Interspecific variation in ephippial size between Daphnia galeata and D. pulicaria in Lake Biwa, Japan
Interspecific variation in ephippial size between Daphnia galeata and D. pulicaria in Lake Biwa, Japan
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日本琵琶湖 Daphnia galeata 和 D. pulicaria 种间尺寸差异
DOI：
10.1007/s10201-020-00646-8
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发表时间：
2020
期刊：
影响因子：
1.6
通讯作者：
Michinobu Kuwae
中科院分区：
文献类型：
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作者：
Narumi Tsugeki;M. Honjo;Michinobu Kuwae
水蚤是湖泊中的关键食草动物，通常会立即产生孵化卵;此外，它们也会产生由一个ephippial外壳包裹的休眠卵，一个加厚的甲壳，允许种群在恶劣的环境条件下生存。为了研究不同亚属水蚤种之间的ephippial形态差异，我们进行了显微镜观察和遗传分析的基础上的线粒体12 S rRNA基因的ephippia从日本琵琶湖的表面沉积物。被鉴定为Daphnia galeata Sars（透明水蚤）的上足的长度和高度分别小于0.82和0.50 mm，而Daphnia pulicaria福布斯（水蚤）的上足的长度和高度分别大于0.87和0.53 mm，这两个物种的上足长度差异显著。结果表明，D. galeata和D.根据上足的大小，可以区分出栖息在琵琶湖的蚤状蚤，其上足的边界长度约为0.86 mm。与此推断相一致，历史资料表明，在20世纪80年代以前，从沉积物柱样中回收的上足长度不超过0.86 mm。galeata为优势种，但2000年后超过阈值，与D. galeata和D.蚤状。
Daphnia, keystone herbivores in lakes, routinely produce immediately hatching eggs; additionally, they also produce resting eggs enveloped by an ephippial case, a thickened carapace that allows population survival under harsh environmental conditions. To examine differences in ephippial morphology between Daphnia species in different subgenera, we conducted microscopic observations and genetic analyses based on the mitochondrial 12S rRNA gene in ephippia from surface sediment in Lake Biwa, Japan. The lengths and heights of ephippia identified as Daphnia galeata Sars (Hyalodaphnia) were less than 0.82 and 0.50 mm, respectively, whereas those of Daphnia pulicaria Forbes (Daphnia) were greater than 0.87 and 0.53 mm, respectively, with the ephippial lengths of the two species differing significantly. The results indicate that D. galeata and D. pulicaria inhabiting Lake Biwa can be distinguished based on ephippium size, with a boundary ephippium length of approximately 0.86 mm. In concordance with this inference, historical data indicated that the length of ephippia recovered from sediment cores did not exceed 0.86 mm prior to the 1980s when D. galeata was the predominant species; however, it exceeded the threshold after 2000, coinciding with the coexistence of D. galeata and D. pulicaria.