Abstract
Small abalone (Haliotis diversicolor) is a commercially valuable species for both fisheries and aquaculture. The production of annual farmed small abalone in Taiwan, once the highest in the world, has dramatically decreased in the past 15 years, and currently, the industry is close to collapse. Understanding the genetic diversity of small abalone and developing stock identification methods will be useful for genetic breeding, restoring collapsed stocks, managing stocks, and preventing illegal trade. We investigated 307 cultured and wild individuals from Taiwan, Japan, and Bali Island (Indonesia) by using the mitochondrial cytochrome c oxidase subunit I (COI) gene. Network analysis of mtDNA COI gene sequences revealed that the individuals collected from Taiwan, Japan, and Indonesia could be identified, and showed significant genetic divergence. In addition, the Indonesian population (Haliotis diversicolor squamata) was significantly different from the other populations and might need to be considered a separate species. We discovered a single nucleotide polymorphism marker in the mtDNA COI gene that can be used to distinguish the Taiwan population from the Japan population. We also developed a polymerase chain reaction-restriction fragment length polymorphism method for rapid detection. Furthermore, we could identify the cultured stocks, wild population, and hybrid stocks by using 6 microsatellites and amplified fragment length polymorphism. This study contributes useful tools for stock identification and the production of high-disease resistant small abalone strains (Japan × Taiwan or Taiwan × Japan). Efforts should be made to avoid unintentional random genetic mixing of the Taiwan population with the Japan population and subsequent breakdown of population differentiation, which impair local adaptation of the Taiwan wild population. Molecular markers revealed a split between the Taiwan and Japan populations, and the existence of a possible barrier to the free dispersal of small abalone is discussed.
Highlights
The abalone genus Haliotis is the sole genus in the Haliotidae family, with approximately 56 species worldwide [1,2]
Phylogenetic analysis was performed using partial mitochondrial c oxidase subunit I (COI) gene sequences (808 bp) from 307 individuals of small abalone, the H. diversicolor complex, including samples collected from 3 locations in Japan, 7 locations in Taiwan, and one location in Indonesia (Fig 1 and Table 1)
Eight clades were present in the Bayesian phylogenetic analysis, as follows: H. aliotis rubra, H. cracherodii, H. discus (H. discus discus and H. discus hannai), H. walallensis, H. kamtschatkana complex (H. kamtschatkana assimilis, H. kamtschatkana kamtschatkana, and H. sorenseni), H. tuberculata (H. tuberculata tuberculata and H. tuberculata coccinea), H. diversicolor complex (H. diversicolor diversicolor, H. diversicolor supertexta, and H. diversicolor aquatilis), and H. diversicolor squamata (Fig 2)
Summary
The abalone genus Haliotis is the sole genus in the Haliotidae family, with approximately 56 species worldwide [1,2]. These species are widely distributed in temperate and tropical coastal. 14 abalone species are economically valuable for fishery production and aquaculture; most of them possess a large body and are distributed in temperate seas [4,5]. In 2007, the total production of cultured abalone in China exceeded 20,000 tons, estimated to be worth CNY 50 billion (USD 8.2 million) annually, and nearly 60% of the output was produced on the coasts of southern China, Fujian Province [8]. In 2013, China had more than 300 operating abalone farms, with the largest individual farm producing more than 90,694 tons annually, and either H. discus hanni or a hybrid between H. discus hanni and H. discus discus accounted for nearly 95% of abalone production [15]
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