Veterinary Research Forum

Abstract Streptococcus agalactiae is a Gram-positive bacterial pathogen accountable for disease outbreaks in tilapia, resulting in substantial economic losses in aquaculture. In this study, a 10-round whole-cell Systemic Evolution of Ligands by Exponential Enrichment procedure was conducted to isolate and characterize single-stranded DNA aptamers with specific binding affinity to S. agalactiae. The enriched single-stranded DNA libraries were sequenced by high-throughput sequencing, yielding a total of 180,987 reads, of which 126,933 included unique aptamer sequences. The most frequent sequences were selected for further analysis. Among them, SA1 had the highest frequency, with 231 reads, whereas SA2 showed a lower number of 16 reads. These findings underscored the validity of combining whole-cell Systemic Evolution of Ligands by Exponential Enrichment, high-throughput sequencing and aptamer-structure analysis to explore the interaction between aptamers and bacterial cell surfaces. The selected aptamers not only showed promise for the detection of S. agalactiae but also served as molecular probes for identifying surface-exposed proteins, studying host-pathogen interactions and guiding targeted drug delivery in aquaculture-related applications.

Abstract This study investigated the antioxidant and apoptotic systems of blue swimmer crabs at various reproductive stages, providing valuable insights into their potential as biological markers, particularly in the polluted Persian Gulf. Our research along the coasts of Hendijan County, Iran, involved capturing live crabs (167 ± 52.07 g), examining their morphological traits and determining their reproductive stages through dissection and histological analysis. Apoptosis was detected using the TUNEL assay (terminal deoxynucleotidyl transferase dUTP nick end labeling), and enzyme activities including superoxide dismutase, catalase and glutathione peroxidase were measured using colorimetric methods. Variations were observed in the abundance of apoptotic cells within the hepatopancreas across reproductive stages. The second stage exhibited the lowest values and the first stage displayed the highest indicating a potential link between reproductive activity and apoptosis. Furthermore, enzymes representing the antioxidant system demonstrated various activities during ovarian development. Notably, the second ovarian stage demonstrated the highest catalase (5.63 mM per g protein) and malondialdehyde (12.14 mM per g protein) activities indicating an elevated response to oxidative stress. Our findings demonstrated that apoptotic cell numbers were fluctuated throughout the reproductive stages in the crabs, with the highest levels observed during the first stage and the lowest during the second stage. Understanding these fluctuations not only aids in distinguishing between reproductive and non-reproductive phases but also offers valuable insights into the broader physiological changes occurring throughout the cycle.

Abstract The natural polymer poly-β-hydroxybutyrate (PHB) is converted to β-hydroxybutyric acid, which is similar to short-chain fatty acids, via microbial fermentation and host enzyme breakdown. This study investigated the impact of different PHB concentrations (Control, 1.00, 3.00, and 5.00% substitution) on growth performances and fish welfare in common carp fingerlings. After a 60-day trial, fish fed on diet containing 1.00% PHB exhibited significantly higher weight gain and improved feed conversion efficiency compared to the control group. Furthermore, analysis of enzymatic activity showed elevated levels of total protease and amylase in PHB-fed treatments compared to the control. Red blood cell counts, hemoglobin, and hematocrit levels remained unaffected and a significant increase in white blood cell count was observed in fish fed on diets containing 1.00 and 3.00% PHB compared to the control group. Furthermore, fish fed on diets containing 1.00 and 3.00% PHB demonstrated significantly higher total protein levels and lower glucose concentrations as well as reduced hepatic enzyme activities (aspartate aminotransferase and alanine aminotransferase) compared to both the control and 5.00% PHB groups. Assessment of antioxidant and immune parameters revealed significantly increased complement hemolytic activity and immunoglobulin M levels coupled with decreased malondialdehyde concentrations in the plasma of PHB-fed fish compared to the control group. In conclusion, dietary supplementation with PHB, especially at the 1.00% level, enhanced growth performance and improved nutritional and health indicators in the fingerlings. These findings suggested that PHB had the potential to be a valuable dietary additive for this species.

