Parasites Monitoring Schemes
Catching fish
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After identifying the fish which contains the parasite of interest, the most
effective way to study the parasite is to catch the fish. After catching
the desired fish and extracting the parasite, the next step is compare the
concentration of specific toxins within the tissues of the host and the parasite.
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Parasite Data
Parasites are potential
indicators of environmental quality due to the variety of ways in which they
respond to anthropogenic pollution. They provide valuable information about
the chemical state of their environment not only through their presence or
absence but also through their ability to concentrate environmental toxins
within their tissues.
Knowledge of fish
parasites is of particular interest in relation not only to fish health but
also to understand ecological problems. This interest especially in fish
parasites is related with the high number of parasites species commonly found
in or on freshwater and marine fish. Parasites are useful in two different
ways.
First of all, they
are "effect indicators" (effects of various forms of pollution on the abundance
and distribution of parasites). We can monitor the changes of the whole population
structure depending on the pollution of the environment. However, there
are also problems using parasites as effect indicators. This is because there
is a wide variety of factors affect the population of parasites. Thus, although
studies on diversity of fish parasites in different biotopes are important
and extremely interesing, they do not allow any conclusions to be drawn concerning
the concentration of specific toxins in the environment.
- ex. Monogenean
Trematode are parasites which live on the gills of fish. Therefore, they
are in direct contact with both the surrounding environment and the fish
host. In addition, it has a short life, thus react immediately on changes
in environmental factos.
- ex.. Zebra mussels
Dreissena and Rainbow trout Salmo gairdneri are indicators
for water treatment in sewage plants.
- ex. Effluent from
a pulp and paper mill result in abundances within communities of Dactyloyrus
and Paradiplozoon.
Second, they are "accumulation
indicators" (acculmulation of toxins within parasites). We can monitor the
environment by looking at the concentration of environmental toxins within
the parasites. These parasites usually have higher amounts of metals than
the host tissues main uptake and accumulation of metals occur in adult worms
inside the gut of the host.
- ie. Acanthocephalans
a group of intestinal worms commonly found in fish. Adult worms live inside
the intestine of the final host and absorb their nutrients across their tegument
(no mouth/intestine). There are three major species: Pomphorhyndchus laevis,
Acanthocephalus lucii, Paratenuisentis ambiguous. Among these, P. Laevis
most rapidly reacts to changes in the environment. (ie. The mean concentrations
of lead and cadmium in P. Laevis are respectively 2700, 400 times higher
than in the muscle of the host and 11000, 27000 times higher than in water.)
Acanthocephalans can accumulate toxic metals from the aquatic environment
to concentrations even surpassing those in Dreissena polymorpha (=Mussel:
one of the best established accumulation indicators in fresh and brackish
waters in Eruope and USA).
- ie. The lead burdens
in the parasites is about 1000 times higher concentrations than that of host's
muscle. This is because metal concentration in the parasite is likely to
respond rapidly to changes in environmental exposure. The presence of acanthocephalans
had a significant impact on lead accumulation in the intestinal wall. The
fish infected with acanthocephalans only half of uninfected chub's lead concentration.
Sources
The use of fish
parasites as bioindicators of heavy metals in aquatic ecosystems
Authors: Sures, Bernd
Source: Aquatic Ecology 35: 245-255
Date: 2001