刺参养殖池塘中新敌害生物澳洲异尾涡虫的鉴定及其危害

为了对导致辽宁大连、山东东营的2家养殖场池塘养殖刺参大量化皮死亡的新的敌害生物进行鉴定并确定其对养殖刺参的危害。本实验通过形态学观察、分子鉴定及系统发育分析确定了涡虫的分类地位,通过生态学方法确定了其生态适应条件,通过切割后培养的方法观测了其再生能力,通过与刺参苗种的共培养实验测试了该物种对刺参的危害及其危害方式。形态学观察结果显示,该涡虫体长0.96～3.26 mm,体宽0.49～1.93 mm,外观黄色或黄褐色,头部钝圆,具一对暗红色棒状眼点,尾部具两条并列的尾垂;显微镜镜检发现其表皮下分布密集的虫黄藻,体表周生纤毛,雌雄同体,口后具有两个生殖孔;对该物种COⅠ及18S r DNA基因片段扩增测序结果进行分析,并构建基于18S rDNA基因的系统发育树,结果显示该生物与澳洲异尾涡虫序列同源性达99.64%,根据其形态学特征,并结合18S rDNA分子鉴定结果,将该生物鉴定为澳洲异尾涡虫;进一步对其生活习性进行了研究,结果显示,该生物具有避光性,其适宜温度为18～24°C,适宜pH为5.5～8.0,适宜盐度为20～40;再生实验表明,该物种具有很强的前后轴极性再生能力;该生物与刺参的共培养实验表明,澳洲异尾涡虫对刺参体表表现出很强的趋向性,可以吸附在刺参体表导致刺参苗种溃疡、化皮甚至死亡,但刺参的体腔、肠道、呼吸树内均未发现虫体寄生。研究表明,澳洲异尾涡虫是营自由生活的池塘养殖刺参的一种新的敌害生物,在养殖过程中需要密切关注并防范该敌害生物。

Identification of Heterochaerus australis as a new enemy species in the cultured ponds of Apostichopus japonicus and its harm

There was an outbreak of Bacterial Ulceration Syndrome (BUS) of Apostichopus japonicus in two culture ponds located in Dalian, Liaoning Province and Dongying, Shandong Province, in October 2019. Epidemiological investigation detected a kind of free-living turbellarians in the culture system including the body surface of A. japonicus, the water and the sediment. Morphological observation of this species revealed that the body length ranged from 0.96 to 3.26 mm and the body width range from 0.49 to 1.93 mm. The body color was yellow or yellowish-brown. Its head was blunt round shape, with a pair of dark red rodlike ocellus. Two caudal lappets lay coordinately on both sides of its tail.Microscopic examination revealed that symbiotic Zooxanthella within the epidermis and its body was covered with cilia. It was hermaphrodite, with two genital openings behind the mouth. The 18S rDNA gene sequence showed 99.64% identity with Heterochaerus australis. Based on the morphological and genetic analysis, it was identified as H. australis. The ecological study showed that this species was photophobic, its suitable temperature was 18-24 °C, its suitable pH was 5.5-8.0 and its suitable salinity was 20-40. This species also showed strong ability of polar regeneration. The co-cultivation experiment of this species and A. japonicus showed that H. australis can adsorb on the surface of sea cucumber, causing ulceration on the body wall and eventually the death of sea cucumber. However, there was no parasitic phenomenon in the body cavity, intestine and respiratory tree of the sea cucumber. All the results indicate that H. australis is a new enemy species for A. japonicus in pond culture.