Abstract This study was important to improve proper biosecurity measures and controlling the spread of Aeromonas to prevent future outbreaks. This research sought to determine whether virulent Aeromans species were present in morbid rainbow trout, their resistance and their genetic relatedness. A total number of 542 tissue lesion specimens were collected from gill, liver, heart and kidneys in morbid domesticated fish in Duhok province, Iraq. The gyrB DNA sequence analysis was used to determine the species classification. Drug susceptibility testing was conducted for all isolated strains using disc diffusion technique. The genotyping analysis was carried out using enterobacterial repetitive intergenic consensus-polymerase chain reaction. Thirty-four isolates were found and they were classified into three species (Aeromonas veronii, Aeromonas sorbia, and Aeromonas allosaccharophila), where A. veronii stand as one of the most prevalent species. The most frequently affected organ by Aeromonas was the gills among four different organs. The detection frequencies of the virulence genes aerolysin, outer membrane protein, glycerophospholipid-cholesterol acyltransferase, elastase, flagella, serine protease, cytotonic heat-labile, and hemolysin were 100%, 100%, 79.41%, 64.70%, 76.47%, 67.64%, 70.58%, and 41.17, respectively. None of the strains possessed all of the virulence markers. All isolates were completely resistant to ceftazidime, amoxicillin and doxycycline. All isolates were found to be multi-drug-resistant. Regardless of the nearest geographic source area of samples and the same Aeromonas species, there was a high genetic diversity. The results of this study could help farmers and researchers make informed decisions about measures of biosecurity and proper therapeutic drugs to apply to prevent current outbreaks and prevent them from recurring again.

Abstract Lecithotrophic larvae utilize extensive yolk reserves for early development. In this study, the effect of egg docosahexaenoic acid (DHA):eicosapentaenoic acid (EPA) ratios (i.e., 5.92, 10.08, 11.66, and 14.53) on the emerging larvae foregut development of rainbow trout was examined. Larvae samples were taken from day 22 to 36 post-fertilization. Thin whole body longitudinal sections were prepared and stained by Hematoxylin and Eosin and Alcian blue procedure. The sections were examined regarding epithelial layer thickness, intestinal fold height and mucosal layer thickness along with number of enterocytes and goblet cells. Results indicated that maximum thickness of the epithelium was observed on day 36 post fertilization in larvae hatched from eggs with DHA:EPA ratios of 14.53 and 10.08. The highest and lowest intestinal folds height were also observed in larvae hatched from eggs with DHA:EPA ratios of 10.08 and 14.53, respectively. The mucosal-submucosa layer thickness was the highest in larvae hatched from eggs with DHA:EPA ratio of 10.08. Enterocyte’s count was the highest in larvae obtained from eggs with DHA:EPA ratio of 10.08 on day 36 post-fertilization. The highest and lowest number of goblet cells were enumerated in larvae obtained from eggs with DHA:EPA ratios of 5.53 and 14.53, respectively. In conclusion, our results revealed that feeding rainbow trout broodstock with diet contained highly unsaturated fatty acids (HUFA):polyunsaturated fatty acids (PUFA) ratio of 0.28 could result in the egg with DHA:EPA ratio of 10.08 which in turn yielded larvae with better foregut development parameters compared to those larvae emerged from the eggs with increased DHA :EPA ratio.

