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International Journal of Marine Science 2015, Vol.5, No.5: 1-8
http://ijms.biopublisher.ca
2
(Palma and Andrade, 2002; Aktas et al., 2006),
ontogeny (Hard et al., 1999; Debowski et al
.
, 1999)
and functional morphology (Dean et al., 2006). The
transformed truss measurements were subjected to
factor analysis and classify by cross-validation of
discriminant analysis (Sen et al., 2011).
Published studies on genetic variation of
P. semisulcatus
populations are limited compared to other commercially
important shrimp species but few studies have been
documented under different aspects such as taxonomic
identification (Saad et al., 2013; Khamnamtong et al.,
2005) and population structure analyses (Rezvani et
al
.
, 2001; Niamaimandi et al
.
, 2010). Utility of
different gene regions in population and phylogenetic
studies are important as genes evolve at different rates
and thus exhibit different evolutionary patterns
(Munasinghe et al
.
2003). Past studies have been
revealed that mitochondrial DNA (mtDNA) and
nuclear DNA (nucDNA) evolve in different rates
(Avise, 1994; Hartl and Clark, 1997). Therefore,
pattern of genetic divergence among populations
should be assessed using differently evolving gene
regions for proper identification of different stocks
in the wild.
Taxonomic studies on
P. semisulcatus
populations in
Sri Lanka have not been reported so far. However,
intensive exploitation of shrimps of the genus
Penaeus
is causing a decline in per unit landings in many areas
of the seas around the world from the past (Rao et al
.
,
1993) to the present (Mehanna et al
.
, 2012). Therefore,
identifications of stocks in different landing sites of the
island may help for conservation of these species and
sustainable management of the fishery industry. The
aim of the present study was to investigate pheneotypic
and genotypic variation of geographically separated
two wild
P. semisulcatus
populations in Sri Lanka.
2 Materials and Methods
The locations of the two populations are geographically
widely separated and situated at the extreme ends of
the northern and southern parts of the island (Figure 1).
According to the past investigations, two locations
consisted with different environmental conditions
(Silva et al., 2013). Samples were collected from two
wild populations: Jaffna lagoon and Walawe River
estuary (Figure 1). From each site, samples were
collected from at least three sub sampling locations
and pooled to make the final sample of the population.
Approximately 70 individuals of adults were
randomly selected from the collection of each
population. Males and females were separated
according to the structural differences of sex organs
(petasma and thelycum). Forty two morphometric
measurements were collected as described by Aktas et
al., (2006) according to the truss network system
(Figure 2). Collected data were log transformed and
those skewed from normality test were omitted from
further analysis.
Figure 1 Two Sampling sites of the current study
Figure 2 Morphometric characters used in the truss network
measurements (Aktas et al., 2006)
Significant differences between sexes for all parameters
within each population were determined by comparison
of means using t test. Parameters that did not show
significant differences between sexes for both
populations were selected and thus males and females
were combined (P>0.05). Finally, twenty one
morphometric measurements were used to continue
the analysis. To perform the multivariate analysis, all
measurements were standardized using regression and
residual analysis method (Thorpe, 1976). Discriminant