenic plastic litter known to be transported with freshwater systems to marine environment. The aim of the present study is to reveal the abundance and spatio-temporal distribution of MPs pollution in the three main freshwater systems (Aksu and Köprü Streams, Manavgat River), located through the costal line of the Antalya Bay. 106 water samples obtained from these three freshwater systems and fishing grounds located in the vicinities of these systems were evaluated. A total of 2444 MPs with a mean size of 1777.16±1168.81 µm detected within these samples. A homogeneous MPs pollution was observed in the area. Four colours (Black-27.3%, White-19.4%, Red18.7% and Blue-16.2%) found to composed more than 80% of the detected MPs. Majority of MPs detected within the framework of the study were fiber (57.1%) and fragment (32.6%). Most common polymer type was Polyproplene-(PP) with 50%. Results obtained from this study have the potential to form the basis for future studies that take into account the terrestrial use and the prevailing physical factors in the region in the study area.

Antioxidant Activity from the Enzymatic Hydrolysates of Chlorella sorokiniana and Its Potential Peptides Identification in Combination with Molecular Docking Analysis

Chlorella sorokiniana is an edible microalga known for its high protein content with a balanced amino acid composition, nutritional value, beneficial health effect, and natural antioxidant. The enzymatic assays was used to extract the peptides of C. sorokiniana which was an uncommon method to test the antioxidant activity. In this research, protein of C. sorokiniana was extracted, purified, and hydrolyzed in several enzymes and kept at 37°C for 16h. Hence, enzymatic hydrolysate <3kDA was fractionated into 11 portions (C0%, C10%, to C100%) by using offline Strong Cation Exchange Chromatography (SCX) and their antioxidant activity was tested using DPPH (2.2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The results indicated that C80%, contributed to the highest free DPPH scavenging on C. sorokiniana hydrolysate with the inhibition of 22.04%. Furthermore, to find the candidate peptides, this fraction was injected into LC-MS/MS for characterization of it's DPPH inhibitation. LSSATSAPS (m/z 1638,78) and AGLYGHPQTQEE (m/z 1328.59) are peptides that were identified and confirmed by LC-MS/MS. The molecular docking study was conducted to provide the binding simulation between these peptides and the ROS1 as the receptor. In conclusion, our results suggested that the aforementioned peptides were attached to ROS1 binding site and contributed to its potential antioxidant activity.

Assessment of Water Quality by Bioindication of Algae and Cyanobacteria in the Peshawar Valley, Pakistan

In purpose to assess the water quality in Peshawar Valley, the diversity of algae and cyanobacteria were studied in 41 sites during 2018-2019. A total of 361 species indicators of 7 Phyla were revealed. Algae and cyanobacteria in the studied sites preferred benthic and plankton-benthic lifestyle and mesotrophic waters. Indicators characterized water as moderate in temperature, medium oxygenated, low alkaline, and low saline. Algae and cyanobacteria inhabited medium-polluted and good water quality of Classes 2-3. The statistical maps were constructed for the first time to visualize the spatial distribution of diverse environmental and biological water quality variables and their relationship. The statistical maps and CCA revealed Water Temperature, Electrical Conductivity, Salinity, and Total Dissolved Solids as significant factors influenced freshwater algal and cyanobacteria communities. Statistical maps reflected an increase of dissolved substances from the foothills to the Kabul and Indus rivers' confluence. Acidification was revealed in the northeast of the valley. The bioindication results allowed us to propose that the algae and cyanobacteria communities were influenced by nutrient runoff from the surrounding foothills, agriculture, domestic and industrial effluents. The bioindication method combined with statistics can be recommended as a productive instrument for future water quality monitoring in the Peshawar Valley.

Quercetin Mitigates Oxidative Stress, Developmental Toxicity and Teratogenic Effects Induced by High-dose Vitamin D2 in Zebrafish Embryos

The aim of the study was to determine the developmental toxicity of high-dose administration of vitamin D2 (vit. D2) and the synergistic effect of vit. D2 inco-treatment with quercetin. Zebrafish embryos at 6 hpf were treated with either vit. D2 (1, 5, 10 μg/mL) or quercetin (5, 10 μg/mL) alone. The results from visual assessment and morphological feature scoring revealed, the occurrence of different morphological abnormalities spiked and aggravated with an increase in vit. D2 dose. The percentage of hatching, heartbeats/minute, velocity, body length, and survivability rate was downregulated in high dose vit. D2 groups. Subsequently, the production of proinflammatory cytokines and intracellular ROS was upregulated in high-dose vit. D2 groups. Contrastingly, in the co-treatment of vit. D2 (5 μg/mL) and quercetin (1, 5, 10 μg/mL), the occurrence of abnormal morphological characteristics was downregulated and the percentage of survivability rate was significantly increased. The production of inflammatory cytokines, intracellular ROS, and MDA was also observed to be inhibited in co-treatment groups. The important antioxidants such as glutathione and catalase were increased in co-treatment groups. The activity of S-A-β gal and apoptosis was downregulated in co-treatment groups. Collectively, quercetin ameliorated the developmental toxicity and teratogenic effects induced by high-dose vit. D2.