Abstract A 35-day study investigated the impact of carbon sources and carbon/nitrogen (C/N) ratios on the microbial community of biofloc. For this purpose, we utilized a combination of phospho-lipid fatty acids (PLFAs) profiles and DNA-based sequencing methods to investigate changes in the microbial community composition and structure. The experiment involved three carbon sources including Dextrin (DEX), corn starch (CS) and wheat bran (WB) at two C/N ratios (19 and 30). The results indicated that WB and CS were found to decrease nitrogen metabolite concentration while increasing total suspended solids and bacterial density compared to DEX. The treatments exhibited variations in microbial communities and the use of polymerase chain reaction/ denaturing gradient gel electrophoresis analysis revealed distinct dominant bacterial species linked to carbon sources and C/N ratios. Furthermore, the highest levels of bacteria and protozoa PLFAs biomarkers were observed in the C/N30 ratio and WB treatment while the ratio for poly-β-hydroxybutyrate/PLFAs and fungi biomarkers displayed a decrease. Also, by incorporating the results of PLFAs profile and conducting a principal component analysis, the treatments were categorized into distinct groups based on both the carbon source and C/N ratios. Overall, both methods yield consistent results. PLFAs offered additional insights into the microbial composition beyond bacterial structure while DNA-based analysis provided finer taxonomic resolution.

Abstract The effects of resveratrol as an anti-oxidant in improving growth and health have been shown in several experiments. This study aimed to evaluate the effects of different dietary resveratrol inclusion levels on digestive enzymes activity and serum biochemistry of rainbow trout (Oncorhynchus mykiss). Accordingly, 225 juvenile rainbow trout with an average body weight of 10.00 ± 1.50 g were stocked in nine experimental units. The study was performed as a completely randomized design including three dietary levels of resveratrol as follows: 0.00, 400 and 800 mg kg^-1 feed. During the experiment, fish were fed based on their respective body weight using standard feeding tables at three feeding times for 8 weeks. Nine fish were randomly selected from each treatment at the end of the 4^th and 8^th weeks of the experiment. Results revealed that supplementing 800 mg kg^-1 feed resveratrol significantly increased lipase activity (31.40 ± 0.32 U mg^-1 protein) compared to the control group (29.92 ± 0.52 U mg^-1 protein) at the end of week eight. Also, at the same time, it increased serum high-density lipoprotein (123.04 ± 1.57 mg dL^-1) compared to the control group (97.055 ± 1.463 mg dL^-1). In addition, dietary supplementation of 800 mg kg^-1 feed resveratrol effectively reduced serum alanine aminotransferase, alkaline phosphatase and aspartate aminotransferase activities along with glucose, cortisol and cholesterol. In conclusion, resveratrol can be used as a suitable food supplement to improve fish health by increasing digestive enzymes activities.

Abstract This research explored the impacts of feed-born silver nanoparticles (AgNPs) on common carp (Cyprinus carpio) and whether dietary curcumin supplementation could ameliorate the impacts of AgNPs on growth, hemato-biochemical parameters and digestive enzyme activity. Nine experimental diets were prepared containing 0.00, 0.05, and 0.15 g kg^-1 AgNPs, as well as 0.00, 0.75, and 1.50 g kg^-1 curcumin in a factorial design. Triplicate groups of common carp (4.82 ± 0.41 g) were fed on the test diets for 60 days. The results demonstrated that AgNPs reduced growth performance and enhanced the feed conversion ratio dose-dependently. Supplementing 0.75 g kg^-1 curcumin at a low AgNP level improved the growth rate, while its inclusion at a high AgNP level led to further suppression of growth performance. The highest hematocrit value, hemoglobin concentration and white blood cell count were recorded in the group receiving 0.75 g kg^-1 curcumin. Serum glucose, cholesterol and triglyceride concentrations were elevated by increasing AgNP levels. However, curcumin inclusion, particularly at the lower level of AgNPs significantly decreased their values. Similarly, intestinal alkaline protease and lipase activities were progressively reduced by increasing dietary AgNP contents, but, significant improvements were observed by curcumin application at the lower AgNP level. Our results revealed that curcumin supplementation could limit the toxic effects of lower dietary AgNP contents.

