Journal of Marine Sciences ›› 2018, Vol. 36 ›› Issue (1): 86-92.DOI: 10.3969/j.issn.1001-909X.2018.01.009

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Identification of bacterial infections associated with larval development of Yesso scallop

LIU Ji-chen1,3, JIN Xiao-jie*1, LI Ming2, CHEN Juan1, GUO Zong-ming1, MA Yue-xin3   

  1. 1. Department of Food,Yantai Nanshan University, Yantai 265713, China;
    2. Zhangzidao Group Co., Ltd., Dalian 116001, China;
    3. Dalian Ocean University, Key Laboratory of Mariculture & Stock Enhancement in North China's Sea, Ministry of Agriculture, Dalian 116023, China
  • Received:2017-09-28 Revised:2017-12-29 Online:2018-03-15 Published:2022-11-21

Abstract: The pathogens causing mortality in Yesso scallop (Patinopecten yessoensisis) larvae in the hatchery of Zhangzidao Group Co. Ltd. were identified. A high mortality of the Yesso scallop larvae occurred during the seedling process: the larvae lost their ability to swim, their cilia fell off and their valves closed, they then sank to the bottom of the nursery pond and died. Vibrio has been reported as the primary pathogen for massive mortalities of different bivalves both in hatchery and in the field worldwide. Total viable vibrios counts in moribund larvae were 1.12×104 CFU/g on Tryptone Citrate Bile Sucrose agar plates. Two dominant strains, named V1 and V2, accounted for 64.3% and 32.1% of total vibrios counts respectively. Blood agar plates were used to measure hemolysis of isolated strains. Strain V1 exhibited beta hemolysis, while strain V2 exhibited alpha hemolysis. A challenge test showed that the signs of infected larvae were identical to those of natural moribund larvae, the cumulative mortality caused by strains V1 and V2 was significantly higher than that of the control (P<0.05) and bacteria were re-isolated from the dead larvae. Strains V1 (GenBank Accession No: KR232924) and V2 (GenBank Accession No: KF232925) shared 99.9% and 99.2% identity with Vibrio splendidus ctt 31/5 and Vibrio tasmaniensis 007, respectively, by 16S rDNA sequencing. The presence of genes coding for virulence factors was examined by PCR analysis, showing that strain V1 possessed the extracellular metalloprotease (vsm) gene. Antibiotic susceptibility assays showed that both strains were sensitive to the rifampicin, florfenicol and sulfafurazole.

Key words: Patinopecten yessoensis larvae, bacterial pathogen, Vibrio splendidus, Vibrio tasmaniensis

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