The Health Status and Genetic Variations of the Bivalve, Pinctala radiata Affected by Environmental Pollution

Alexandria is the second largest city of Egypt and one includes a wide variety of industries which comprises 100 large factories and about 260 smaller ones. Untreated sewage and waste waters are discharged annually from large numbers of outlets into Alexandria coastal area through local sewage system. Marine mollusks such as oysters are exposed to multiple stressors [1]. Marine pollutants produce multiple consequences at the organism, population and ecosystem levels, affecting organ functions. Among such pollutants, carcinogenic compounds are of particular interest and tumors have indeed been detected in marine shellfish [2]. DNA alterations induced by chemical and physical agents include single and double strand breakages, DNA-DNA cross links, and DNA-protein cross links. Cholinesterases (ChEs) represent a well-known class of serine hydrolases. They are considered ubiquitous enzymes whose physiological function is to remove acetylcholine from synaptic clefts. AchE is thought to be mainly involved in neurotransmitter hydrolysis. ChEs have been found as polymorphic enzymes in invertebrates. Two forms of ChEs have been identified in Ostrea edulis and Mytilus spp. Recent transplant studies have demonstrated that peroxisome proliferation is a rapid (i.e. two days) and reversible response to pollution by PAHs and PCBs in mussels. When organisms are exposed to organic xenobiotics, an increase in volume and number of peroxisomes is also observed. These changes are often associated with an increase of enzyme activities involved in fatty acid oxidation, such as acetyle Co-A oxidase (Aox). Transports of xenobiotics have been found in aquatic invertebrates. The stress protein response was studied as an indicator of water quality in gills and striated muscle tissues of fathead minnows Pimephales promelas exposed to a wide range of concentrations of sodium arsenite for various time intervals. The stress protein response in gills was elicited rapidly, occurring by (2 hrs.) exposure at 25 mg/L. The response was tissue specific. In gills, synthesis and accumulation rates of 20, 40, 70, 72 and 74 KDa proteins were significantly increased compared to controls. In muscle, 20, 30, 68, 70, and 90 KDa proteins also showed significantly increased synthesis and accumulations. The use of molecular markers has become widely accepted as a valuable tool [3]. Williams et al. [4] were the first to describe RAPD markers; based on the amplification of random DNA segments with single primers of arbitrary nucleotide sequence. These polymorphisms, simply detected as DNA segments which are amplified from one sample but not the others and are visible as the presence or absence of particular RAPD bands, and are inherited in a Mendelian fashion and can be used to construct genetic maps in a variety of species [5]. Polymorphism results from mutation or re-arrangements at or between oligonucleotide primer binding sites in a genome. These polymorphisms are usually separated on agarose gels and visualized by ethidium bromide staining. Such polymorphisms behave as dominant genetic markers.