Studies on the defence and stress related factors of Oyster and Mussels of mariculture importance

Paulton, M P (2012) Studies on the defence and stress related factors of Oyster and Mussels of mariculture importance. Doctoral thesis, Mangalore University, Mangalore.

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    Marine bivalves are regularly exposed to biotic and abiotic stressors throughout the life in their natural habitat. The molecular mechanism with which the intertidal oysters and mussels manage such situations are mediated through defence and stress related proteins such as heat shock proteins and antioxidant enzymes. The present study was aimed at , molecular identification, characterization and expression analysis of the genes of selected heat shock proteins and antioxidant enzymes in the Indian edible oyster Crassostrea madrasensis and tropical brown mussel Perna indica. Molecular identification and complete characterization of the heat shock protein70 (HSP70) gene and the antioxidant enzyme superoxide dismutase (Cu/Zn SOD) gene of both the species were successfully carried out. Amino acid sequences were deduced from the full length coding sequences and used for the identification of the characteristic domains, homology search, and phylogenetic analysis etc.. The study was also extended to the partial characterization of the gene coding for heat shock protein90 (HSP90) as well as other antioxidant enzymes such as glutathione peroxidase (GPX) and catalase (CAT), and an important peptidase gene Leucine aminopeptidase (LAP) with vital role in protein turnover and salinity tolerance. The sequences were deposited in NCBI GenBank. The temperature tolerance limits such as sub lethal temperature (SLT) and lethal temperature (LT) in both the species were determined as a pre-mediated step for the study of gene expression induced by exposure to sub lethal thermal shock. The SLT and LT limits of the candidate species living in the tropical waters were revealed to be higher than their counterparts in temperate waters. The Indian edible oyster was found to be the most thermo tolerant among the various oyster species. A semi quantitative PCR approach was adopted to study the relative gene expressions in animals exposed to sub lethal temperature as well as in control animals. The genes like HSP70 and SOD were found to be up regulated on exposure to sub lethal temperature. The other genes studied were also found to be up regulated in general with slight variations in the expressions. All the gene expressions were found to be statistically significant (P<0.05). Gene expressions in oyster and mussel living in their natural habitat were found to show up regulations and down regulations consequent to stressful situations during different seasons. Keeping in view of the up regulation of the genes, the study was further extended to observe induced thermal tolerance in them as the same phenomenon was reported in Pacific oysters. For this, the oysters and mussels recovering from SLT shock were again exposed to lethal temperatures (LT ) at regular intervals, and their survival was monitored. The oysters were found to be surviving the LT up to twenty six days post SLT and this is the longest duration of induced tolerance ever reported in any animal. The mussels were found to tolerate LT up to one week post SLT. Thus the phenomenon of induced tolerance was established in the oyster and musses living in the tropical climate. The relative expressions of the different defence and stress related genes worked out during this study can be effectively used as biomarkers for monitoring environmental pollution and to assess the health status of aquatic animals in mariculture. The induced tolerance observed in this study can be effectively used to select healthy and sturdy brood stock for selective breeding and thus develop oysters with better environmental adaptability.

    Item Type: Thesis (Doctoral)
    Uncontrolled Keywords: stress; oyster; mussels; mariculture; bivalve species; Crassostrea madrasensis; brackish water oyster; physiology
    Subjects: Fish and Fisheries > Fish physiology
    Molluscan Fisheries > Bivalves
    Divisions: CMFRI-Kochi > Physiology and Nutrition Pathology
    Subject Area > CMFRI > CMFRI-Kochi > Physiology and Nutrition Pathology
    CMFRI-Kochi > Physiology and Nutrition Pathology
    Subject Area > CMFRI-Kochi > Physiology and Nutrition Pathology
    Depositing User: Dr. V Mohan
    Date Deposited: 25 Mar 2014 04:44
    Last Modified: 29 Nov 2016 07:27

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