International Journal of Aquaculture, 2015, Vol.5, No.23 1
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et al., 2007; Perez-Enriquez et al., 2009; Souza De
Lima et al., 2010.
A significant decrease in all parameters that involve
quality of alleles has been proved when compared the
first introduction (S0-1) with its tested descendants,
but not among them (Table I for values and significan-
ces and Figure 1 for tendency). Cruz et al., 2004,
assessed the genetic variability through consecutive
generations (named G0, G1 and G2) in a two year
Shrimp Breeding Program. They did not find differences
in allele frequencies between G0 and G1, but they did
between G1 and G2. Besides, a discrete decreasing
tendency in effective allele number, but not in allele
number, is observed. In general, as well as Luvesuto et
al., 2007 in Brazil for the same species,
P. vannamei
,
both groups of researchers did not detect genetic
diversity reduction after three successive generations.
Those authors characterized generations 5
th
, 6
th
and 7
th
of a closed and reared line of this species using four
microsatellite regions. In a further work, Perez-Enriquez
et al., 2009 did not find a decrease in the number of
alleles between a 2000-2002 pool and the 2007 (a six
to eight generation differences), but slight increase in
this absolute number. Let’s note that although two of
the loci, Pvan1758 and Pvan1815 (Cruz et al., 2002)
were used in the previous work, in the further one;
more new
loci
(TUMXLv8.256, TUMXLv10.312,
TUMXLv9.103 and Lvan05) have been also used in
this genetic status characterization of the cultured
species in Mexico. Finally, Vela-Avitúa et al., 2013,
using 26
loci
and pedigree information, detected a
decline in genetic parameters such as He, Na, Ne from
a wild population to two captive generations (named
GEN07 and GEN09), but those values however are
similar between the one year different generations.
When using effective population sizes based both in
microsatellite and pedigree, a decline trend, even
when was not significant between GEN07 and GEN09
was found.
Then, the question about the origin history of every
stock that has entered into Cuba to be cultured is
emerged. The answer will be inevitably uncertain
since all the introductions have been bought knowing
that here we have Specific Pathogen Free (SPF) shrimps
and nothing else (except for the first introduced stock
that it is known that has been genetically manipulated
for high growth). This have been extremely helpful in
preventing viral diseases occurrences in Cuba (Artiles
et al., 2011b), but do not let to figure out about the
previous history, as it would be the case of brood
stock obtained from natural areas. So, the present S0-1,
with the rest four introduced stocks from SIS,
constitutes the founder stock of
P. vannamei
in Cuba.
This fact is consistent to the panorama showed in
PCoA analysis (Figure 3), and to the assignation exercise
accomplished in Pérez-Beloborodova et al., 2012.
In addition to the absence of data about the previous
history of the bought introductions (in that case before
S0-1), there is more lack of information between this
stock and its first descendant generation, due to no
genetic analyzes were made at that time and neither
samples were preserved. And so, taking into a
consideration the processed data, there is an evident
loss of alleles between the first introduced stock and
its second generation pool. We cannot realize however
if this loss was produced at that time or in a previous
step, it is in S1-1. The non-analyzed data among the
S2-1 and S9-1 seems not to have relevant meaning,
because all the values remain similar for each
subsequent descendants tested populations.
2.3 Inbreeding, Bottleneck effect and Relatedness
coefficient of the first introduced stock of
P. vannamei
in Cuba for culture and three descendants.
In aquaculture, the mating among relatives is a
common phenomenon that is not injurious itself, but
its accumulation over generations could induce the
expression of deleterious alleles once they are paired
as recessives in homozygosis. This inbreeding depression
could induce a decrease in productive performance
traits, such as growth rate, survival, disease susceptibility
as have been widely report in literature,
e.g
: (Sbordoni
et al., 1986; Benzie, 2000; Bierne et al., 2000a; Bierne
et al., 2000b; Hulata, 2001)
The evaluation of genetic diversity and inbreeding is
so a potent tool for producers through all the process.
The creation of genetic programs that help in taken
choices for best crossings and breeders is a widely
used strategy over the world. The inbreeding coefficient,
Fis, is a measure of the intraspecific variation among
populations, and so, an indirect extent of consanguinity.
Positive values that are obtained in this work (Table 2)
are indicative of heterozygous deficit as have been
shown by most of the authors that have calculated it
