Evolution and adaptation of the eels, genus Anguilla

在1995-1998财政年度期间，我们对12个国家进行了为期540天的考察，并取得了以下成果。1.适应意义：（1）生理特性：免疫组织化学分析显示，日本鳗鲡鳃板和鳃丝中存在两种类型的氯细胞。前者在淡水栖息地被激活，后者在下游迁移到海洋后的海洋栖息地被激活。(2)迁移行为：1995-1998年对印度尼西亚苏拉威西岛波伊加河口的热带玻璃鳗进行了调查，发现有3种玻璃鳗（A.celebesensis、A.marmorata和A.bicolor pacifica）出现在苏拉威西岛波伊加河口。前两者几乎全年都有迁移，高峰期在6月，最后一次发生在1月，三月，4月，十月和十二月。对耳石显微结构和Sr/Ca比值的分析表明，热带鳗鲡在孵化后90-160天开始变态，而南方鳗鲡和南方鳗鲡则在孵化后90-160天开始变态。 ...更多信息 effenbachi收集在新西兰，变质年龄较大，分别为204和248天。温带鳗鱼（平均268和297天）的年龄也比热带鳗鱼（116-195天）大。这些早期生活史的差异可能是由热带鳗类的本地洄游向温带鳗类的远距离洄游进化过程中的一种适应。2.进化：（1）系统发育分析：系统发育分析表明，安圭拉在白垩纪起源于热带地区，安圭拉和长喙安圭拉的祖先最晚在35 Ma前从印度洋-太平洋经特提斯海进入大西洋。(2)寄生虫学分析：本文报道了在澳洲鳗鲡（A.australis）和莱氏鳗鲡（A. reinhardti）鳃上发现的两种单殖吸虫--拟指环虫（Pseudodactylogyrus）新种。它们似乎是澳大利亚特有的，在形态和遗传上与感染日本鳗鱼的最近亲属不同，表明在东亚的日本拟指环虫与澳大利亚的两个物种分离期间，拟指环虫与鳗鱼共同进化。少

We made expeditions to a total of 12 countries for 540 days during 1995-1998 fiscal years and obtained the following results. 1. Adaptive significance : (1) Physiological characteristics : Immunohistochemical analysis showed two types of chloride cells in the gill lamella and gill fillament of Anguilla japonica. The former was activated in freshwater habitat and the latter, in the marine habitat following the downstream migration to the sea. (2) Migratory behavior : The survey on the inshore migration of tropical glass eels during 1995-1998 revealed that three species (A.celebesensis, A.marmorata and A.bicolor pacifica) occurred at the mouth of Poigar River, Sulawesi Island, Indonesia. The former two migrated almost throughout the year with the peak season in June and the last occurred in Jan., Mar., Apr., Oct. and Dec.. Analyses on otolith microstructure and Sr/Ca ratio suggested that tropical eels metaborphose at 90-160 days after hatching while teperate species, A.australis and A.di … More effenbachi collected in New Zealand, metamorphosed at older ages, 204 and 248 days, respectively. Age at recruitment to freshwater was also older in temperate eels (268 and 297 days in mean) than those in tropical eels (116-195 days). These differences in early life history of eels might be an adaptation which was caused on the evolutional process from local migaration in tropical eels to long distance migration in temperate species. 2. Evolition : (1) Phylogenetic analysis : Phylogenetic analysis on mtDNA data set suggested that Anguilla originated in tropical area in the Cretaceous and that the ancestor of A.anguilla and A.rostrata would dispersed from the Indo-Pacific into the Atlantic Ocean through the Tethys Sea at latest 35 Ma ago. (2) Parasitological analysis : Two new species of Pseudodactylogyrus, monogenean parasites, were found on the gills of the two Australian eels, A.australis and A.reinhardti. They appear to be endemic to Australia, distinct morphologi- cally and genetically from their nearest relatives infecting the Japanese eel, indicating that Pseudodactylogyrus has coevolved with eels during the isolation of A.japonica in eastern Asia from the two species in Australia. Less