Abstract
The Manila clam Ruditapes philippinarum is the world’s second most important bivalve mollusk commercially farmed, whose indigenous populations are mainly distributed in the coastal areas of East Asia. However, with the development of commercialization, mixture of populations and loss of local germplasm have become prominent problems. Here, genetic differentiation of seven Manila clam populations from East Asia was investigated through analyzing the polymorphism of the mitochondrial cytochrome C oxidase subunit I (COI) gene as well as 20 simple sequence repeat (SSR) molecular loci. In total, 40 haplotypes were identified, among which 31 were unique. Moreover, two main haplotypes were detected with several radiating derived haplotypes. Populations in Japan-North Korea shared haplotype Hap_31, and populations in China shared haplotype Hap_7, suggesting that the natural geographical isolation of the Yangtze River and the Yalu River might have divided the East Asian indigenous populations into three groups, which were located in South China, North China, and Japan-North Korea, respectively. The Aquaculture breeding activities from South to North in China might have promoted gene exchange among Manila clam populations. Population in Laizhou had the highest genetic diversity and therefore could be an excellent germplasm source.
Highlights
The Manila clam Ruditapes philippinarum[1] is a eurythermal and euryhaline species
Cordero et al.[6] combined the mitochondrial cytochrome C oxidase subunit I (COI) gene sequence and/or the simple sequence repeat (SSR) gene marker to assess the genetic basis of the Manila clam population introduced from Japan to the North American west coast in 1936
Nine closely related COI haplotypes were clearly present among the East Asian populations (Fig. 1), and unique haplotypes were detected as well
Summary
The Manila clam Ruditapes philippinarum (synonym Venerupis philippinarum)[1] is a eurythermal and euryhaline species. In 1936, the Manila clam was introduced from Japan to British Columbia and subsequently from North America to the European coasts of France, Britain, Italy, Spain, and Turkey Because it is characterized by long larval floating time (2–3 weeks), widespread distribution, and strong environmental adaptability, it is widely distributed and has become the world’s second most important commercially cultured bivalve mollusk[1,2,3,4,5]. In recent years the northern coastal ecosystems of China have been impacted by economic development, frequent commercial activities, land reclamation from the sea, and artificial breeding of Manila clams using seedlings from southern China These changes have resulted in mixing of the Manila clam populations and loss of the indigenous germplasm, which have prompted studies of Manila clam population gene exchange and genetic structure changes. Our results provide a hints for the conservation and utilization of Manila clam germplasm resources
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