Scientific Annals of the Danube Delta Institute (Sep 2011)
Short-term exposure of sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) fry to high concentrations of the pesticide Dimilin® (diflubenzuron); effects on survival and histology
Abstract
In the present study, the effects of Dimilin® on the survival and histology of two commercially important marine fish species, sea bream and sea bass, after a short-term exposure, were examined. Sea bream and sea bass fry of similar mean weight (0.25±0.05g SD) were exposed to three concentrations of the pesticide (diflubenzuron), 1500, 1000 and 500 ppm, for 96 h. For each species, three groups of ten fish (replicates) were exposed to each concentration,while three groups were not exposed and kept as controls. The mortality was recorded daily and tissue samples from fish of allgroups were collected for histological examination, after 24 and 96 h exposure. During the first 24 h of exposure, almost all seabream exposed to 1500 and 1000 ppm died. Similarly, almost all sea bass fry exposed to 1500 ppm also died but few fishexposed to 1000 ppm survived. Throughout the exposure period, sea bream fry exposed to 500 ppm exhibited similar survivalwith this of the control groups (percentage of alive fish after 96 h: 73.3±25.1% SD and 70±17.3% SD respectively), while seabass fry exposed to the same concentration exhibited significantly lower survival rate compared to that of the control groups(percentage of alive fish after 96 h: 26.6±20.8% SD and 86.6±5.7% SD respectively). The histological examination indicatedsimilar findings for both species. As the fish exposed to 1500 and 1000 ppm died in the first 24 h of exposure, before collectingthe tissue samples, the gills exhibited severe lesions of autolysis.The tissue samples of the fish exposed to 500 ppm werecollected from live fish and these revealed severe extensive hyperplasia and hypertrophy of the gill respiratory epithelium.These lesions became more pronounced after 96 h exposure. Only areas of mild hyperplasia / hypertrophy of the respiratory epithelium were observed in fish from the control groups, after 24 and 96 h exposure. No lesions in the internal organs of the fish exposed to Dimilin® were observed neither after 24 nor after 96 h exposure.
