Genetic variability in esterases and the insecticide resistance in brazilian strains of Oryzaephilus mercator and Oryzaephilus surinamensis (Coleoptera: Silvanidae)

Oryzaephilus mercator and O. surinamensis are stored grains and processed food pests, the latter being responsible for major economical losses. Polyacrylamide gel electrophoresis was used to analyse esterase patterns during insect development. Seven esterases, three cholinesterases, two carboxylesterases and two acetylesterases, were identified in O. mercator, one of which was proper to adults. Five esterases, of which four were cholinesterases, occurred in O. surinamensis. Strains of O. mercator and O. surinamensis were also exposed to malathion and chlorpyrifos-methyl. According to the LC50 estimates, OmLC-M and OmLA strains of O. mercator and OsLB strain of O. surinamensis were the most resistant to both insecticides. However, higher sensitivity to malathion and chlorpyrifos-methyl has also been verified in some of its esterases. Cholinesterases OmEST-1 and OsEST-5 seem to be involved in this resistance. These results suggest that organophosphate tolerance may be related to genetic variability in esterase isoenzymes.

Effect of copper on soluble proteins and enzymes in freshwater mussel Dreissena polymorpha

Dreissena polymorpha mussel were collected from Al-Kadesia lake - Haditha /Al- Anbar Governorate-Iraq. The animals were exposed to 1, 2 and 4 mg copper/l of water for eight days. The soft tissue was analyzed for the effect of copper on total protein components and activity of six enzymes (using colorimetric and /or electrophoretic methods). Copper was found to cause (a) Change in the intensity of some esterase patterns and increase of total protein by increasing the exposure time to copper (b) Increase in the activity of the enzymes, Aspartate amino transaminase (AST) and Alanine amino transaminase (ALT), and decrease in the activity of alkaline phosphatase (ALP) and acid phosphatase (ACP) . (c) Lactate dehydrogenase (LDH ) activity was decreased after exposure to the metal. These changes may be useful as an early indicator for water pollution with copper .