Abstract The role of immunostimulants in reducing diseases and enhancing fish performance has been proven in various studies. In this study, the effects of antioxidant procyanidin and commercial probiotic Bio-Aqua^® on some hematological and immune indices of rainbow trout (Oncorhynchus mykiss) were investigated. A total number of 525 fingerlings in seven treatments (each treatment in triplicates) with experimental diets, including (1) commercial food without supplements (CTL), (2) 400 mg procyanidin kg^-1 feed (PC400) , (3) 800 mg procyanidin kg feed^-1 (PC800), (4) 0.50% probiotic diet (PB0.5), (5) 1.00% probiotic diet (PB1), (6) probiotic and procianidin 0.50% and 800 mg kg^-1 feed, respectively (PB0.5 + PC800) and (7) probiotic and procianidin 1.00% and 400 mg kg^-1 feed, respectively, (PB1 + PC400) were fed for eight weeks. The results showed that the use of procyanidin alone did not have any significant effect on blood biochemistry and immune indices. However, the individual use of Bio-Aqua^® probiotic could affect the hematological and immune indices of fish, except for monocyte, compared to the control and procyanidin treatments. However, the combined use of the supplements improved the hematological and immune indices of fish. It was concluded that the simultaneous dietary administration of procyanidin and probiotic Bio-Aqua^® could improve the general health of rainbow trout.

Abstract Arsenic (As) contamination in natural water resources has become a great disaster throughout the world posing serious health problems. The current study was performed to evaluate the protective effects of Escherichia coli strain Nissle 1917 (EcN) against As exposure in goldfish (Carassius auratus). Fish were fed three times a day with 4.00% of body weight of diet with different doses (0.00, 1.00 × 10⁶, 1.00 × 10⁷ and 1.00 × 10⁸ CFU g^-1) of EcN for 80 days and then, challenged with 20.00 mg L^-1 As for 96 hr under stagnant flow. Physicochemical characteristics of the inlet water were temperature of 25.10 ± 0.70 ˚C, pH of 7.30 ± 0.20 and dissolved oxygen of 7.30 ± 0.30 mg L^-1 and 50.00% of water was exchanged once a week. Afterwards, fish were euthanized with a clove oil solution (50.00 μL L^-1) and tissues were dissected from each fish and immediately fixed in 10.00% buffered formalin. The histopathological results indicated that the supplemented EcN did not have any side effects on various organs. It was also observed that the damages to kidney, liver, gill and skin were pronounced in fish exposed to As. However, the histopathological damages induced by As in fish tissues were less pronounced in the EcN-treated groups compared to the fish fed with the basal diet. Lamellar blood congestion in gills and epidermal cells detachment from the skin surface as well as hepatocytes, enterocytes and tubular necrosis were reduced in treated groups. These findings indicate that EcN has the potential to ameliorate the As-induced organ toxicity.

Abstract This study was undertaken to investigate the effects of feeding rainbow trout (Oncorhynchus mykiss) broodstocks with different ratio of plant oils to evaluate the changes in antioxidant defense status in the progenies. In the experimental diets, fish oil was replaced with different combination of plant oils including corn oil, olive oil, sunflower oil, and coconut oil, to gain different levels of polyunsaturated fatty acids (PUFA) and highly unsaturated fatty acids (HUFA) in the experimental diets. Fish fed eight weeks with experimental diets before reproduction. After spawning, samples were taken on days 0, 5, 10, 15, 20, 25, 30 and 35 after fertilization. The samples were homogenized, centrifuged and the supernatant was removed for determination of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) activity and malondialdehyde (MDA) content. Results showed that SOD activity was significantly increased from the first sampling to day 35 in all treatment groups. The CAT activity showed a downward trend, as the highest CAT activity was observed in the eggs immediately after fertilization. The GPX activity declined until day five and then showed an increasing trend. The MDA content did not show significant changes in different groups and at different sampling times. The antioxidant enzymes activity was significantly influenced by the dietary PUFA level in the experimental groups but no change in MDA content was recorded, suggesting that the different percentages of fish oil replacement used in this study could not result in oxidative stress in early life stages of O. mykiss.

