Eichner Christiane, Hamre Lars Are, Nilsen Frank
SLCR-Sea Lice Research Center, Department of Biology, University of Bergen, Thormøhlensgt. 55, 5008 Bergen, Norway.
SLCR-Sea Lice Research Center, Department of Biology, University of Bergen, Thormøhlensgt. 55, 5008 Bergen, Norway.
Parasitol Int. 2015 Feb;64(1):86-96. doi: 10.1016/j.parint.2014.10.006. Epub 2014 Oct 16.
The salmon louse (Lepeophtheirus salmonis) is an ectoparasitic copepod causing severe problems to the fish farming industry and to wild salmonids. Morphologically, all stages in the life cycle of L. salmonis have been described in detail based on successive samples from host populations. However, the rate of development differs between males and females as well as between individuals. It has therefore been difficult to observe development within stages, and this has led to a longstanding misinterpretation of the number of chalimus stages. Here samples of chalimi obtained for 12 consecutive days were observed daily in incubators. Chalimus 1 was able to molt in incubators only when fully grown and close to molting, whereas chalimus 2 was able to molt at about 60% of total instar growth. Total length instar growth was about 35% in both chalimus 1 and chalimus 2 and about equal among males and females; the cephalothorax increased by about 12% and the posterior body by about 80%. Instar growth was probably the main factor that led to the former belief that L. salmonis had four chalimus stages. Relative total length increase at molting was at the same order of magnitude as instar growth, but total length of females increased significantly more than that of males at molting. Consequently, a sexual size dimorphism was established upon molting to chalimus 2 and males were about 10% smaller than females. While growth by molting was mainly caused by cephalothorax increase, instar growth was mainly due to increase of the posterior body. The cephalothorax/total length ratio decreased from beginning to end of the instar phase suggesting that it may be used as an instar age marker. Male and female chalimus 2 can almost uniquely be identified by cephalothorax length. Chalimus 1 lasted between 5 and 6 days for males and between 6 and 7 days for females at 10°C. Chalimus 2 males lasted between 6 and 7 days and females between 7 and 8 days.
鲑鱼虱（Lepeophtheirus salmonis）是一种体外寄生桡足类动物，给养鱼业和野生鲑科鱼类带来严重问题。在形态学上，基于从宿主种群中连续采集的样本，已经详细描述了鲑鱼虱生命周期的所有阶段。然而，雄性和雌性以及个体之间的发育速度有所不同。因此，很难观察阶段内的发育情况，这导致了对沙利姆期数量的长期误解。在这里，在孵化器中每天观察连续12天获得的沙利姆样本。沙利姆1只有在完全生长并接近蜕皮时才能在孵化器中蜕皮，而沙利姆2在总龄期生长约60%时能够蜕皮。沙利姆1和沙利姆2的总长度龄期生长约为35%，雄性和雌性之间大致相等；头胸部增加约12%，后体增加约80%。龄期生长可能是导致以前认为鲑鱼虱有四个沙利姆期的主要因素。蜕皮时相对总长度的增加与龄期生长处于同一数量级，但蜕皮时雌性的总长度增加明显多于雄性。因此，在蜕皮到沙利姆2时建立了性大小二态性，雄性比雌性小约10%。虽然蜕皮生长主要是由头胸部增加引起的，但龄期生长主要是由于后体的增加。头胸部/总长度比在龄期阶段从开始到结束逐渐降低，这表明它可能用作龄期标记。雄性和雌性沙利姆2几乎可以通过头胸部长度唯一地识别。在10°C时，雄性沙利姆1持续5至6天，雌性持续6至7天。雄性沙利姆2持续6至7天，雌性持续7至8天。
