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Abstract(s)
Aquaculture production is an important food source for human consumption worldwide, benefiting from methodologies that enable the development of advantageous phenotypic traits and, consequently, the reduction of biological and economic losses. Organisms exposed to environmental stimuli at early life stages can undergo molecular responses associated to increased tolerance to abiotic and biotic stressors. Rotifer Brachionus sp. has been crucial for the development of sustainable aquaculture practices, since it is used as first live food for several species’ larvae, allowing a stable production of aquatic seedling. Moreover, it has been used as model organism in several research fields, due to characteristics such as short life cycle and ease of handling. For these reasons, two strains of B. koreanus were used in this thesis to understand the potential of heat stress in early stages of development to induce tolerance to several environmental stressors later in life, and to study possible molecular mechanisms involved in this phenotypic alteration. Although genetically and morphologically identical, MRS10 and IBA3 strains showed differences in several life parameters and in tolerance to various stressors. Overall, the non-lethal heat shock (NLHS) conditions determined in this thesis proved to successfully induce tolerance to heat stress, high salinity, hydrogen peroxide, and cadmium chloride in rotifers. Induced thermotolerance was concomitant with up-regulation of several hsp genes and increased production of HSP70, whilst epigenetic alterations showed to have a major role in the development of cross-tolerance mediated by NLHS, with up-regulation of genes related to histone H3 modifications, and increased levels of total acetylation of histone H3. This thesis demonstrated the potential of Brachionus sp. as model organism to study molecular mechanisms underlying induced tolerance, and of NLHS as promising method to improve culture conditions of rotifers, with clear advantages for the aquaculture sector.
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Keywords
Aquaculture Cross-tolerance Epigenetic mechanisms Heat shock proteins Non-lethal heat shock