Biomedical Engineering Reference
In-Depth Information
DHA), and arachidonic acid (20:4 n -6; AA), all of which are of pivotal importance for
the production of high-quality gametes and offspring (Watanabe, 1982), and have
been specifically shown to enhance reproduction in zebrafish (Jaya-Ram et al., 2008).
Certain vitamins, including retinoids and ascorbic acid in particular, are also known to
be extremely important for long-term reproductive quality and health, and should be
considered in diet selection (Dabrowski and Ciereszgo, 2001; Alsop et al., 2008).
The type of feed is also of critical importance. Zebrafish may be fed live prey
items, processed diets, or some mixture of the two. Since the specific nutritional
requirements of zebrafish have yet to be determined, and may be fundamentally
different from even closely related species, it may be unwise to feed an exclusively
processed diet, especially since systematic studies of adult zebrafish performance on
these diets are not available. Live prey items such as Artemia typically possess
relatively balanced nutritional profiles (Watanabe, 1982) and therefore aremost likely
to meet much of the requirements of zebrafish. Processed diets may be included to
the diet as a supplement to Artemia , as they can be used to deliver specific nutrients
that may not be present in sufficient levels in Artemia or other live prey items. For
example, Artemia are deficient in DHA and in stabilized vitamin C (Lavens and
Sorgeloos, 1996). One way to address these inadequacies is to incorporate a prepared
feed containing known levels of these nutrients into the diet to help ensure that these
dietary requirements are adequately met and reproductive function is supported.
Finally, it is essential that feeds be stored and administered properly. This is
particularly critical for processed feeds. The typical maximal shelf life of a processed
feed does not exceed 3 months, when maintained in cool, dry conditions (Craig and
Helfrich, 2002). Oxidation of feed components, particularly fatty acids, increases
with temperature. Thus, feeds should be kept in airtight containers, refrigerated, and
discarded after 3 months to ensure that fish stocks derive maximal nutritional benefit
from their application. In terms of delivery, processed feeds should be fed dry to
minimize leaching of water-soluble amino acids and vitamins upon administration
(Pannevis and Earle, 1994; Kva
le et al., 2007).
1.4.3 Genetic Management
Small, closed populations of laboratory strains of animals such as zebrafish are subject
to a continuous loss of genetic diversity stemming from founder effects, genetic drift,
and population bottlenecking (Stohler et al., 2004). This loss of genetic diversity can
cause a number of problems relative to reproductive potential of zebrafish breeding
stocks. Continued breeding between close relatives will lead to accumulation of
deleterious alleles in breeding populations. These alleles may directly affect a number
of factors related to reproduction, including reduced quantity and quality of embryos.
Reduced genetic diversity may also manifest itself in reduced spawning rates, as
zebrafish show preference to associate with nonrelatives over siblings or closely
related individuals (Gerlach and Lysiak, 2006). Thismode of kin recognition, which is
thought to help avoid inbreeding in natural populations, may result in decreased
spawning rates when fish in a breeding population are closely related.
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