Abstract Saprolegniosis is one of the most frequent diseases in the ornamental fish industry that may cause by Achlya spp. There is no report of fungal infection caused by Achlya spp. in Oscar (Astronotus ocellatus) in Iran. An Oscar fish was referred to the Veterinary Hospital, Shahid Chamran University of Ahvaz, Ahvaz, Iran with saprolegniosis symptoms including loss of appetite and yellow to gray cottony mass on the skinof flank and caudal peduncle. The infected area of the fish body was investigated by wet smear. After observing broad aseptate hyphae (approximate width 10-15 μm), the infected skin was inoculated on Sabouraud dextrose agar and incubated at 30 ˚C for seven days. The large fungi colony was appeared on the agar and the isolated fungi were detected as Achlya spp. after examination by wet and stained dry smears according to the morphology of hypha, spores, and zoosporangium. It is the first report of cutaneous saprolegniosis in Oscar caused by Achlya spp. in Iran.

Abstract The purpose of the present study was to isolate and identify the pathogenic agents in Acipenser stellatus (Pallas, 1771) and Huso huso, (Linnaeus, 1758) reared in the south of Fars province, Iran which have shown infectious disease signs. Samples from spleen and kidney of 32 fishes showing septicemia symptoms such as decreasing of appetite, unbalanced swimming, expanded wounds, and petechia on the body surfaces, pectoral fins rot, visceral hemorrhage, bleeding on the spleen, and heart ascites were collected. Then samples were cultured on brain heart infusion agar growth media, stain and biological and biochemical tests on purified bacteria were performed. On the other hand, 16S rDNA region of the isolated organism was amplified using PCR. The amplified gene fragment was sequenced and evolutionary history was inferred by phylogenetic tree construction using neighbor-joining method. Results indicated that two bacterial species including Chryseobacterium joostei which isolated from the kidney of stellate sturgeon (43.00%), and Aeromonas veronii which isolated from the spleen of both sturgeon species (75.00% and 31.00% from beluga and stellate sturgeon, respectively), were recognized. Phylogenetic tree analysis showed that Fars isolated organisms including A. veronii and C. joostei had highest similarity with A. veronii bv veronii and C. joostei isolated from France, respectively.

Abstract Monogenea is one of the most species-rich groups of parasitic flatworms worldwide with many species described from African freshwater fish. Little is known about the diversity and geographic distribution of monogenean parasites infesting the Red Sea fishes in Egypt. In the present study, a total of 45 specimens of the brushtooth lizardfish Saurida undosquamis (family: Synodontidae) and 35 specimens of the red porgy seabream Pagrus pagrus (family: Sparidae) was examined for monogenean infestation. Samples were collected from water locations at Hurghada coasts along the Red Sea in Egypt. Two different species were recovered. The first recorded parasite was Diclidophora merlangi infesting the lizardfish. This parasite was morphologically similar to the original description for the general body shape, size, shape and arrangement of the clamps and reproduction organs and the number of spines in the lateral groups of the genital atrium, but is distinguished in the host fish which is of a different genus. The second species was Loxuroides pricei. The morphological and quantitative data of the isolated specimens and the potential reproductive consequences supported their assignment to L. pricei than to the other congeneric species.This parasite can be separated from the morphologically similar L. sasikala through having a shorter distance from the anterior extremity to genital atrium or vaginal region, fewer testes and a slightly greater number of spines on cirrus and genital atrium. The two species represented new host and locality records from the Red Sea in Egypt.

