Biomedical Engineering Reference
In-Depth Information
Little else has been published in this area, although a study of the effects of
varying the size of the breeding insert itself on spawning success and egg production
showed no difference in spawning success between control cage of 3.5 L and test
cages of 500, 400, 300, 200, and 100 mL, and reduced production in 200 and 100 mL
sizes (Goolish et al., 1998). However, since this particular study was conducted in
recirculatingwater (test chambers were placed inside large on-system tanks), it does
not present a clear picture of the effect of chamber size on breeding efficiency in
static tanks.
There are a number of strengths to the static tank approach. Virtually any type of
experiment can be supported using this technique, as fish of any desired genotype can
be set up in pairs or smaller groups in a varying number of crosses. Because fish are
removed from holding tanks, the effects of behavioral hierarchies established in
holding tanks that can be counterproductive to breeding are negated. Static tank
technologies also allow for direct manipulation of water quality parameters; changes
in water chemistry, such as decreases in salinity, pH, and temperature, are thought to
promote spawning in fish adapted to monsoonal climate regimes (Murno, 1990).
These factors may also affect reproduction in zebrafish (Breder and Rosen, 1966).
There are drawbacks to static tank breeding strategies. Because the chambers are
off-flow, water quality conditions in the spawning setups deteriorate over time.
Although this has not been formally investigated, metabolites such as total ammonia
nitrogen and carbon dioxide accumulate in the water and are likely to have a negative
effect on spawning. Tanks may be flushed with fresh water to offset these potential
problems, but this represents added labor. Using static setups also necessitates that fish
are handled constantly, which may be a source of long-term stress for breeding
populations.
1.4 DETERMINING FACTORS FOR REPRODUCTION IN
LABORATORY STOCKS OF ZEBRAFISH
That zebrafish will readily spawn under a wide range of conditions in captivity has
undoubtedly played an important role in their rapid rise to prominence as a model
organism. This flexibility also suggests that there is considerable spread in repro-
ductive performance of laboratory stocks. Indeed, there are a number of key
husbandry factors that impact breeding efficiency, including water quality, nutrition,
behavior, and genetic management. A detailed understanding of how each of these
factors contributes to reproductive success is vital to maximizing production of
zebrafish in controlled settings. These concepts are touched upon briefly below. For a
more in-depth treatment of these subjects, see reviews by Lawrence (2007) and
Spence et al. (2008).
1.4.1 Water Quality
Zebrafish tolerate a wide range of environmental conditions in captivity. This
flexibility is a reflection of their distribution in the wild, as they are found across
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