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.