Abstract The aim of this study was to evaluate pharmacokinetic profiles of florfenicol after a single dose of intravenous (5.00 mg kg^-1 body weight) and oral (40.00 mg kg^-1 body weight) administrations in common carp (Cyprinus carpio). The residue depletion of florfenicol was also investigated after oral administration (10.00 mg kg^-1 body weight) and bath treatment (5.00 mg L^-1) for 10 consecutive days. Pharmacokinetics of florfenicol in plasma after a single dose administration, at 10 time points (0.50, 1, 2, 4, 8, 12, 24, 72, 120 and 168 hr) and florfenicol concentrations in tissues (plasma, liver and muscle) at three time points (1, 7 and 14 days) after 10 consecutive days, were analyzed by high performance liquid chromatography. The peak concentration of florfenicol was 137.02 ng mL^-1 and the time to reach peak concentration in plasma was two hr. The elimination half-lives, the volume of distribution at steady state and total body clearance were estimated as 21.40 hr, 0.30 and 0.03 L hr^-1, respectively. After drug administration for 10 days, it's concentration in plasma and muscle in oral treatment was significantly more than bath treatment in all days. Drug concentrations in the liver after bath treatment were significantly higher for a shorter period than the concentration in the oral treatment, indicating that higher levels of florfenicol for a longer period can be achieved in the tissues after oral drug administration. According to pharmacokinetic results, florfenicol may be a suitable candidate for the treatment of common bacterial infections in common carp farming.
The aim of this study was to evaluate pharmacokinetic profiles of florfenicol after a single dose of intravenous (5.00 mg kg^-1 body weight) and oral (40.00 mg kg^-1 body weight) administrations in common carp (Cyprinus carpio). The residue depletion of florfenicol was also investigated after oral administration (10.00 mg kg^-1 body weight) and bath treatment (5.00 mg L^-1) for 10 consecutive days. Pharmacokinetics of florfenicol in plasma after a single dose administration, at 10 time points (0.50, 1, 2, 4, 8, 12, 24, 72, 120 and 168 hr) and florfenicol concentrations in tissues (plasma, liver and muscle) at three time points (1, 7 and 14 days) after 10 consecutive days, were analyzed by high performance liquid chromatography. The peak concentration of florfenicol was 137.02 ng mL^-1 and the time to reach peak concentration in plasma was two hr. The elimination half-lives, the volume of distribution at steady state and total body clearance were estimated as 21.40 hr, 0.30 and 0.03 L hr^-1, respectively. After drug administration for 10 days, it's concentration in plasma and muscle in oral treatment was significantly more than bath treatment in all days. Drug concentrations in the liver after bath treatment were significantly higher for a shorter period than the concentration in the oral treatment, indicating that higher levels of florfenicol for a longer period can be achieved in the tissues after oral drug administration. According to pharmacokinetic results, florfenicol may be a suitable candidate for the treatment of common bacterial infections in common carp farming.

Abstract This study evaluated preclinical and clinical safety of marshmallow (Althaea officinalis L.) extract as a naturopathic medicine in common carp deliberately infected with Aeromonas hydrophila. The fish were fed 0 (control), 2.50, 5.00 and 10.00 g of marshmallow extract for 60 days in a preclinical experiment and then, challenged with A. hydrophila for a 10-day experiment. Significant increases were observed in aspartate aminotransferase (AST), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), creatine phosphokinase (CPK) activities and plasma creatinine levels in fish fed 10 g marshmallow extract per kg feed. However, alanine aminotransferase (ALT) significantly decreased on day 60. The fish fed 2.50 g marshmallow extract per kg feed indicated increased levels of total protein and globulin. There were no significant changes in albumin levels (p > 0.05). 2.50 and 5.00 g marshmallow significantly decreased triglyceride and cholesterol levels and increased glucose levels (p < 0.05). A. hydrophila significantly increased AST, ALT, LDH, ALP and CPK activities and plasma glucose, cholesterol, triglycerides and creatinine levels after 10 days (p < 0.05). Total plasma protein, albumin and globulin levels in fish challenged with A. hydrophila were significantly lower than the control group (p < 0.05). Marshmallow extract at 5.00 and 10.00 g can adjust plasma biochemical parameters in fish challenged with A. hydrophila. The results of preclinical studies and pharmaceutical toxicity of marshmallow extract revealed that dietary levels lower than 5.00 g were safe and effective. The results of this clinical study demonstrated that marshmallow extract (5.00 g kg^-1 feed) can protect fish against A. hydrophila.

