The application of nanoparticles in various industries has grown significantly in recent years. The aims of this study were evaluation effects of silver nanoparticles (AgNPs) on survival rate and tissues (Gills) of Guppy (Poecilia reticulate) as a model of the freshwater organism. For this purpose, 90 mature fish were exposed to a different level of AgNPs for 96 hr. Data analyzed showed there was a significant correlation between fish mortality rate and AgNPs concentrations. Histological assays showed some typical tissue damages such as hyperplasia, hypertrophy, hyperemia, hemorrhage, and necrosis. Moreover, fish exposed to a lethal concentration of AgNPs showed some clinical signs, such as increasing operculum movement, swimming near the water surface, anxiety, and death with open mouth. The results of the present study showed that AgNPs can have toxicity effects on Guppy, also to sub-lethal concentrations, leading to several tissue damages and reduced survival rate of fish.
The type of oil and how the physical and chemical properties of oil and its derivatives determine the dangerous degree of oil leaked in water. Hydrocarbons (H-c), which make up 95% of petroleum compounds, are considered toxic
Anthropogenic sound is currently recognized as a source of environmental pollution in terrestrial and aquatic habitats. Elevated sound levels may cause a broad range of impacts on aquatic organisms among taxa. Sound is an important sensory stimulus for aquatic organisms and it may cause fluctuations in stress-related physiological indices and in a broader extent induce behavioural effects such as driving as a distracting stimulus, masking important relevant acoustic signals and cues in a range of marine and freshwater species. However, sound exposure may also induce changes in swimming activities, feed efficiency and productivity of available food sources in fish. Here, we experimentally tested sound effects on swimming activities and foraging performance in thirty adult Zebrafish (Danio rerio) individually in captivity. We used adult zebrafish and water flea (Daphnia magna) as model predator prey, respectively. We also used four sound treatments with different temporal patterns (all in the same frequency range and moderate exposure level). Our results constitute strong evidence for clear sound-related effects on zebrafish behaviour. All sound treatments induced a significant increase in the number of startle response, brief and prolonged swimming speed for zebrafish (P<0.05). Zebrafish reached to the baseline swimming speed after 60 seconds in all treatments. We found partially brief and prolonged sound effects on spatial distribution of zebrafish; Although we did not find any significant sound-related behavioural changes for horizontal spatial displacement in all treatments (P>0.05), zebrafish swam significantly more in the lower layer of the fish tank except irregular intermittent 1:1-7 in brief sound exposure (P<0.05). The results of foraging performance showed that food discrimination error was low for the zebrafish and unaffected by sound treatments (P>0.05). However, food handling error was affected by sound treatments; all treatments caused a rise in handling error (P<0.001). This study highlights the impact of sound on zebrafish swimming activities, and that more attacks are needed to consume the same number of prey items under noisy conditions.
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