Rearing of White Leg Shrimp Litopenaeus vannamei (Boone, 1931) in Biofloc and Substrate Systems: Microbial Community of Water, Growth and Immune Response of Shrimp

The microbial composition of rearing water, growth and immune status of Litopenaeus vannamei juveniles in biofloc (T1), substrate-integrated biofloc (T2), substrate (T3) systems and a control with four replicates each were evaluated in a 49-day indoor trail. In each HDPE tank of 70 L capacity filled with 10 g L-1 salinity water, ten shrimp (4.56±0.13 g) were stocked. The C: N ratio of 15:1 was maintained in T1 and T2 using wheat flour as carbon source for production of biofloc. The TAN, NO2 and NO3 were lower (P<0.05) in treatment tanks than that in control. It was also observed that the counts of Bacillus, Lactobacillus, Vibrio and zooplankton were high in T2 than T1, T3 and control. There was higher net weight gain (10.38±0.14 g) and lowest FCR (1.27±0.12) with T2 when compared to T1, T3 and control tanks. Moreover, the survival rate is significantly higher in treatments than control. Significant increase in THC (47.24±4.49 x 106 cells ml-1), serum protein (82.67±0.01 mg/ml), Phenoloxidase (0.73±0.03, OD 490 nm) and Lysozyme activity (56.32±0.03%) was observed in T2 than T1, T3 and control. The result shows that substrate-integrated biofloc system assures higher growth, survival and better immune response in L. vannamei.

Plastic Occurrence in Commercial Fish Species of the Black Sea

The occurrence of micro- (<5 mm), meso- (5–25 mm) and macroplastics (>25mm) was investigated in seven commercial fish species of the Black Sea. Plastics were found in gastrointestinal track of all species analysed: Engraulis encrasicolus, Trachurus mediterraneus, Sarda sarda, Belone belone, Pomatus saltatrix, Merlangius merlangus and Mullus barbatus. A total of 352 plastic particles were removed from 190 individuals (29% of all individuals examined). The mean number of plastic particles per fish was 0.81±1.42 par.ind-1 (considering all fish analysed, n=650) and 2.06±1.09 par.ind-1 (considering only the fish that ingested plastic, n=190). The most common types of plastics were fibres (68.5%), followed by films (19%), fragments (11.9%), foams (0.3 %) and microbeads (0.3%). The most common plastic colour was black (39.3%) followed by blue (19.5%) and transparent (18.1%). The length of plastics ranged from 0.05 to 26.5 mm with an average of 1.84±2.80 mm. 93.2% of plastics were microplastics, 6.5 % as mesoplastics and 0.3% macroplastics. Plastic occurrence was higher in S. sarda (plastic in 70% of the analysed individuals) and lower in M. merlangus (plastic in 9% of the analysed individuals). The main synthetic polymers identified by Fourier-transform infrared (FTIR) spectroscopy were polypropylene (29.8%), polyester (17.5%), acrylic (15.8%), polyethylene (14%) and polystyrene (1.8%) and 21.1% of polymers were cellulosic. Results show that commercial fish of the Black Sea is contaminated by plastics. This might affect vital functions of fish and pose a risk to ecosystem and human health. The study contributes to a better understanding of the status of plastic pollution in the fish from different habitats of the Black Sea and provides baseline data to implement the Marine Strategy Framework Directive in the basin.

Transcriptome Analysis of Immune Response Process in Yellow Catfish (Pelteobagrus fulvidraco) During Edwardsiella tarda Exposure

Edwardsiella tarda, the causative agent of ascites disease, is a major fish pathogen and has caused significant economic losses in aquaculture. To decipher the immune response process challenged by E. tarda in yellow catfish (Pelteobagrus fulvidraco), the transcriptomic profiles of the spleens infected with bacteria at 6 h, 24 h, and 72 h were obtained using the Illumina sequencing platform. After de novo assembly, a total of 158,124 unigenes were detected. To further investigate the immune-related DEGs, gene ontology (GO) enrichment and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis were performed. Immune pathways about antigen processing and presentation pathway, complement and coagulation cascades pathway, and apoptosis pathway were combined to discussed in this study. Additionally, 10 immune-related DEGs in these three immune pathways were randomly selected for expression verification by quantitative Real-time PCR (qRT-PCR). The data generated in this study provides a valuable resource for further immune response research and offers efficient strategies against E. tarda infection in yellow catfish.