Iranian Journal of Fisheries Sciences
Volume:23 Issue: 3, May 2024

The Na+-K+-ATPase (NKA) and Na+-K+-2Cl- cotransporter (NKCC) are the major ionic transporting proteins that regulate the secretion of chloride in marine bony fish. Their expression and activity are expected to increase with salinity. This study aimed to investigate the effects of salinity on the epidermal chloride cells of Periophthalmus waltoni to elucidate NKA and NKCC functions using immunohistochemistry method. For this purpose, 15 mudskippers (weight: 16.76±0.42 g, length: 16.62±1.10 cm, and water salinity: 38 g/L) that were collected from Mahshahr City were used. The fish were divided into three groups: FW group (with salinity of 1 ppt), BW group (15 ppt), and SW group (35 ppt) and treatment for two weeks. At the end of the experiment, the fish were collected, euthanized, and fixed in 4% paraformaldehyde for 24 h. Using specific antibodies, NKA and NKCC were localized in epidermal ion cells, and they were able to react to different salinity levels. The results of this study confirmed the model that states, NKA, and NKCC are responsible for the secretion of chloride from the chloride cells of bony fish.

A biological filter (biofilter) is a technique that aims to degrade nutrients that are wasted in water bodies by utilizing living organisms such as plants and shellfish. The study aims to determine the potential of duckweeds (Lemna minor)-freshwater mussel (Anodonta cygnea) integrated biofilters in utilizing nutrients from wastewater from rearing rainbow trout (Oncorhynchus mykiss) juveniles. This study used the initial weight of 25±2.0g of rainbow trout juveniles, freshwater mussels (A. cygnea) with an initial weight of 58±2.0 g, and duckweeds (L. minor) with two different biomass weights (treatment 1: 270 g and treatment 2: 360 g) were used in the flow-through system. The water temperature was around 13-14oC during the experimental periods. Using duckweeds as a biofilter with two different stocking densities significantly affected (p<0.05) the pH, DO, nitrate, and total phosphorus values in the treatment tanks. This study's results also revealed that using duckweed-freshwater mussels integrated biofilters could minimize the concentration of ammonium and total phosphorus in wastewater from rainbow trout juvenile rearing tanks.

Beyond aesthetics, the varied pigmentation in fish serves as evidence of manifold functions and has ecological importance. Fish pigmentation is an adaptive feature and critical to their survival. Despite their evolved pigmentation for survival and adaptation, fish are not immune to biochemical challenges presented by their surroundings. Harmful free radicals generated by various factors can lead to oxidative stress, impacting cellular components like pigments. Oxidative stress arises from an imbalance between the production of reactive oxygen species and cellular antioxidant defense mechanisms. Nevertheless, antioxidants play a role as crucial protectors, coordinating the defense of cells against oxidative damages. This review aims to elucidate the relationship between antioxidants and fish pigmentation by examining the sources of antioxidants in fish diets and their specific effects on pigmentation. The use of antioxidant compounds offers a promising avenue to mitigate pigmentation loss, enhance carotenoids production, and improve overall fish coloration, contributing to both aesthetic and physiological aspects in the aquaculture industry.

The study investigates the antimicrobial effect of two herbal essential oils, the leaves of Origanum vulgare and the bark of Cinnamomum verum, separately and in combination against S. iniae. The essential oils were extracted and their chemical composition was analyzed using gas chromatography-mass spectrometry. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the broth microdilution method. The fractional inhibitory concentration (FIC) method was employed to analyze the combined effect of the essential oils. The MIC of O. vulgare and C. verum against S. iniae were 0.976 mg/L and 100 mg/L, respectively, and the MBC value of oregano and cinnamon essential oils against S. iniae were 125 mg/L and 6400 mg/L, respectively. The FIC index was 0.625, which shows that the combined performance of the two essential oils is additive. The major compounds in Origanum and Cinnamomum essential oils were phenol-2-methyl-5 (1-methylethyl) (48.61%), thymol (16.76%) and cinnamaldehyde (64.5%), respectively. Overall, the results demonstrate that both essential oils exhibit antibacterial effects against S. iniae. In conclusion, the combined essential oils of O. vulgare and C. verum may hold promise as a novel antibacterial agent for the potential treatment and control of streptococcosis caused by S. iniae.

Sturgeon species are commercially important species in finfish aquaculture industry. Till now, a small number of studies have been reported on the immune responses in sturgeon species against infectious diseases. Monoclonal and polyclonal antibodies in fish immunoglobulins (Igs) are essential to evaluate the humoral immune response. This study aimed to produce, characterize, and evaluate the polyclonal antisera against stellate sturgeon Igs. For the production of polyclonal antibodies against fish Igs, stellate sturgeon serum Igs was isolated using the ammonium sulfate precipitation method. The purified Igs with the Freund adjuvant was injected subcutaneously in to sheep (Ovis aries). Then, anti- stellate sturgeon Ig antibody titer and specificity were determined using ELISA and Western blot techniques. Stellate sturgeon Ig antibodies were detected in the immunized animals and were significantly higher in the immunized group compared to the non-immunized group. The polyclonal antisera showed a high specificity to the immunoglobulin heavy )H( chain of stellate sturgeon and moderately cross-reacted with the immunoglobulin H chain in Siberian (Acipenser baerii) and ship (A. nudiventris) sturgeons but did not show reactivity with rainbow trout (Oncorhynchus mykiss) serum Igs. It was indicated that the produced polyclonal antisera should be further investigated to be used for immune-diagnostic purposes in sturgeon species upon exposure to various infectious diseases.

