THESIS APPROVAL

transferred through the diet. Rotifers Brachionis plicatilis bioaccumulated
naphthalene and phenanthrene in their tissues after fed algae Isochrysis galbana
cultured in such contaminants -dosed water (Wolfe et al., 1996, 1998, 1999).
Similarly, Wolfe et al. (2001) reported that naphthalene was uptaken by larva
topsmelt Atherinops affinis via trophic transfer by eating this rotifer population during
the exposure. Likewise, clams Mercenaria mercenaria fed diatoms Thalassiosira
pseudomana cultured in benzo (a) pyrene-spiked water bioaccumulated that PAH in
their tissues (Dobroski and Epifano, 1980). Based on these evidences, it was
concluded that the difference observed in tissue PAH distributions between the two
species could result from different trophic levels, different diet, and also different
bioavailability of the compound as well (Baumard et al., 1998).
108
Biotransformation capacities of fish had shown a greater impact on
bioaccumulation and biomagnification of PAHs via a trophic transfer (Baumard et al.,
1998). As a detoxification mechanism, MFO enzymes, with the cytochrome P450
monooxygenase system, play a major role in the metabolism and activation of PAHs
to convert lipophilic contaminants into water soluble forms, which can then be more
readily excreted (Lee et al., 1972b; Djomo et al., 1996). Several studies reported that
many species of fish have a MFO enzyme, such as mosquito fish Gambusia affinis
(Chamber, 1979), killi fish Fundulus heteroclitus (Stegeman, 1979) and rainbow trout
Salmo gairdneri (Stegeman and Chevion, 1980), which parent compounds are broken
down to metabolite that are ultimately excreted in the bile (Howard, 1989; Varanasi
et al., 1989; Hellou et al., 1999; Klumpp et al., 2002). Opposite with invertebrates,
biotransformation of PAHs naturally occurs at slower rate due to lower concentration
of cytochrome P450 (Jame, 1989; D’Adamo et al., 1997; James and Boyle, 1998; Lee,
1998). According to these evidences, it could be exhibited from this study that the
gradual decrease of naphthalene in the muscle tissue during the exposure may be the
result of induced biotransformation enzymes, and subsequent elimination via the bile
of the Tilapia. This is also agreed with the work of Anderson (1979), James (1989),
Burkhard et al. (1994) and D’Adamo et al. (1997). In addition, it may be indicated
higher residue of naphthalene bioaccumulated by those invertebrates stated before