               !    "   # $ !  % " !  & ’(’ ! )% *+  375  ! "   +  ( ,-./ 01(203                       !"!     JOYCELYN C. JUMAWAN 1,2* , THUCYDIDES P. SALUNGA 2 and ELENA S. CATAP 2 1 Natural Sciences Department, CARAGA State University, Butuan City, 2 Institute of Biology, College of Science, University of the Philippines, Diliman 1101 Quezon City, the Philippines. *Corresponding Author: Phone (632) 9818500 loc 3727,3726; Fax:(632)=920=5471,Email: joycejumawan@gmail.com Received: 9 th September 2010; Revised: 13 th October 2010; Accepted: 18 th October 2010 #$$% Lipid peroxidation and patterns of cadmium and lead accumulation in the gills, liver, gut and muscles of  Gill, 1858 from four stations in Marikina River, Philippines were analyzed to study effects of possible metal toxicity alongside stress response. Mean cadmium (Cd) concentrations from tissues studied are within permissible amounts (0.02=0.05 mg L =1 ); mean lead (Pb) concentrations from the muscles, gills and gut were within permissible amounts except for the liver (0.22 mg L =1 ). Lipid peroxidation, indicative of oxidative stress was highest in the spleen, followed by the liver and gills. Malondialdehyde (MDA) values were not correlated with lead and cadmium concentrations in fish samples and were not site= significant which suggest that other possible factors might have also contributed to oxidative stress aside from lead and cadmium determined in the study. Histological observations of gills and gut show fair health for this invasive catfish, confirming several adjustments and adaptations towards air=breathing, although minute pathologic observations were seen in the liver. This study is the first to assess the patterns of heavy metal accumulation in this pollution=tolerant fish under field conditions in relation to oxidative stress. & ’()% Bioaccumulation, Janitor fish, oxidative stress,   The suckermouth sailfin catfish  Gill,1858 is distributed naturally in the Amazon River basin which runs through Brazil and Peru [44] but has successfully invaded and ISSN 0126=2807 Volume 5, Number 4: 375=390, October=December, 2010 © T2010 Department of Environmental Engineering Sepuluh Nopember Institute of Technology, Surabaya & Indonesian Society of Sanitary and Environmental Engineers, Jakarta Open Access http://www.trisanita.org This work is licensed under the Creative Commons Attribution 3.0 Unported License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.