Bioscience Methods 2025, Vol.16, No.4, 173-182 http://bioscipublisher.com/index.php/bm 1 77 development of microsatellite markers has also revealed extensive allele diversity and high heterozygosity, which is of great significance for genetic variation monitoring and breeding projects (Luo et al., 2013). 5.2 Utilize genomic data to analyze the genetic relationships among different populations Genomic data, especially mitochondrial DNA (mtDNA) sequences, such as the cytochrome c oxidase subunit I (COI) gene, play an important role in clarifying the genetic relationships among O. marmorata populations. Studies on COI gene sequencing have shown that the domesticated population and the wild population in Indonesia have a close genetic relationship. Some individuals are exactly the same, while only very small genetic differences are shown among other individuals. This indicates that there is a recent differentiation or continuous gene flow between domesticated populations and wild populations (Table 1) (Syaifudin et al., 2021). Table 1 Identity percentage of nucleotide of marble goby (Adopted from Syaifudin et al., 2021) No. Species Origin Accession No. Identity (%) Samples code OMD3 and OMD2 1 Oxyeleotris marmorata Malaysia KT022088.1 9,951 2 Oxyeleotris marmorata USA AY722177.1 9,951 3 Oxyeleotris marmorata Indonesia KU692726.1 9,935 Sample code OMS3 1 Oxyeleotris marmorata Indonesia KU692726.1 100 2 Oxyeleotris marmorata Cambodia EF609424.1 100 3 Oxyeleotris marmorata Vietnam MH721190.1 99 Population structure analysis of Southeast Asia using mtDNA revealed multiple haplotypes, some of which were widely distributed while others were more limited. Molecular analysis of variance (AMOVA) shows that the differences between and within populations are significant, but the regional differences are small, indicating that genetic differentiation is not completely determined by geographical factors. Some populations (such as those in Ayutthaya, Dongnai and Sabah) have significant genetic differences, while populations in other regions such as Sarawak, Indonesia and western Malaysia are more similar. This reflects complex connectivity and isolation patterns. 5.3 The role of ecological isolation and gene flow in the genetic structure of species Ecological isolation and gene flow are the key factors shaping the genetic structure of O. marmorata. The high genetic diversity within the population and the lack of obvious population boundaries indicate that gene mobility is widespread, which may be the result of the joint promotion of natural diffusion and human migration (such as aquaculture) (Syaifudin et al., 2021). This gene flow helps maintain cross-regional genetic connectivity and reduces the possibility of local genetic differentiation. According to genetic analysis, due to ecological isolation or diffusion barriers, social populations show obvious genetic differentiation. Due to geographical or ecological barriers restricting gene flow, the populations of Ayutthaya, Dongnai and Sabah showed greater genetic differences (Ha et al., 2011). Gene flow usually helps promote genetic homogenization, but ecological isolation in specific regions may lead to the emergence of different genetic lineages, affecting the genetic structure and adaptation potential of snailfish. 6 Ecological Adaptation Mechanism 6.1 The influence of factors such as water quality, habitat and climate on the physiology of species The O. marmorata has remarkable physiological flexibility and can adapt to changes in water quality and salinity. The snailfish is mainly a freshwater species. It can help snailfish adapt to the Marine environment by up-regulating the proteins and enzymes related to osmotic regulation in the gills (such as Na+/K+ -ATPase and Na+:K+:2Cl− cotransporter). When salinity increases, maintaining ionic balance and plasma osmotic pressure (Chew et al., 2009). The O. marmorata also prevents the accumulation of ammonia by activating glutamine synthase in the liver and converting ammonia, thus enabling the O. marmorata to survive long-term exposure to the air. This process helps marble goby cope with fluctuations in oxygen levels and short-term exposure.
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