農業部-水產試驗所全球資訊網農業部-水產試驗所全球資訊網

     近年臺灣文蛤人工養殖技術逐漸完備並推廣至民間業者，然而隨著養殖規模的 擴大，如生長停滯、偶發及季節性的大量死亡等問題也持續發生，是近年文蛤產量 甚穩定的主因，如105年8月於雲林縣臺西麥寮一帶養殖文蛤大量暴斃事件，其育成 率由原先的6至7成銳減為3成不到。前述問題初步推測可能原因為：季節轉換氣溫變 化劇烈、養殖密度過高造成之水質環境惡化等；目前市面上可見之養殖文蛤大致有 5物種，本計畫使用次世代定序技術(NGS)作為本研究基因遺傳分析之主要工具，並 針對最主要之養殖文蛤物種之轉錄體及共生菌展開研究，期能改善目前文蛤養殖遭 遇之相關問題，目前執行結果及後續預定辦理方向說明如下：

1.完成次世代定序的文蛤轉錄體序列，經由Function Annotator pipeline進行序列 註解(annotation)，再由NCBI Blastx等進行序列比對之結果，文蛤轉錄體 (transcriptome)其序列與現有相關軟體動物之序列資料相似度較低，最接 近之 大西洋牡蠣亦僅有33.6%之相似度，另經由序列分析，篩選出38個可能之熱休克蛋 白Heat Shock Protein 70 基因(HSP70)、29個可能之毒物代謝相關基因( Cytochrome P450)、及48個可能之細胞凋亡抑制基因Inhibitor of Apoptosis Protein(IAP)。

2.本年度預定對於文蛤轉錄體資料進行更進一步之分析，並整理相關序列並進行系 統樹研究等相關分析；另由文蛤個體萃取共生菌並進行metagenome(環境基因組 )分析內共生菌組成，其分析結果顯示，於腸道菌之組成上，野生個體以黴漿菌屬 (Mycoplasma spp.)為主，佔65至85%以上，養殖個體相較於野生個體更為複雜 ，且其組成除包含一般養殖常用之益生菌，如腸球菌屬(Enterococcus spp.)及乳 酸桿菌屬(Lactobacillus spp.)，且發現共生菌組成種類較多，具高多樣性，此 高多樣性成因可能為文蛤養殖池之施肥、相關益生菌於使用前再放大、及養殖池 原有之細菌所造成的，後續仍須進一步增加採樣地區及樣本數分析以進行進一步 瞭解。

     Hard clam, Meretrix spp. , are widely commercial aquaculture species in Asia. Various breeding programs, such as mass selection, family selection, and hybridization between different geographic populations, have been used in hard clam. Their growth and survival are often influenced by environmental factors, pathogen. However, the production of hard clam farming declined recently in Taiwan. Next-generation sequencing (NGS) can allow us to collect gene data and establish gene library much more quickly and cheaply than previous methods. In this project, genetic samples of hard clam from major farming area in Taiwan will be analyzed by NGS  and gene variation to explore the causes of declined production:

In this project:

1.Assembled sequences of hard clams transcriptome were annotated with Function Annotator pipeline. Several methods were used to infer their - 1 - 1082426 2. 1. 2. 1. potential functions. Briefly, assembled sequences were aligned to NCBI nr database with blastx program and potential coding regions were predicted with TransCoder program. The transcriptome of hard clam showed lower similarity of mRNA sequences of other Mollusca species, the highest is Pacific oyster with 33.6% by taxonomic distribution analysis. 38 candidates of heat shock protein genes (HSP70),  29 candidates of Cytochrome P450 gene, and 48 cadidates of inhibitor of apoptosis protein(IAP) gene were picked by sequence expression comparison.

2. The data of hard clam transcriptome will be studied deeper by phylogenetic method, etc in this year. On the other hand, the symbiotic bacteria of hard clam analyzed by metagenome method. Cultured hard clam showed high composition diversity and wild population showed similar composition pattern (mainly Mycoplasma spp.) in intestine. The composition of symbiotic bacteria were strongly affected such as food, and application of bacteria (Enterococcus spp. and Lactobacillus spp. etc...) in artificial environment. More studies are needed to provide a better knowledge and fully conclude on the effects of adding bacteria or "fertilization"  in clam aquaculture of Taiwan.