International Journal of Marine Science, 2025, Vol.15, No.2, 92-106 http://www.aquapublisher.com/index.php/ijms 97 the genetic background of breeding groups in various places tends to be similar. The study found that the Pacific white shrimp population cultivated in different Asian countries has little difference in genetic markers such as microsatellites, and many of them originated from the offspring of the first batch of American-born shrimp. Long-term high-intensity artificial selection and incomparison also trigger germplasm degeneration: manifested as decreased growth rate, weakened disease resistance, and reduced fertility. At the end of the 20th century, the incidence and mortality of shrimp in some breeding areas in China increased year by year, which is believed to be related to germplasm aging. In response to these issues, Asian countries have begun to pay attention to genetic improvement and variety updates. On the one hand, since the 2000s, many countries have launched a breeding program for good breeding, cultivate new strains with fast growth and strong disease resistance through hybridization and family breeding, and introduce new wild germplasm to rejuvenate domestic groups. On the other hand, strengthen international cooperation and introduce new SPF pro-shrimps from origin or other countries to expand the gene pool (Li et al., 2024). 4.2.3 Communication dynamics and limiting factors to Africa and the Middle East Under the demonstration effect of successful breeding in Asia, Whiteleg shrimp have gradually spread to Africa and the Middle East since the 21st century, becoming new breeding targets. However, this diffusion process is relatively slow, and its dynamics and limiting factors are worth discussing. In terms of power, the first is market-driven: With the growth of global demand for shrimp, some African coastal countries hope to develop shrimp farming to obtain export benefits, and have introduced the high-yield species of Pacific white shrimp (Tian et al., 2024). The second is technology promotion: Asian experts and enterprises bring breeding technology and management experience to Africa and the Middle East to help local infrastructure and technical teams. This "technical spillover" reduces the difficulty of starting a new region. In terms of restrictive factors, environmental conditions restrict: Whiteleg shrimp is suitable for tropical and subtropical warm waters, and in some areas of Africa introduced (lower water temperature or unstable climate) must overcome the problems of wintering and breeding cycles (Wang et al., 2020). Secondly, seedling supply bottlenecks: African and Middle Eastern countries lack local pro-shrimp cultivation systems, and often require airlifting shrimp from Asia or the Americas from a long distance, which is costly and has a high risk of mortality in the process. Disease prevention and control challenges: New breeding areas often have no history of shrimp farming and lack experience in quarantine and disease monitoring. If the virus is carried into the local waters during the introduction process, it may cause serious consequences (such as reports of white spot disease and other transmission into Africa). In fact, the first introduction in some countries has failed due to disease outbreaks. Finally, manpower and supporting: farming shrimp requires supporting support such as feed, power supply, and technicians, while some African countries have weak foundations in these aspects, which restricts the large-scale development of the industry (Pratiwi et al., 2021). Despite the above difficulties, South American whitening prawns have made some progress in Africa and the Middle East in recent years. 4.3 The spread mode of giant tiger shrimp (Penaeus monodon) in Asia and Africa Giant tiger shrimp (i.e., Giant tiger prawn) is an important traditional breeding species in the Asia-Pacific region. Its transmission history is different from that of Whiteleg shrimp and has its own characteristics. The Giant tiger prawns are native to Southeast Asia to northern Australia and were mainly cultivated in extensive manner before the second half of the 20th century in native countries (such as Thailand, the Philippines, Indonesia, India, etc.). In the 1970s, Japan took the lead in conquering the full artificial seedling cultivation technology of prawns, releasing larvae to pond breeding, and driving Asian neighbors to imitate (Wong et al., 2021). In the following decades, the Giant tiger prawn farming technology spread throughout East and Southeast Asia, making it the highest-growing shrimp species in Asia in the early 1990s. However, unlike Vannephrod, the cross-continental transmission of the pimples is relatively limited. Until around 2000, only a few African countries (such as Madagascar and Mozambique) introduced prawns to breed them. Its propagation mode mainly presents two paths: one is propagation within the region. Seedlings and shrimps are frequently exchanged between Southeast Asian countries and Taiwan, China, to form an "Asian germplasm circle". Due to the similar geographical location, this transmission is relatively easy, resulting in little genetic differences in the prawn populations of the sputum in
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