جستجوی مقالات مرتبط با کلیدواژه « Cyanobacteria » در نشریات گروه « شیلات »

Cyanobacteria, ancient photosynthetic prokaryotes, form harmful blooms that degrade water quality and pose many risks to human health. The main objective of this study is to identify toxic cyanobacteria present in fish ponds, evaluate their effects on Zebrafish (Danio rerio) tissue, and investigate their characteristics. Samples were collected from the walls and floors of rainbow trout raceway ponds at Alborz Caspian Company, situated in Alborz province, Iran. The purpose of this collection was to isolate and examine cyanobacteria colonies. As a result of meticulous microscopic and macroscopic observations, three pure samples of Calothrix sp., Nostoc sp., and Microcystis sp. species were successfully identified. These samples were then transported to the laboratory and processed using the Z8 solid culture medium within a growth chamber. Cyanobacteria were identified based on their morphology using a light microscope and validated identification keys. The DNA extraction was performed using the cetyl-trimethyl-ammonium bromide method. Zebrafish were acclimated and fed with fish food containing lyophilized cyanobacteria for a period of 30 days. At specific intervals, fish were collected for histopathological analysis and measurement of antioxidant enzyme activity. The histopathological examination of intestinal tissue in the treatment groups exposed to lyophilized cyanobacteria revealed lesions including hyperplasia of enterocytes, reduction in their length, vacuolation of enterocytes, hyperplasia of goblet cells, and infiltration of lymphocytes. The gill samples from the treatment group exhibited severe histopathological abnormalities such as displacement of epithelial cells, fusion of lamellae, epithelial necrosis, and lymphocyte infiltration. These symptoms diminished over time. Hepatocellular lipid changes and vacuolation were observed in the treatment group's liver samples, peaking on the 30th day. The activity of superoxide dismutase (SOD) enzyme significantly increased in the exposed Zebrafish on the 30th day compared to the control group, and similar significant increases were observed on the 20th and 30th days (p<0.05). There were no significant differences in Catalase (CAT) activity between the control and treatment groups (p>0.05). Generally, the study identified specific histopathological abnormalities in the fish exposed to lyophilized cyanobacteria and observed changes in antioxidant enzymes activity. These findings contribute to understanding the impact of cyanobacteria on fish health status.

The cyanobacterial bloom leads to the deterioration of the aquatic environment because they release their secondary metabolic to the water, especially toxins. One of the important toxins is Cylindrospermopsin (CYN) which is one of the dangerous toxins that cause liver damage known as hepatic toxin, which poses great health risks to humans. Light plays an important role in the production of these toxins by cyanobacteria through its effect on the photosynthesis processand the gene regulator of these toxins. The current study tested the effect of different light intensities of 26, 52, 78, and 104 mol m-2s-1on hepatotoxic CYN production by cyanobacterium Nostoc ellipsosporum. The findings of this study showed that the highest inter and extracellular CYN reached 0.047 and 42.5 μg/ml, respectively with a total value of 42.547 μg/ml recorded at the light intensity of 78 μmol photons m-2s-1. The lowest production of intra and extracellular CYN was recorded at the light intensity of 26 μmol photons m-2s-1, which amounted to 0.0006 μg/mg and 7.73 μg/ml, respectively with a total value of 7.735 μg/ml. Also, the highest light intensity inhibited the CYN production which recorded 0.009 μg/mg and 26.39 μg/ml for intra and extracellular contents, respectively, and total production of 26.399 μg/ml. We conclude that light intensity has a vital role in CYN production especially in the optimal condition represented by moderate light, and this effect differs among different cyanobacterial species.

Alkaline pH is one of the most important problems of our aquatic habitat. We used Stigonematalean native cyanobacterium Fischerella sp. FS 18 as our model strain, andstudied it under different alkaline pHs (7, 9 and rarely 11) under two different – short and long- time treatments (24 and 96 hours after inoculation). Spectroscopic results showed that both alkalinity and time affected growth rate, phycobilisome and chlorophyll production. Response surface plot analysis of distribution showed that the pH borders between 8.5 to  9 would be critical at 24 hours after inoculation reaching to the highest rates of phycobilisomes. Spectrofluorimetric analysis showed that the highest photosystem I/ photosystem II may be seen at 24 hours at pH9. Photosynthesis- Irradiance curves showed that the highest rate of maximum photosynthesis belonged to pH9 in the short time treatment (24 hours). Increasing the time (96 hours) decreased the maximum amount of oxygen liberation significantly. Moving from the optimum conditions (even slightly) caused a sharp decline in the amount of alpha. The slope of decline was steep until near neutral and longtime condition.  Decreasing the time, and at the same time increasing alkalinity (alkaline pH) caused higher activity of photosystems especially photosystem I which lead to higher reductant production and cyclic electron flow operation. Distinct borders of pH (8.5-9) at 24 hours caused considerably high growth and matter production. This was naturally true for phycocyanin, phycoerythrin and the other economically important matters.