Abstract In this study the optimal amount of enriching Artemia franciscana with a synbiotic combination of Pediococcus acidilactici and fructooligosaccharide (FOS( was investigated. The experiment was conducted in a completely randomized design in ten treatments: multi-level probiotics P. acidilactici (1×10⁹, 1×10⁸ and 1× 10⁷ CFU per L) and multi-level enriched prebiotic FOS (1, 2 and 5) g per L of solution and control. To evaluate the enrichment of adult artemia with each treatment, sampling was performed at 2, 4 and 6 hr after initiation of enrichment. The results showed that a synbiotic containing a probiotic treatments P. acidilactici at 1 × 10⁹ and
1 × 10⁸ CFU per L had more bacteria than a synbiotic containing a probiotic treatment with 1 × 10⁷ CFU per L (p < 0.05), but did not show significant difference between levels of 1 × 10⁹ and 1 × 10⁸ CFU per L (p > 0.05). The highest number of attached bacteria (6.78 ± 0.03 log CFU g^-1) to adult artemia was shown after 6 hr of enrichment that showed significant difference with 2 hr, but did not show significant difference with 4 hr time. In conclusion, the results of this study showed that adult artemia in a short time (about 4 hr) unlike nauplii artemia can retain a large amount of probiotic (1 × 10⁸ CFU P. acidilactici per L and 5 g per L FOS prebiotic) on their own.

Abstract In this study the cranial nerves development of H. huso are explained from 1 to 54-days-old (1, 3, 6, 15, 21 and 54 days). Despite all the researches on fish brain, there are no study on nerves evolution on H. huso during their larvae life. For this research 40 samples of larvae H. husowere obtained (from each age, about six samples were selected). The specimens were maintained in fiberglass tank, then histological samples were taken from tissues and stained with hematoxylin and eosin for general histological studies using light microscope. According to the results, on 1 and 3-days-old, no nerve was observed. The terminal nerve and their dendrites were observed around the nasal cavity and the axons projected to different areas in forebrain especially around olfactory bulb diffusely, on 6-day-old fish. Also, olfactory, optic, oculomotor, trochlear, trigeminal, lateral line and vagus nerves were detected on 6-day-old fish, however two parts of lateral line nerve were separated on 54-day-old. Three nerves, profundus, facial and octaval were observed on 54-day-old, however, up to this age, epiphysial nerve was not observed.

Abstract The grass carp (Ctenopharyngodon idella) is a herbivorous, freshwater fish species of the family Cyprinidae, and the only species of the genus Ctenopharyngodon. Neoplasms in fishes are generally less aggressive than neoplasms in mammals and are most commonly discrete, focal and benign neoplasms. A 3-year-old grass carp with a big mass on the vertebrae was referred to the clinic. According to the owner’s statements, the fish had no signs of lethargy, ataxia and abnormal behaviors. The size of the mass was 7 × 6 × 6 cm. It cut hardly with audible sounds. The consistency of the mass was as hard as a cartilage. Microscopic examination revealed numerous irregular crests of hyaline cartilage beneath the skin. According to histopathologic characteristics, chondroma on the vertebrae of grass carp was diagnosed.

Abstract The present study was conducted to evaluate the status of the parasite fauna in Acipenser persicus at different development stages, in order to find prevention protocols for parasitic diseases in this valuable species. For this purpose, sampling from each sex breeder, 10 egg samples, 5-day-old larvae (n = 20), 20-day-old larvae (n = 80) and fingerling of A. persicus (n = 60) released in earthen ponds were done. After the bioassay and preparing wet mount from the internal and external organs, identification was done according to the keys. According to the results, no fauna parasites were isolated from egg samples and 5-day-old larvae; but Trichodina spp. was isolated from 20-day-old larvae. Also, the same protozoan was isolated from fingerling released in earthen ponds, the mean intensity, prevalence and range of contamination by fingerling were higher with compared to 20-day-old larvae. Trichodina sp. and Diplostomum spathaceum were isolated from skin and eyes of females, respectively. However, Trichodina sp. and Ichthyophthirius multifiliis were isolated from skin of male breeders. In this study, no parasites were isolated from internal organs of larves and fingerling but four intestinal parasites included: Cucullanus sphaerocephlaus, Anisakis sp., Skyrjabinopsilus semiarmatus, and Lepto-rhynchoides plagicephalu were isolated from internal organs of breeder. Based on a wide range of parasitic infection observed in various life stages of A. persicus, it seems necessary to consider hygienic and management measures.

