Littoral chydorids were sampled with a bottom sledge in Takvatn, a 15 km2 north Norwegian oligotrophic lake with poor vegetation Three out of eight recorded species of chydorids were common, with abundance minima in late summer and maxima in autumn Eurycercus lamellatus (O F Muller, 1776) and Acroperus harpae (Baird, 1835) were monocyclic, whereas Chydorus sphaericus (O F Muller, 1776) was seemingly acyclic Females of E lamellatus appeared in early June and grew to maximum sizes of 2–2 5 mm in early August Parthenogenesis started in late July and two summer generations could be distinguished by size distributions Gamogenesis took place in September Acroperus harpae females appeared in early June and grew to maximum sizes of around 0 7 mm in early August Parthenogenesis started in early July and gamogenesis took place in September and October Parthenogenetic females of C sphaericus appeared already at ice-break and had constant sizes of around 0 4 mm through the entire season Males or ephippial females were not observed The acyclic life history may be an adaptation to the challenging environment of this subarctic lake Summer generations could not be distinguished in the two small-sized species, but both populations reached high abundances in autumn The abundance of E lamellatus increased from August, but then decreased, possibly as a result of fish predation We argue that the present results are typical for large oligotrophic lakes in subarctic Europe

中文翻译：

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亚北极欧洲湖中沿岸石斑鱼（枝角目：石斑鱼科）的多样性、丰富度和生活史

在挪威北部一个 15 平方公里、植被贫乏的贫营养湖中，用底部雪橇对沿海乳糜泻进行采样 八分之三记录的乳糜泻物种很常见，在夏末丰度最低，秋季丰度最高 Eurycercus lamellatus (OF Muller, 1776)和 Acroperus harpae (Baird, 1835) 是单环的，而 Chydorus sphaericus (OF Muller,1776) 似乎是无周期的 E lamellatus 的雌性出现在 6 月初，并在 8 月初长到最大尺寸 2-2 5 毫米 孤雌生殖在 7 月下旬开始，两个夏季世代可以通过大小分布来区分 9 月发生 Gamogenesis在 6 月初出现并在 8 月初长到最大约 0 7 毫米 孤雌生殖于 7 月初开始，并在 9 月和 10 月发生单性生殖 C sphaericus 的孤雌生殖雌性已经出现在破冰期，并且具有约 0 4 毫米的恒定大小在整个季节中 没有观察到雄性或雌性雌性 无周期的生活史可能是对这个亚北极湖充满挑战的环境的一种适应 在这两个小型物种中无法区分夏季世代，但两个种群在秋季都达到了高丰度 E lamellatus 的丰度从 8 月开始增加，但随后下降，可能是鱼类捕食的结果 我们认为目前的结果是亚北极地区大型贫营养湖泊的典型结果