Research on Interrelationship between some Species of Freshwater Fish and Helmintic Larvae within Aquatic Ecosystems Polluted with Heavy Metals

Abstract

The objective of this study was to investigate the ability of some larvae of cestodes and nematodes which live in freshwater fish (intermediate hosts), to exhibit an uptake of heavy metals. According to some scientifical papers treating this subject, only adult worms were able to absorb successfully heavy metals within their hosts. Furthermore, it is believed that only the adults would act as biofilters and consequently as trustworthy indicators of environmental pollution. This study, carried out on the Danube Delta area, comes to prove the ability of the larvae to absorb heavy metals within their hosts, even when the pollution level with respect to heavy metals is very low. Following the biochemical analyses of water, sediment, aquatic plants, larvae and fish tissues (liver and muscle) samples, it resulted that the larvae were able to absorb important quantities within their hosts, so that only scarce amounts to be found in the muscle and liver. Both parasites were able to accumulate some heavy metals within their hosts, although only one of them did it successfully.

Keywords

• parasitic larvae
• fish
• biofilter for aquatic pollution
• heavy metals