International Journal of Marine Science, 2025, Vol.15, No.2, 92-106 http://www.aquapublisher.com/index.php/ijms 100 brought by international trade. Viruses, bacteria and parasites that are susceptible to shrimps can spread with the cross-border flow of live and fresh shrimps. The most prominent examples are the transcontinental transmission of prawns, white spot syndrome virus (WSSV) and Taola virus (TSV). TSV was originally only popular in the Americas, but with the introduction of Pacific white shrimp into Asia, shrimp seedlings that were infected around 1998 were introduced to Thailand, Taiwan, China and other places, resulting in a large-scale outbreak. The transmission path is believed to be caused by the transnational sale of infected shrimp seedlings. WSSV spread from Asia to the Americas in the 1990s, devastatingly hitting the shrimp industry in Ecuador and other countries. Research evidence shows that WSSV's global popular strains can be traced back to a few sources, and international seedling trade has accelerated its global spread (Figure 3) (Tandel et al., 2017). The mechanisms of co-dispersal of international trade in co-dispersal include: the export of seedlings carrying pathogens/shrimp-producing shrimps, the release of contaminated water bodies for transporting seedlings, and the entry of fresh product waste into the environment. Since shrimp seedlings require water medium transportation, pathogens can be hidden in water and cross-border (Prochaska et al., 2022). Figure 3 WSSV infection in tiger shrimp (P. monodon)(a) Normal tiger shrimp; (b) WSSV-infected tiger shrimp (note the whitespots on the carapace, broken antennae and pareopods) (Adopted from Tandel et al., 2017) 6 Genetic Diversity Pattern and Molecular Ecological Signals 6.1 Application of mitochondrial DNA and microsatellites in geographic population research By analyzing the mitochondrial DNA sequences and nuclear microsatellite markers of the population, the genetic diversity pattern of shrimp geographical populations can be revealed. Mitochondrial DNA is often used to analyze historical expansion and lineage geographical structure due to its single parent inheritance and small effective population size. Haplotype composition of mitochondrial COI sequences in different regions can indicate whether the population has experienced expansion bottlenecks. Studies show that the COI haplotypes in Chinese shrimp wild populations along the coast of China are highly diverse, while the number of haplotypes in artificial breeding populations is significantly reduced, indicating that the breeding process may have lost some haplotypes. Microsatellites (SSRs) are highly polymorphic loci in the nuclear genome because high mutation rates are suitable for reflecting recent gene flow and inbred conditions. Microsatellite analysis is also used to detect confounding
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