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Minerals ultility to aquaculture

      Minerals such as copper, manganese, iron, zinc, calcium, and magnesium play an important role in growth ,development, and maintenance of aquatic organisms. These minerals act as cofactors of many enzymatic sustems involved in metabolism (Frenet and Alliot 1985; Davis and Lawrence 1997) and in hormone and nucleic acid synthesis (Tolonen 1995). They also participate inosmo regulation and are components of tissues and structures; for example, calcium in the skeleton and copper in hemocyanin (Davis and Gatlin 1991). In general, the mineral supply depends on food and uptake from the water, although the net influx depends on the bioavailability of the minerals in the water.  Many studies have shown the importance of minerals in the diet of crustaceans during growth (for reviews see Davis and Lawrence 1997). Dietary deficiencies of elements such copper and manganese  can result in poor growth, high embryonic mortality and low hatching rate, whereas deficiencies of zinc can reduce the life span in penaeid prawns, such as the white shrimp, penaeus vannamei(Davis and Lawrence 1997)

      Reproduction in penaeid shrimp represents a critical step in shrimp culture, and broodstock nutrition plays and essential role in the optimal production of larvae. Although the requirements for some specific nutrients such as lipids have been emphasized, there are no reports on mineral dietary needs during penaeid reproduction(Harisson 1997). In commercial penaeid shrimp hatcheries, maturation is generally induced by eyestalk ablation, implying an increase in gonad development with a concomitant increase in nutrient mobilization to the gonads, a transfer that is not necessarily compensated by dietary intake (Harrison 1990). This potential deficit is critical with successive spawnings of each female during the production cycle of a hatchery. A deterioration of spawning quality under these conditions has been reported as reproductive exhaustion caused by an energy deficiency (Primavera 1985;Palacios et al.1990). other specific minerals such as copper, zinc, iron.and manganese, however,seem to be depleted as a result of continual intensive reproduction in Penaeus vannamei (Mendez et al.1998). The importance of minerals in crustacean reproduction is not clear, although it is recognized that during reproduction there is a change in mineral distribution in gonadal tissues(Paez-Osuna and Ruiz-Fernandez 1995; Jeckel et al.1996). A sex-specific pattern of metal distribution related to gonadic development has been observed during reproduction in tissues of the red shrimp Pleoticus muelleri (Jeckel et al.1996). in males, increased mineral concentration in that occur during the reproductive process in the case of penaeid shrimp.

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