Abstract The present study investigates the effects of different routes of inulin administration as prebiotic on gut microbiota and survival rate of Indian white shrimp post-larvae. Four hundred and fifty Indian white shrimp post-larvae (PL₁) were stocked in nine tanks. The tanks were assigned into three treatments: feeding with inulin-treated (110 mg L^-1) Artemia nauplii (I-T), feeding with inulin-enriched (110 mg L^-1) Artemia nauplii (I-E) and control which repeated triplicates. Feeding trial was performed until PL₁₁ stage and then gut microbiota was studied using culture based method. Also, survival rate was calculated at the end of feeding trial. Our results showed that feeding on inulin enriched or treated Artemia nauplii had no significant effect on total viable culturable autochthonous bacteria and Vibrio spp. levels of the gut microbiota (p > 0.05). However, a remarkable increase of lactic acid bacteria levels (LAB) was observed in I-E treatment (p < 0.05). Administration of inulin enriched Artemia nauplii significantly elevated survival rates of Indian white shrimp post-larvae (p < 0.05). These results encourage administration of prebiotic-enriched Artemia nauplii in post larval stage of Indian white shrimp but determination the mode of action of prebiotic on various aspects of shrimp larviculture merit further research.

Abstract The Karoun River is major source of water for warm‌water fish culture industry in southwest of Iran. The aim of the present study was to investigate the distribution of mercury in tissues of marketable common carp and in bottom sediments of fish farms in Khouzestan province. This study was carried out on 45 fish farms that are located on the bank of the Karoun River in Khouzestan province, south-west Iran. Concentration of mercury (Hg) was determined using spectrophotometery in three tissues (muscles, liver and gills) of farmed common carp (Cyprinus carpio), water and bottom sediments of fish farms collected from three regions (North, center and south) of the Karoun River, in Khouzestan province, Iran. The concentrations of Hg in muscle tissue (2.71 mg kg^-1 dry matter) of fish from the south were significantly higher (p < 0.05) than from the other two sites. In the center and south sampling zones, Hg concentration in muscle was found to be above the maximum tolerable values provided by Food and Drug Administration standards. The Hg concentration of fish farm sediment and water samples were ranged as 0.46 to 0.48 mg kg^-1 dry matter and 3.10 to 4.11 μg Hg L^-1, respectively. Finally, Hg concentrations at downstream site were higher than upstream site.

Abstract This study was conducted to determine the effects of mannan oligosaccharide (MOS) on growth, some immune responses and gut lactic acid bacteria of common carp. Four experimental diets containing 0%, 0.05%, 0.10% and 0.20% MOS were prepared. Each diet was randomly allocated to triplicate groups of fish with initial average weight of approximately 14 g. After eight weeks, survival rate was high in all treatments with no significant difference (p > 0.05). Growth performance including final weight, weight gain (WG) and specific growth rate (SGR) did not differ among the treatments. Feed conversion ratio (FCR) was better when the fish were fed 0.05 to 0.20% MOS diets. The alternative complement activity, lysozyme activity and serum total Ig were found to be significantly (p < 0.05) greater in fish fed 0.20% MOS diets. Although the total intestinal bacterial counts were not affected by dietary treatment (p > 0.05), the lactic acid bacteria levels were significantly elevated in fish fed MOS diets (p < 0.05). These results indicated that oral administration of MOS at 0.20% elevated the immune response, improved FCR and modulated intestinal microbiota of common carp.