Mass mortality due to necrosis signs occurred in hatchery-reared zoea stage larvae of the mud crab Scylla serrata in Okinawa, Japan, and a causative bacterium was isolated. In this study, we identified and characterized the bacterium by genome analysis, biochemical properties and pathogenicity. The bacterium was a Gram-negative, non-motile, long rod, forming yellow colonies on a marine agar plate. It grew at 20-33°C (not at 37°C) and degraded chitin and gelatin. Phylogenetic analysis of the 16S rRNA gene sequence identified the bacterium as Aquimarina hainanensis. Genome sequence data obtained from Illumina MiSeq generated 29 contigs with 3.56 Mbp in total length and a G + C content of 32.5%. The predicted 16 chitinase genes, as putative virulence factors, had certain homologies with those of genus Aquimarina. Experimental infection with the bacterium conducted on larvae of four crustacean species, brine shrimp Artemia franciscana, freshwater shrimp Caridina multidentata, swimming crab Portunus trituberculatus and mud crab S. serrata, revealed that this bacterium was highly virulent to these species. The present study suggests that the bacterium caused mass mortality in mud crab seed production was A. hainanensis and can be widely pathogenic to crustaceans.

中文翻译：

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从孵化场中患病蟹蟹Scylla serrata幼虫中分离出的海南海产Aquimarina的特征。

在日本冲绳的泥蟹Scylla serrata的孵化场的zoea阶段幼虫中，由于坏死征兆而导致大量死亡，并分离出致病细菌。在这项研究中，我们通过基因组分析，生化特性和致病性鉴定并鉴定了细菌。该细菌是革兰氏阴性，不能移动的长杆，在海洋琼脂平板上形成黄色菌落。它在20-33°C（而不是37°C）下生长，并降解了几丁质和明胶。对16S rRNA基因序列进行系统进化分析，确定该细菌为海南海产阿基里纳菌。从Illumina MiSeq获得的基因组序列数据生成了29个重叠群，总长度为3.56 Mbp，G + C含量为32.5％。预测的16种几丁质酶基因作为推定的毒力因子，与阿奎玛丽娜属具有某些同源性。在四种甲壳类动物的幼虫上进行的细菌实验感染，盐水虾卤虫Artemia，淡水虾Caridina multidentata，游泳蟹Portunus trituberculatus和泥蟹S. serrata，表明该细菌对这些物种具有高度毒性。本研究表明，该细菌在泥蟹种子生产中引起大量死亡，是海南曲霉，对甲壳类动物具有广泛的致病性。