Maran Balu Alagar Venmathi, Moon Seong Yong, Ohtsuka Susumu, Oh Sung-Yong, Soh Ho Young, Myoung Jung-Goo, Iglikowska Anna, Boxshall Geoffrey Allan
Marine Ecosystem Research Division, Korea Institute of Ocean Science & Technology, P.O. Box 29, Seoul 425-600, Korea.
Parasite. 2013;20:15. doi: 10.1051/parasite/2013015. Epub 2013 May 7.
The developmental stages of the sea louse Lepeophtheirus elegans (Copepoda: Caligidae) are described from material collected from marine ranched Korean rockfish, Sebastes schlegelii. In L. elegans, setal number on the proximal segment of the antennule increases from 3 in the copepodid to 27 in the adult. Using the number of setae as a stage marker supports the inference that the post-naupliar phase of the life cycle comprises six stages: copepodid, chalimus I, chalimus II, pre-adult I, pre-adult II, and the adult. We observed variation in body length in both of the chalimus stages which we consider represents an early expression of sexual size dimorphism. We interpret the larger specimens of chalimus I as putative females, and the smaller as putative males; similarly with chalimus II, larger specimens are putative females and the smaller are males. Two patterns of life cycle are currently recognized within the Caligidae but the evidence presented here reconciles the two. We conclude that the typical caligid life cycle comprises only eight stages: two naupliar, one copepodid, and four chalimus stages preceding the adult in Caligus, but with the four chalimus stages represented by two chalimus and two pre-adult stages in Lepeophtheirus. This is a profound change with significant implications for the aquaculture industry, given that lice monitoring protocols include counts of chalimus stages and use temperature to predict when they will moult into the more pathogenic, mobile pre-adults. Lice management strategies must be tailored to the precise life cycle of the parasite.
从韩国海水养殖的许氏平鲉（Sebastes schlegelii）身上采集的材料描述了秀丽海虱（Lepeophtheirus elegans，桡足纲：鱼虱科）的发育阶段。在秀丽海虱中，触角近端节上的刚毛数量从桡足幼体阶段的3根增加到成体阶段的27根。将刚毛数量用作阶段标记支持了这样的推断，即生命周期的无节幼体后期阶段包括六个阶段：桡足幼体、第一期挂幼、第二期挂幼、第一期准成体、第二期准成体和成体。我们观察到两个挂幼阶段的体长存在差异，我们认为这代表了性大小二态性的早期表现。我们将较大的第一期挂幼标本解释为推定的雌性，较小的标本解释为推定的雄性；第二期挂幼阶段情况类似，较大的标本是推定的雌性，较小的是雄性。目前在鱼虱科中公认有两种生命周期模式，但此处提供的证据使这两种模式达成了一致。我们得出结论，典型的鱼虱生命周期仅包括八个阶段：在锚头鱼虱属中有两个无节幼体阶段、一个桡足幼体阶段和四个在成体之前的挂幼阶段，但在海虱属中，四个挂幼阶段由两个挂幼阶段和两个准成体阶段代表。鉴于鱼虱监测方案包括挂幼阶段的计数，并利用温度来预测它们何时会蜕皮成为更具致病性、可移动的准成体，这是一个具有深远影响的重大变化，对水产养殖业意义重大。鱼虱管理策略必须根据寄生虫的确切生命周期进行调整。
