M Raja, P Malaiammal, S
Nandagopal, M Muralidharan, and M Arunachalam, from the different institute of
the India. wrote a research article about, Genetic Diversity in Freshwater
Fish Genus Garra: A Comparative RFLP Analysis. Entitled, Comparative analysis
of genetic diversity among three species of the freshwater fish genus Garra
(Osteichthys: Cyprinidae) using restriction fragment length polymorphism. This
research paper published by the International Journal of Biosciences (IJB). an
open access scholarly research journal on Biosciences . under the
affiliation of the International Network For Natural Sciences | INNSpub. an
open access multidisciplinary research journal publisher.
Abstract
The genetic variation in three species of the freshwater cyprinid Garra was studied using the traditional morphometric, meristic and Restriction fragment length polymorphism as molecular tool analysis. Samples were collected from their respective geographic locations of southern Western Ghats. Based on the 46 morphometric and 18 meristic characters employed during this study 23 characters showed variation among the three species and hence were utilized for the PCA ordination. The principal component analysis was performed using 15 morphometric and 8 meristic characters of which 12 components were extracted and the first three axes showed eigenvalues >1 and they explained the variance about 81.46 % of the total variance. The genome size of the species Garra mullya ranged from 3.8-6.15 µg/mg, Garra kalakadensis ranged from 3.25- 6.3 µg/mg and Garra gotyla stenorhynchus ranged from 3.9- 6.15 µg/mg. Based on the electrophorogram, different bands of fragments in each lane and band volume were analyzed, According to Hind III enzyme the electrophorogram analysis showed maximum fragment length polymorphism in Garra mullya which had four fragments and the total volume of bands was 12.582 nmoles. Based on the Eco R1 enzyme digestion the electrophorogram analysis revealed that the maximum fragment length polymorphism in Garra mullya composed of four fragments and the total volume of bands in the entire lane was 10.5965 nmoles. Based on the Hind III and Eco R1 restriction enzymes, the cluster analysis clearly showed that the Garra mullya and Garra kalakadensis grouped together while Garra gotyla stenorhynchus with distinct geneticdistance did not cluster with the other two species. Garra gotyla stenorhynchus can also be distinguished morphologically from Garra mullya and Garra kalakadensis.
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Introduction
Fishes are the most
diverse group of living vertebrates, with more than 24,600 extant species
currently known. The Order Cypriniformes is the planet’s largest monophyletic
group of freshwater fishes, with over 400 genera and 3000 species native to
Asia, Europe, Africa, and North America (Nelson, 2006). Cypriniformes in
peninsular India is represented by 4 families, 8 sub families, 40 genera and
166 species. The family Cyprinidae has 4 subfamilies, 27 genera and 135 species
(Arunachalam et al., 2008). Historically the morphology of fishes is the main
source of information for taxonomic and evolutionary studies. Systematic
ichthyologists still rely on morphology for taxonomic characters as species
have characteristics shape, sizes, pigmentation patterns, disposition of fins
and other external features which help in identification and classification.
Meristic traits are often considered to be the most reliable taxonomic
characteristics, because most are easy to determine.
All the organisms are
subjected to mutations as a result of normal cellular operations or
interactions with the environment, leading to genetic variation. In conjunction
with selection and genetic drift, there arises genetic variation within and
among individuals, species and higher order taxonomic groups. This variation
are useful to geneticists, but it must be heritable and discernable to the
researcher, whether as a recognizable phenotypic variation or as a genetic
mutation distinguishable through molecular techniques. Several marker types are
highly popular in genetics.
The development of
molecular techniques has helped to investigate fish systematics. The realm of
methods developed for molecular studies offers new suites of characters for
analyzing relationships among fish systematics (Hillis, et al., 1996; Ferraris
and Palumbi, 1996) and hence have been effectively applied from the level of
populations to orders. A restriction fragment length polymorphism or RFLP, is a
variation in the DNA sequence of a genome that can be detected by breaking the
DNA into pieces with restriction enzymes and analyzing the size of the
resulting fragments by gel electrophoresis.
DNA-based techniques
for species identification have recently started to be applied towards a wide
variety of fish species, including closely related species belonging to the
same family or genus (Davidson 1998; Bossier 1999; Lockley and Bardsley 2000).
The information on genetic resource of Indian fish fauna is very limited,
especially native cyprinids. The genetic variation in different populations of
the freshwater cyprinid species Puntius filamentosus was studied using Restriction
Fragment Length Polymorphism (RFLP) analysis. The genomic size of the different
populations of P. filamentosus was found between 3.45 and 3.80ng/mg. The study
could prove one population as distinct. (Johnson et al., 2007).
The cyprinid fish genus
Garra includes bottom dwelling fishes usually found in fast flowing streams
where they cling to rocks using the highly modified mouth which acts as a
sucker. Garra is a common cyprinid and are mostly inhabitants of rapid running
waters, adapted with suctorial disc to attach themselves to the substratum in
swift currents and horizontally placed paired fins, especially the pectorals.
The flattening of the head and anterior part is as a result of efforts to
utilize more and more of the anterior part of the body for adhesion. The
proboscis and the tubercles help to lessen the velocity and impact of the
rushing torrents. Adaptive features in all the species being similar most of
the morphological features show overlap and hence the taxonomic characters
commonly used are not helpful in clear cut diagnosis of the species and hence
taxonomic ambiguities exist.
The genus is widely
distributed from southern China, across South East Asia, India and the Middle
East to northern and central Africa. Because of the extreme morphological
divergence of the genus Garra, the sister group relationships of this genus is
of extreme interest to systematic ichthyologists, fish biologists, and
evolutionary biologists alike.
In the present study,
the aim is to analyze the overall features of morphometric, meristic
characters, and Restriction pattern of nuclear DNA using the restriction
enzymes Hind III, and Eco RI regions in order to evaluate patterns of genetic
variation between species of Garra and to determine the phylogenetic relationship
of three species of the endemic genus Garra in selected streams and rivers of
the peninsular India.
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