THESIS APPROVAL
THESIS APPROVAL
THESIS APPROVAL
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(1988) who investigated subacute responses of L. hoffmeisteri exposed to endrin in<br />
sediment. Likewise, Lotufo and Fleeger (1996) demonstrated that sedimentscontaminated<br />
pyrene and phenanthrene caused reduction of egestion rate and<br />
reproduction of L. hoffmeisteri. As a result of this study, however, neither worm<br />
biomass nor feeding rate has been assessed. For further investigations it should be to<br />
attend in these terms as mentioned above to the better explanation of a reduction in<br />
reworking activity which affects the population dynamics of L. hoffmeisteri.<br />
In the present study, lethal as well as sublethal effects demonstrated a<br />
dose-response relationship. It was found that the EC50 values of autotomy for<br />
L. hoffmeisteri are nearly about 2 times lower than the LC50 values, while the EC50<br />
values of sediment avoidance are similar to the LC50 values. This level of response<br />
suggests that naphthalene have more potential to change morphological feature than<br />
directly killing individuals. In contrast, from that level, it could be said that<br />
evaluation of burrowing behavioral alteration is as good as assessing on mortality.<br />
The observation also implies that loss of the posterior end of the worms may be more<br />
sensitive indicator of environmental impact of chemical pollutants.<br />
There are many other factors that may have some influences on the toxic<br />
effects of naphthalene in this study such as experimental procedures, chemical and<br />
physical characteristics conditions (Reynoldson et al., 1996). Another factor which<br />
may affect the toxicity of naphthalene is different constituent corporating in the<br />
species of organisms used. For instance, Sager and Pucsko (1991) found that<br />
different feeding behavior of animals could be an important factor which may have<br />
affected the toxic stress. Reynoldson et al. (1996) suggested that genetic variability<br />
of organisms may cause differences in the responses to toxicant. Moreover, Klerks<br />
and Bartholomew (1991) stated that distinct physiological mechanisms of<br />
oligochaetes seem to have a key function with respect to the availability of toxicants<br />
within the organisms. From these documented data, it is recommended that more<br />
laboratory works are necessary to examine the interaction between these variability<br />
and the animal bioassay. The benefit of the anticipated data could be available for<br />
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