苗期中国对虾幼体异养细菌区系及其变化与病害发生的关系

研究了2个育苗场不同发育期的中国对虾(Penaeus chinensis)幼体的异养菌和弧菌种群变化的动态过程。以典型特征法、BIOLOGGN法和数值分类法对菌株进行鉴定。结果表明，对虾幼体样品中所分离的细菌，大多是革兰氏阴性杆菌。鉴定为假单胞菌属(Pseudomonas)、气单胞菌属(Aeromonas)和弧菌属(Vibrio)。弧菌属主要为溶藻弧菌(Vibrioal-ginozyticus)和哈维氏弧菌(Vibrio harveyi)。在对虾幼体发育早期，假单胞菌(Pseudomonas)和气单胞菌(Aeromonas)占优势，随着对虾幼体的发育，弧菌(Vibrio)渐成为优势，其中溶藻弧菌(Vibrio alginolyticus)和哈维氏弧菌(Vibrio harveyi)优势明显。二者的消长与苗期病害的发生相关，溶藻弧菌总是在虾幼体健康时出现或成为优势，而哈维氏弧菌成为优势时，苗期病害容易发生。

Study of Heterotrophic Bacterial Flora, Dominant Vibrios Composition of Larvae and Postlarvae of Penaeus chinensis and Its Relationship with Disease

The numbers of heterotrophic bacteria (the mean bacterial count on ZoBell's 2216E agar) and vibrios (on TCBS plate) from larvae and postlarvae of Penaeus chinensis were found to vary between different growth stages. Only a few bacteria were found in nauplii. The total viable bacterial count of each larva increased gradually from stage nauplii to postlarvae except fluctuating number of Zoea 3 or Mysis 1. Almost the same level of bacterial populations was obtained from the same stage larvae examined in different tanks in Dahua hatchery. Bacteria isolated from the samples were predominantly Gram-negative. The generic composition, especially the composition of vibrios species were found to vary from stage to stage. Pseudomonas and Aeromonas were the most frequently isolated genera from larvae at the initial stages, followed by Vibrio alginolyticus and Vibrio harveyi at the following stages subsequently. The high prevalence of vibrios, especially V. alginolyticus and V. harveyi, were isolated frequently from healthy larvae and postlarvae of P. chinensis. It suggested that V. harveyi emerging ahead of time due to the worse quality of rearing water was the one factor leading to epizootic occurrence.