Sea cucumber Apostichopus japonicus lives in the lower temperature of the seawater and will enter the state of aestivation when the temperature is high. In recent years, the continuous high temperatures in summer have brought great loss to the production of sea cucumber in north China. To study the epigenetic regulating mechanism of A. japonicus and guide the temperature-controlled culture, the methylation level of A. japonicus genome was detected. Breeding imitation A. japonicus under different temperature conditions for a period of time, the difference of methylation level between the set temperature group and the control group was detected and verified. The methylation levels of A. japonicus in different temperature groups were detected. The methylation sites ranged from 84,766 to 96,225, and the sequencing depth was between 42.33 and 153.21. Under the temperature stress, more than 60% of the differentiated methylated genes in different groups were down-regulated, the HBW group had the most differentiated methylated genes (1,405), and the SBW group had the least differentiated methylated genes (643). Gene function classification and enrichment analysis were carried out, and a total of 3,512 differential genes were found, mostly related to immunity and metabolism. The results showed that temperature can change the gene methylation level of A. japonicus, affecting its expression level, and ultimately changing the metabolic and immune processes of A. japonicus.

Seasonal changes in the biochemical composition of Hemicentrotus pulcherrimus roe were analyzed from May 2016 to February 2017 in Korea. Spawning, occurring between April and May, was characterized by relatively low lipid (3.46 g/100 g) and protein levels (13.22 g/100 g). Concurrently, calcium level was increased, while magnesium level was decreased. The roe’s polyunsaturated fatty acids (PUFA) content was high, constituting 40% of total fatty acids, with eicosapentaenoic acid (C20:5n-3) and eicosatrienoic acid (C20:3n-3) being the most predominant. During the spawning season, lower levels of ascorbic acid (30.9 mg/kg) and folic acid were observed alongside higher concentrations of riboflavin (7.24 mg/kg) and niacin (232.32 mg/kg). Vitamin E content was at its lowest in May, measuring 0.05 mg/100 g, compared to a range of 1.62–2.22 mg/100 g in other seasons. Overall, the results suggest that H. pulcherrimus roe is a valuable source of protein, minerals, vitamins, and glycine, an important flavor component. However, significant variations in its biochemical components were noted during the spawning period compared to other seasons.

Prosopis species, particularly Prosopis juliflora are known for their antioxidant, anti-inflammatory, antibacterial, and antifungal properties. The present study evaluated the effect of three doses of dietary ethanolic leaf extract of P. juliflora (ELEPJ), i.e., 0.25, 0.5, and 1% on the immune- antioxidant system and the resistance to cold water stress in Pacific white shrimp, Litopenaeus vannamei. After 60 days of the feeding trial, the shrimps fed diets containing 0.5 and 1% ELEPJ showed significantly higher lysozyme activity, superoxide dismutase, phenol oxidase, and glutathione peroxidase than those of the control group (p<0.05). In response to the cold water stress, the shrimp fed diets containing 0.5 and 1% of ELEPJ showed significantly higher stress resistance than the control group. These results suggest the positive effects of ELEPJ on the immune-antioxidant system and stress resistance of L. vannamei and supplementation of 0.5-1% ELEPJ is recommended for the farm-raised shrimp diet.

The purpose of the current study was to ascertain the comparative effects of compounds, copper (II) oxide nanoparticles (nCuO) and copper salt (CuCl2), on the genotoxicity and histopathology of goldfish (Carassius auratus) for acute exposures of 24, 48, 72, and 96 h (concentrations: 100, 150, 200, and 1, 1.5, 2 mg/L nCuO and CuCl2, respectively). The peripheral erythrocytes were obtained for that purpose from the caudal vein in each individual. The Comet assay and micronucleus test were used to evaluate genotoxicity, and gill tissues were prepared for histopathology. High levels of nCuO and CuCl2 concentrations and acute exposure (96-hour) increased the percentage of DNA in the comet tails, olive tail moments, and micronucleus counts showed genotoxic effects on exposed fish. Also, the gill tissue alterations were observed and changed as the lifting of the respiratory epithelium, hyperplasia of the lamellar epithelium, incomplete, and complete fusion of several lamellae, and hypertrophy. Genotoxicity for nCuO and CuCl2 was discovered to be a concentration and time-dependent phenomenon. In general, experimental groups showed significant impacts (p=0.05) on concentrations and exposure periods, which may contribute to understanding the mechanism of nCuO and CuCl2-induced genotoxicity in the fish.

Thiazolidinones are heterocyclic organic medicines and the antifungal, antibacterial, and antiproliferative effects were shown in the studies. The aim of the study was to investigate the possible negative effects of (4S)-2-(4-hydroxy-3-methoxyphenyl)thiazolidine-4-carboxylic acid in zebrafish testicular tissue on an ultrastructural level. Experimental groups were exposed to different doses (0.2mM, 0.4mM, and 0.6mM) of thiazolidinone for 5 days. Further, no treatment was given to the control group. The testicular tissues were fixed and embedded in epoxy resin. The pathological sections were evaluated with transmission electron microscope. The sertoli, leydig, and spermatogenic cells of the control group showed intact morphology. In experimental groups, mitochondrial swelling, intense cristae loss, and autophagic vacuoles were observed in the Sertoli cells. Dilated perinuclear space, mitochondrial degeneration, and dilated smooth endoplasmic reticulum (sER) were detected in spermatocytes. The spermatids showed separation between genetic material and nuclear membrane. The condensation of genetic material was irregular. Mitochondrial degeneration and dilatation of sER tubules were detected. The Leydig cells showed perinuclear space dilatation, mitochondria degeneration, and dilatation in sER tubules. Our findings suggest that thiazolidinone has degenerative effects on zebrafish testis and this chemical should be carefully used in the pharmaceutical industry.